diff --git a/drivers/SPI.cpp b/drivers/SPI.cpp
index 465594dcdd..fc3764e241 100644
--- a/drivers/SPI.cpp
+++ b/drivers/SPI.cpp
@@ -32,7 +32,8 @@ SPI::SPI(PinName mosi, PinName miso, PinName sclk, PinName ssel) :
 #endif
         _bits(8),
         _mode(0),
-        _hz(1000000) {
+        _hz(1000000),
+        _write_fill(SPI_FILL_CHAR) {
     // No lock needed in the constructor
 
     spi_init(&_spi, mosi, miso, sclk, ssel);
@@ -102,7 +103,7 @@ int SPI::write(int value) {
 int SPI::write(const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
     lock();
     _acquire();
-    int ret = spi_master_block_write(&_spi, tx_buffer, tx_length, rx_buffer, rx_length);
+    int ret = spi_master_block_write(&_spi, tx_buffer, tx_length, rx_buffer, rx_length, _write_fill);
     unlock();
     return ret;
 }
@@ -115,6 +116,12 @@ void SPI::unlock() {
     _mutex->unlock();
 }
 
+void SPI::set_default_write_value(char data) {
+    lock();
+    _write_fill = data;
+    unlock();
+}
+
 #if DEVICE_SPI_ASYNCH
 
 int SPI::transfer(const void *tx_buffer, int tx_length, void *rx_buffer, int rx_length, unsigned char bit_width, const event_callback_t& callback, int event)
diff --git a/drivers/SPI.h b/drivers/SPI.h
index 52df60f62c..645243070d 100644
--- a/drivers/SPI.h
+++ b/drivers/SPI.h
@@ -143,6 +143,15 @@ public:
      */
     virtual void unlock(void);
 
+    /** Set default write data
+      * SPI requires the master to send some data during a read operation.
+      * Different devices may require different default byte values.
+      * For example: A SD Card requires default bytes to be 0xFF.
+      *
+      * @param data    Default character to be transmitted while read operation
+      */
+    void set_default_write_value(char data);
+
 #if DEVICE_SPI_ASYNCH
 
     /** Start non-blocking SPI transfer using 8bit buffers.
@@ -271,6 +280,7 @@ protected:
     int _bits;
     int _mode;
     int _hz;
+    char _write_fill;
 
 private:
     /* Private acquire function without locking/unlocking
diff --git a/hal/spi_api.h b/hal/spi_api.h
index 368e7b0e69..7fbcf223e4 100644
--- a/hal/spi_api.h
+++ b/hal/spi_api.h
@@ -33,6 +33,7 @@
 #define SPI_EVENT_INTERNAL_TRANSFER_COMPLETE (1 << 30) // Internal flag to report that an event occurred
 
 #define SPI_FILL_WORD         (0xFFFF)
+#define SPI_FILL_CHAR         (0xFF)
 
 #if DEVICE_SPI_ASYNCH
 /** Asynch SPI HAL structure
@@ -122,16 +123,17 @@ int  spi_master_write(spi_t *obj, int value);
  *  tx_length and rx_length. The bytes written will be padded with the
  *  value 0xff.
  *
- * @param[in] obj       The SPI peripheral to use for sending
- * @param[in] tx_buffer Pointer to the byte-array of data to write to the device
- * @param[in] tx_length Number of bytes to write, may be zero
- * @param[in] rx_buffer Pointer to the byte-array of data to read from the device
- * @param[in] rx_length Number of bytes to read, may be zero
+ * @param[in] obj        The SPI peripheral to use for sending
+ * @param[in] tx_buffer  Pointer to the byte-array of data to write to the device
+ * @param[in] tx_length  Number of bytes to write, may be zero
+ * @param[in] rx_buffer  Pointer to the byte-array of data to read from the device
+ * @param[in] rx_length  Number of bytes to read, may be zero
+ * @param[in] write_fill Default data transmitted while performing a read
  * @returns
  *      The number of bytes written and read from the device. This is
  *      maximum of tx_length and rx_length.
  */
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length);
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length, char write_fill);
 
 /** Check if a value is available to read
  *
diff --git a/targets/TARGET_ARM_SSG/TARGET_BEETLE/spi_api.c b/targets/TARGET_ARM_SSG/TARGET_BEETLE/spi_api.c
index a54337f798..8385ecedae 100644
--- a/targets/TARGET_ARM_SSG/TARGET_BEETLE/spi_api.c
+++ b/targets/TARGET_ARM_SSG/TARGET_BEETLE/spi_api.c
@@ -262,11 +262,12 @@ int spi_master_write(spi_t *obj, int value) {
     return data;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_ARM_SSG/TARGET_CM3DS_MPS2/spi_api.c b/targets/TARGET_ARM_SSG/TARGET_CM3DS_MPS2/spi_api.c
index b42079e3a8..cb2d6bfc0b 100644
--- a/targets/TARGET_ARM_SSG/TARGET_CM3DS_MPS2/spi_api.c
+++ b/targets/TARGET_ARM_SSG/TARGET_CM3DS_MPS2/spi_api.c
@@ -256,13 +256,13 @@ int spi_master_write(spi_t *obj, int value)
 }
 
 int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
-                           char *rx_buffer, int rx_length)
+                           char *rx_buffer, int rx_length, char write_fill)
 {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
     char out, in;
 
     for (int i = 0; i < total; i++) {
-        out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        out = (i < tx_length) ? tx_buffer[i] : write_fill;
         in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_ARM_SSG/TARGET_IOTSS/spi_api.c b/targets/TARGET_ARM_SSG/TARGET_IOTSS/spi_api.c
index f40445c90f..88b2e89be2 100644
--- a/targets/TARGET_ARM_SSG/TARGET_IOTSS/spi_api.c
+++ b/targets/TARGET_ARM_SSG/TARGET_IOTSS/spi_api.c
@@ -268,11 +268,12 @@ int spi_master_write(spi_t *obj, int value) {
     return (ssp_read(obj));
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_ARM_SSG/TARGET_MPS2/spi_api.c b/targets/TARGET_ARM_SSG/TARGET_MPS2/spi_api.c
index 3e2dcd9b13..affd5b2514 100644
--- a/targets/TARGET_ARM_SSG/TARGET_MPS2/spi_api.c
+++ b/targets/TARGET_ARM_SSG/TARGET_MPS2/spi_api.c
@@ -268,11 +268,12 @@ int spi_master_write(spi_t *obj, int value) {
     return (ssp_read(obj));
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Atmel/TARGET_SAM_CortexM0P/spi_api.c b/targets/TARGET_Atmel/TARGET_SAM_CortexM0P/spi_api.c
index 09c4cbc3c4..9da9a458dd 100644
--- a/targets/TARGET_Atmel/TARGET_SAM_CortexM0P/spi_api.c
+++ b/targets/TARGET_Atmel/TARGET_SAM_CortexM0P/spi_api.c
@@ -555,11 +555,12 @@ int spi_master_write(spi_t *obj, int value)
     return rx_data;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Atmel/TARGET_SAM_CortexM4/spi_api.c b/targets/TARGET_Atmel/TARGET_SAM_CortexM4/spi_api.c
index f2b2cf183d..13a326eab3 100644
--- a/targets/TARGET_Atmel/TARGET_SAM_CortexM4/spi_api.c
+++ b/targets/TARGET_Atmel/TARGET_SAM_CortexM4/spi_api.c
@@ -296,11 +296,12 @@ int  spi_master_write(spi_t *obj, int value)
     return 0;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char _write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : _write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Freescale/TARGET_K20XX/spi_api.c b/targets/TARGET_Freescale/TARGET_K20XX/spi_api.c
index 9dce8ddf46..391615e368 100644
--- a/targets/TARGET_Freescale/TARGET_K20XX/spi_api.c
+++ b/targets/TARGET_Freescale/TARGET_K20XX/spi_api.c
@@ -140,11 +140,12 @@ int spi_master_write(spi_t *obj, int value) {
     return obj->spi->POPR;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Freescale/TARGET_KLXX/TARGET_KL05Z/spi_api.c b/targets/TARGET_Freescale/TARGET_KLXX/TARGET_KL05Z/spi_api.c
index a5ca202df3..1e9de30ce5 100644
--- a/targets/TARGET_Freescale/TARGET_KLXX/TARGET_KL05Z/spi_api.c
+++ b/targets/TARGET_Freescale/TARGET_KLXX/TARGET_KL05Z/spi_api.c
@@ -141,11 +141,12 @@ int spi_master_write(spi_t *obj, int value) {
     return obj->spi->D & 0xff;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Freescale/TARGET_KLXX/TARGET_KL25Z/spi_api.c b/targets/TARGET_Freescale/TARGET_KLXX/TARGET_KL25Z/spi_api.c
index 4a5ddf7814..cfbc20384c 100644
--- a/targets/TARGET_Freescale/TARGET_KLXX/TARGET_KL25Z/spi_api.c
+++ b/targets/TARGET_Freescale/TARGET_KLXX/TARGET_KL25Z/spi_api.c
@@ -120,11 +120,12 @@ int spi_master_write(spi_t *obj, int value) {
     return obj->spi->D & 0xff;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Freescale/TARGET_KLXX/TARGET_KL26Z/spi_api.c b/targets/TARGET_Freescale/TARGET_KLXX/TARGET_KL26Z/spi_api.c
index 0d75441a43..3d9b072b77 100644
--- a/targets/TARGET_Freescale/TARGET_KLXX/TARGET_KL26Z/spi_api.c
+++ b/targets/TARGET_Freescale/TARGET_KLXX/TARGET_KL26Z/spi_api.c
@@ -199,11 +199,12 @@ int spi_master_write(spi_t *obj, int value) {
     return ret;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Freescale/TARGET_KLXX/TARGET_KL46Z/spi_api.c b/targets/TARGET_Freescale/TARGET_KLXX/TARGET_KL46Z/spi_api.c
index 0d75441a43..3d9b072b77 100644
--- a/targets/TARGET_Freescale/TARGET_KLXX/TARGET_KL46Z/spi_api.c
+++ b/targets/TARGET_Freescale/TARGET_KLXX/TARGET_KL46Z/spi_api.c
@@ -199,11 +199,12 @@ int spi_master_write(spi_t *obj, int value) {
     return ret;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_K66F/spi_api.c b/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_K66F/spi_api.c
index 67d692f85e..8a65bd4f22 100644
--- a/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_K66F/spi_api.c
+++ b/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_K66F/spi_api.c
@@ -118,11 +118,12 @@ int spi_master_write(spi_t *obj, int value)
     return rx_data & 0xffff;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_K82F/spi_api.c b/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_K82F/spi_api.c
index 67d692f85e..8a65bd4f22 100644
--- a/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_K82F/spi_api.c
+++ b/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_K82F/spi_api.c
@@ -118,11 +118,12 @@ int spi_master_write(spi_t *obj, int value)
     return rx_data & 0xffff;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_KL27Z/spi_api.c b/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_KL27Z/spi_api.c
index 5e4b311d7a..084962073d 100644
--- a/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_KL27Z/spi_api.c
+++ b/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_KL27Z/spi_api.c
@@ -115,11 +115,12 @@ int spi_master_write(spi_t *obj, int value)
     return rx_data & 0xffff;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_KL43Z/spi_api.c b/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_KL43Z/spi_api.c
index 5e4b311d7a..084962073d 100644
--- a/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_KL43Z/spi_api.c
+++ b/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_KL43Z/spi_api.c
@@ -115,11 +115,12 @@ int spi_master_write(spi_t *obj, int value)
     return rx_data & 0xffff;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_KL82Z/spi_api.c b/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_KL82Z/spi_api.c
index 3d1a6af5a6..8bbf7ae247 100644
--- a/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_KL82Z/spi_api.c
+++ b/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_KL82Z/spi_api.c
@@ -117,11 +117,12 @@ int spi_master_write(spi_t *obj, int value)
     return rx_data & 0xffff;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_KW24D/spi_api.c b/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_KW24D/spi_api.c
index 3d1a6af5a6..8bbf7ae247 100644
--- a/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_KW24D/spi_api.c
+++ b/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_KW24D/spi_api.c
@@ -117,11 +117,12 @@ int spi_master_write(spi_t *obj, int value)
     return rx_data & 0xffff;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_KW41Z/spi_api.c b/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_KW41Z/spi_api.c
index 3d1a6af5a6..8bbf7ae247 100644
--- a/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_KW41Z/spi_api.c
+++ b/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_KW41Z/spi_api.c
@@ -117,11 +117,12 @@ int spi_master_write(spi_t *obj, int value)
     return rx_data & 0xffff;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_MCU_K22F/spi_api.c b/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_MCU_K22F/spi_api.c
index 3d1a6af5a6..8bbf7ae247 100644
--- a/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_MCU_K22F/spi_api.c
+++ b/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_MCU_K22F/spi_api.c
@@ -117,11 +117,12 @@ int spi_master_write(spi_t *obj, int value)
     return rx_data & 0xffff;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_MCU_K24F/spi_api.c b/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_MCU_K24F/spi_api.c
index cf301353a6..cc12421e4f 100644
--- a/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_MCU_K24F/spi_api.c
+++ b/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_MCU_K24F/spi_api.c
@@ -127,11 +127,12 @@ int spi_master_write(spi_t *obj, int value)
     return rx_data & 0xffff;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_MCU_K64F/spi_api.c b/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_MCU_K64F/spi_api.c
index 6751b85ea8..d07da22fa8 100644
--- a/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_MCU_K64F/spi_api.c
+++ b/targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_MCU_K64F/spi_api.c
@@ -127,17 +127,17 @@ int spi_master_write(spi_t *obj, int value)
     return rx_data & 0xffff;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
-    DSPI_MasterTransferBlocking(spi_address[obj->spi.instance], &(dspi_transfer_t){
-        .txData = (uint8_t *)tx_buffer,
-        .rxData = (uint8_t *)rx_buffer,
-        .dataSize = total,
-        .configFlags = kDSPI_MasterCtar0 | kDSPI_MasterPcs0 | kDSPI_MasterPcsContinuous,
-    });
-
-    DSPI_ClearStatusFlags(spi_address[obj->spi.instance], kDSPI_RxFifoDrainRequestFlag | kDSPI_EndOfQueueFlag);
+    for (int i = 0; i < total; i++) {
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
+        char in = spi_master_write(obj, out);
+        if (i < rx_length) {
+            rx_buffer[i] = in;
+        }
+    }
 
     return total;
 }
diff --git a/targets/TARGET_Maxim/TARGET_MAX32600/spi_api.c b/targets/TARGET_Maxim/TARGET_MAX32600/spi_api.c
index 2d1ec59712..edf5ab2f13 100644
--- a/targets/TARGET_Maxim/TARGET_MAX32600/spi_api.c
+++ b/targets/TARGET_Maxim/TARGET_MAX32600/spi_api.c
@@ -179,11 +179,12 @@ int spi_master_write(spi_t *obj, int value)
     return result;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Maxim/TARGET_MAX32610/spi_api.c b/targets/TARGET_Maxim/TARGET_MAX32610/spi_api.c
index 2d1ec59712..edf5ab2f13 100644
--- a/targets/TARGET_Maxim/TARGET_MAX32610/spi_api.c
+++ b/targets/TARGET_Maxim/TARGET_MAX32610/spi_api.c
@@ -179,11 +179,12 @@ int spi_master_write(spi_t *obj, int value)
     return result;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Maxim/TARGET_MAX32620/spi_api.c b/targets/TARGET_Maxim/TARGET_MAX32620/spi_api.c
index ed2d986e00..d2a194366d 100644
--- a/targets/TARGET_Maxim/TARGET_MAX32620/spi_api.c
+++ b/targets/TARGET_Maxim/TARGET_MAX32620/spi_api.c
@@ -231,11 +231,12 @@ int spi_master_write(spi_t *obj, int value)
     return spi_master_transaction(obj, value, MXC_S_SPI_FIFO_DIR_BOTH);
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Maxim/TARGET_MAX32625/spi_api.c b/targets/TARGET_Maxim/TARGET_MAX32625/spi_api.c
index 69e9e8eb80..a30e145502 100644
--- a/targets/TARGET_Maxim/TARGET_MAX32625/spi_api.c
+++ b/targets/TARGET_Maxim/TARGET_MAX32625/spi_api.c
@@ -167,11 +167,12 @@ int spi_master_write(spi_t *obj, int value)
     return *req.rx_data;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Maxim/TARGET_MAX32630/spi_api.c b/targets/TARGET_Maxim/TARGET_MAX32630/spi_api.c
index 69e9e8eb80..a30e145502 100644
--- a/targets/TARGET_Maxim/TARGET_MAX32630/spi_api.c
+++ b/targets/TARGET_Maxim/TARGET_MAX32630/spi_api.c
@@ -167,11 +167,12 @@ int spi_master_write(spi_t *obj, int value)
     return *req.rx_data;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_NORDIC/TARGET_MCU_NRF51822/spi_api.c b/targets/TARGET_NORDIC/TARGET_MCU_NRF51822/spi_api.c
index d6cc309992..b1f354e77e 100755
--- a/targets/TARGET_NORDIC/TARGET_MCU_NRF51822/spi_api.c
+++ b/targets/TARGET_NORDIC/TARGET_MCU_NRF51822/spi_api.c
@@ -263,11 +263,12 @@ int spi_master_write(spi_t *obj, int value)
     return spi_read(obj);
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_NORDIC/TARGET_NRF5/spi_api.c b/targets/TARGET_NORDIC/TARGET_NRF5/spi_api.c
index 1639279f7c..a44533ec54 100644
--- a/targets/TARGET_NORDIC/TARGET_NRF5/spi_api.c
+++ b/targets/TARGET_NORDIC/TARGET_NRF5/spi_api.c
@@ -487,11 +487,12 @@ int spi_master_write(spi_t *obj, int value)
     return p_spi_info->rx_buf;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_NUVOTON/TARGET_M451/spi_api.c b/targets/TARGET_NUVOTON/TARGET_M451/spi_api.c
index e67c1dbd76..dce7661584 100644
--- a/targets/TARGET_NUVOTON/TARGET_M451/spi_api.c
+++ b/targets/TARGET_NUVOTON/TARGET_M451/spi_api.c
@@ -241,11 +241,12 @@ int spi_master_write(spi_t *obj, int value)
     return value2;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_NUVOTON/TARGET_NUC472/spi_api.c b/targets/TARGET_NUVOTON/TARGET_NUC472/spi_api.c
index 74a728fd1e..7377915afc 100644
--- a/targets/TARGET_NUVOTON/TARGET_NUC472/spi_api.c
+++ b/targets/TARGET_NUVOTON/TARGET_NUC472/spi_api.c
@@ -244,11 +244,12 @@ int spi_master_write(spi_t *obj, int value)
     return value2;
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_NXP/TARGET_LPC11U6X/spi_api.c b/targets/TARGET_NXP/TARGET_LPC11U6X/spi_api.c
index 2671cb29ba..95c647c74c 100644
--- a/targets/TARGET_NXP/TARGET_LPC11U6X/spi_api.c
+++ b/targets/TARGET_NXP/TARGET_LPC11U6X/spi_api.c
@@ -190,11 +190,12 @@ int spi_master_write(spi_t *obj, int value) {
     return ssp_read(obj);
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_NXP/TARGET_LPC11UXX/spi_api.c b/targets/TARGET_NXP/TARGET_LPC11UXX/spi_api.c
index 2bce2490e9..024dff60d4 100644
--- a/targets/TARGET_NXP/TARGET_LPC11UXX/spi_api.c
+++ b/targets/TARGET_NXP/TARGET_LPC11UXX/spi_api.c
@@ -156,11 +156,12 @@ int spi_master_write(spi_t *obj, int value) {
     return ssp_read(obj);
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_NXP/TARGET_LPC11XX_11CXX/spi_api.c b/targets/TARGET_NXP/TARGET_LPC11XX_11CXX/spi_api.c
index 80f2a72570..d8595cb22b 100644
--- a/targets/TARGET_NXP/TARGET_LPC11XX_11CXX/spi_api.c
+++ b/targets/TARGET_NXP/TARGET_LPC11XX_11CXX/spi_api.c
@@ -192,11 +192,12 @@ int spi_master_write(spi_t *obj, int value) {
     return ssp_read(obj);
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_NXP/TARGET_LPC13XX/spi_api.c b/targets/TARGET_NXP/TARGET_LPC13XX/spi_api.c
index 2d8c2728ed..5c36ffece0 100644
--- a/targets/TARGET_NXP/TARGET_LPC13XX/spi_api.c
+++ b/targets/TARGET_NXP/TARGET_LPC13XX/spi_api.c
@@ -184,11 +184,12 @@ int spi_master_write(spi_t *obj, int value) {
     return ssp_read(obj);
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_NXP/TARGET_LPC15XX/spi_api.c b/targets/TARGET_NXP/TARGET_LPC15XX/spi_api.c
index 3e2350375a..9d7d8f5f00 100644
--- a/targets/TARGET_NXP/TARGET_LPC15XX/spi_api.c
+++ b/targets/TARGET_NXP/TARGET_LPC15XX/spi_api.c
@@ -248,11 +248,12 @@ int spi_master_write(spi_t *obj, int value)
     return spi_read(obj);
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer,
+                           int tx_length, char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_NXP/TARGET_LPC176X/spi_api.c b/targets/TARGET_NXP/TARGET_LPC176X/spi_api.c
index e01c937a44..ba2bde2989 100644
--- a/targets/TARGET_NXP/TARGET_LPC176X/spi_api.c
+++ b/targets/TARGET_NXP/TARGET_LPC176X/spi_api.c
@@ -190,11 +190,12 @@ int spi_master_write(spi_t *obj, int value) {
     return ssp_read(obj);
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_NXP/TARGET_LPC408X/TARGET_LPC4088/spi_api.c b/targets/TARGET_NXP/TARGET_LPC408X/TARGET_LPC4088/spi_api.c
index efdbd1393c..2af13ff55b 100644
--- a/targets/TARGET_NXP/TARGET_LPC408X/TARGET_LPC4088/spi_api.c
+++ b/targets/TARGET_NXP/TARGET_LPC408X/TARGET_LPC4088/spi_api.c
@@ -197,11 +197,12 @@ int spi_master_write(spi_t *obj, int value) {
     return ssp_read(obj);
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_NXP/TARGET_LPC408X/TARGET_LPC4088_DM/spi_api.c b/targets/TARGET_NXP/TARGET_LPC408X/TARGET_LPC4088_DM/spi_api.c
index b98ab158e4..5797a501cc 100644
--- a/targets/TARGET_NXP/TARGET_LPC408X/TARGET_LPC4088_DM/spi_api.c
+++ b/targets/TARGET_NXP/TARGET_LPC408X/TARGET_LPC4088_DM/spi_api.c
@@ -177,11 +177,12 @@ int spi_master_write(spi_t *obj, int value) {
     return ssp_read(obj);
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_NXP/TARGET_LPC43XX/spi_api.c b/targets/TARGET_NXP/TARGET_LPC43XX/spi_api.c
index 035ca33bd9..03a8049864 100644
--- a/targets/TARGET_NXP/TARGET_LPC43XX/spi_api.c
+++ b/targets/TARGET_NXP/TARGET_LPC43XX/spi_api.c
@@ -196,11 +196,12 @@ int spi_master_write(spi_t *obj, int value) {
     return ssp_read(obj);
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_NXP/TARGET_LPC81X/spi_api.c b/targets/TARGET_NXP/TARGET_LPC81X/spi_api.c
index aabe492697..88ba0a725f 100644
--- a/targets/TARGET_NXP/TARGET_LPC81X/spi_api.c
+++ b/targets/TARGET_NXP/TARGET_LPC81X/spi_api.c
@@ -178,11 +178,12 @@ int spi_master_write(spi_t *obj, int value) {
     return ssp_read(obj);
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_NXP/TARGET_LPC82X/spi_api.c b/targets/TARGET_NXP/TARGET_LPC82X/spi_api.c
index 7e6cc51130..892a123ed1 100644
--- a/targets/TARGET_NXP/TARGET_LPC82X/spi_api.c
+++ b/targets/TARGET_NXP/TARGET_LPC82X/spi_api.c
@@ -174,11 +174,12 @@ int spi_master_write(spi_t *obj, int value)
     return spi_read(obj);
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_ONSEMI/TARGET_NCS36510/spi_api.c b/targets/TARGET_ONSEMI/TARGET_NCS36510/spi_api.c
index db8a906319..646b953796 100644
--- a/targets/TARGET_ONSEMI/TARGET_NCS36510/spi_api.c
+++ b/targets/TARGET_ONSEMI/TARGET_NCS36510/spi_api.c
@@ -83,11 +83,12 @@ int  spi_master_write(spi_t *obj, int value)
     return(fSpiWriteB(obj, value));
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_RENESAS/TARGET_RZ_A1H/spi_api.c b/targets/TARGET_RENESAS/TARGET_RZ_A1H/spi_api.c
index 7c58d0e0ad..a62d8b38db 100644
--- a/targets/TARGET_RENESAS/TARGET_RZ_A1H/spi_api.c
+++ b/targets/TARGET_RENESAS/TARGET_RZ_A1H/spi_api.c
@@ -260,11 +260,12 @@ int spi_master_write(spi_t *obj, int value) {
     return spi_read(obj);
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_RENESAS/TARGET_VK_RZ_A1H/spi_api.c b/targets/TARGET_RENESAS/TARGET_VK_RZ_A1H/spi_api.c
index 3207a1be4d..1464aaacd3 100644
--- a/targets/TARGET_RENESAS/TARGET_VK_RZ_A1H/spi_api.c
+++ b/targets/TARGET_RENESAS/TARGET_VK_RZ_A1H/spi_api.c
@@ -311,11 +311,12 @@ int spi_master_write(spi_t *obj, int value) {
     return spi_read(obj);
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Realtek/TARGET_AMEBA/spi_api.c b/targets/TARGET_Realtek/TARGET_AMEBA/spi_api.c
index cec30a9b3b..90dd72ffd0 100644
--- a/targets/TARGET_Realtek/TARGET_AMEBA/spi_api.c
+++ b/targets/TARGET_Realtek/TARGET_AMEBA/spi_api.c
@@ -241,12 +241,13 @@ int spi_master_write (spi_t *obj, int value)
     return ssi_read(obj);
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length)
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill)
 {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_STM/stm_spi_api.c b/targets/TARGET_STM/stm_spi_api.c
index e64dafc8fa..f231e3dee9 100644
--- a/targets/TARGET_STM/stm_spi_api.c
+++ b/targets/TARGET_STM/stm_spi_api.c
@@ -387,12 +387,13 @@ int spi_master_write(spi_t *obj, int value)
     }
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length)
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill)
 {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_Silicon_Labs/TARGET_EFM32/spi_api.c b/targets/TARGET_Silicon_Labs/TARGET_EFM32/spi_api.c
index a8d5f2842e..3dab2ecd63 100644
--- a/targets/TARGET_Silicon_Labs/TARGET_EFM32/spi_api.c
+++ b/targets/TARGET_Silicon_Labs/TARGET_EFM32/spi_api.c
@@ -391,11 +391,12 @@ int spi_master_write(spi_t *obj, int value)
     return spi_read(obj);
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;
diff --git a/targets/TARGET_WIZNET/TARGET_W7500x/spi_api.c b/targets/TARGET_WIZNET/TARGET_W7500x/spi_api.c
index 913789cbd4..33aa6798a9 100644
--- a/targets/TARGET_WIZNET/TARGET_W7500x/spi_api.c
+++ b/targets/TARGET_WIZNET/TARGET_W7500x/spi_api.c
@@ -183,11 +183,12 @@ int spi_master_write(spi_t *obj, int value) {
     return ssp_read(obj);
 }
 
-int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length) {
+int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
+                           char *rx_buffer, int rx_length, char write_fill) {
     int total = (tx_length > rx_length) ? tx_length : rx_length;
 
     for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : 0xff;
+        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
         char in = spi_master_write(obj, out);
         if (i < rx_length) {
             rx_buffer[i] = in;