diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC15XX/spi_api.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC15XX/spi_api.c
index 774e347dc4..c378d9cc4c 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC15XX/spi_api.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC15XX/spi_api.c
@@ -43,7 +43,8 @@ static const SWM_Map SWM_SPI_MISO[] = {
 
 // bit flags for used SPIs
 static unsigned char spi_used = 0;
-static int get_available_spi(void) {
+static int get_available_spi(void)
+{
     int i;
     for (i=0; i<2; i++) {
         if ((spi_used & (1 << i)) == 0)
@@ -55,7 +56,8 @@ static int get_available_spi(void) {
 static inline void spi_disable(spi_t *obj);
 static inline void spi_enable(spi_t *obj);
 
-void spi_init(spi_t *obj, PinName mosi, PinName miso, PinName sclk, PinName ssel) {
+void spi_init(spi_t *obj, PinName mosi, PinName miso, PinName sclk, PinName ssel)
+{
     int spi_n = get_available_spi();
     if (spi_n == -1) {
         error("No available SPI");
@@ -63,24 +65,24 @@ void spi_init(spi_t *obj, PinName mosi, PinName miso, PinName sclk, PinName ssel
 
     obj->spi_n = spi_n;
     spi_used |= (1 << spi_n);
-    
+
     obj->spi = (spi_n) ? (LPC_SPI0_Type *)(LPC_SPI1_BASE) : (LPC_SPI0_Type *)(LPC_SPI0_BASE);
-    
+
     const SWM_Map *swm;
     uint32_t regVal;
-    
+
     if (sclk != NC) {
         swm = &SWM_SPI_SCLK[obj->spi_n];
         regVal = LPC_SWM->PINASSIGN[swm->n] & ~(0xFF << swm->offset);
         LPC_SWM->PINASSIGN[swm->n] = regVal |  (sclk   << swm->offset);
     }
-    
+
     if (mosi != NC) {
         swm = &SWM_SPI_MOSI[obj->spi_n];
         regVal = LPC_SWM->PINASSIGN[swm->n] & ~(0xFF << swm->offset);
         LPC_SWM->PINASSIGN[swm->n] = regVal |  (mosi   << swm->offset);
     }
-    
+
     if (miso != NC) {
         swm = &SWM_SPI_MISO[obj->spi_n];
         regVal = LPC_SWM->PINASSIGN[swm->n] & ~(0xFF << swm->offset);
@@ -95,22 +97,12 @@ void spi_init(spi_t *obj, PinName mosi, PinName miso, PinName sclk, PinName ssel
 
     // clear interrupts
     obj->spi->INTENCLR = 0x3f;
-    
-    // enable power and clocking
 
-    switch (obj->spi_n) {
-        case 0:
-            LPC_SYSCON->SYSAHBCLKCTRL1 |= (0x1<<9);
-            LPC_SYSCON->PRESETCTRL1 |= (0x1<<9);
-            LPC_SYSCON->PRESETCTRL1 &= ~(0x1<<9);
-            break;
-        case 1:
-            LPC_SYSCON->SYSAHBCLKCTRL1 |= (0x1<<10);
-            LPC_SYSCON->PRESETCTRL1 |= (0x1<<10);
-            LPC_SYSCON->PRESETCTRL1 &= ~(0x1<<10);
-            break;
-    }
-    
+    // enable power and clocking
+    LPC_SYSCON->SYSAHBCLKCTRL1 |=  (0x1 << (obj->spi_n + 9));
+    LPC_SYSCON->PRESETCTRL1    |=  (0x1 << (obj->spi_n + 9));
+    LPC_SYSCON->PRESETCTRL1    &= ~(0x1 << (obj->spi_n + 9));
+
     // set default format and frequency
     if (ssel == NC) {
         spi_format(obj, 8, 0, 0);  // 8 bits, mode 0, master
@@ -118,96 +110,111 @@ void spi_init(spi_t *obj, PinName mosi, PinName miso, PinName sclk, PinName ssel
         spi_format(obj, 8, 0, 1);  // 8 bits, mode 0, slave
     }
     spi_frequency(obj, 1000000);
-    
+
     // enable the spi channel
     spi_enable(obj);
 }
 
-void spi_free(spi_t *obj) {}
+void spi_free(spi_t *obj)
+{
+}
 
-void spi_format(spi_t *obj, int bits, int mode, int slave) {
+void spi_format(spi_t *obj, int bits, int mode, int slave)
+{
     spi_disable(obj);
     MBED_ASSERT((bits >= 1 && bits <= 16) && (mode >= 0 && mode <= 3));
-    
+
     int polarity = (mode & 0x2) ? 1 : 0;
     int phase = (mode & 0x1) ? 1 : 0;
-    
+
     // set it up
     int LEN = bits - 1;             // LEN  - Data Length
     int CPOL = (polarity) ? 1 : 0;  // CPOL - Clock Polarity select
     int CPHA = (phase) ? 1 : 0;     // CPHA - Clock Phase select
-    
+
     uint32_t tmp = obj->spi->CFG;
     tmp &= ~((1 << 5) | (1 << 4) | (1 << 2));
     tmp |= (CPOL << 5) | (CPHA << 4) | ((slave ? 0 : 1) << 2);
     obj->spi->CFG = tmp;
-    
+
     // select frame length
     tmp = obj->spi->TXDATCTL;
     tmp &= ~(0xf << 24);
     tmp |= (LEN << 24);
     obj->spi->TXDATCTL = tmp;
-    
+
     spi_enable(obj);
 }
 
-void spi_frequency(spi_t *obj, int hz) {
+void spi_frequency(spi_t *obj, int hz)
+{
     spi_disable(obj);
-    
-    uint32_t PCLK = SystemCoreClock;
-    
-    obj->spi->DIV = PCLK/hz - 1;
+
+    // rise DIV value if it cannot be divided
+    obj->spi->DIV = (SystemCoreClock + (hz - 1))/hz - 1;
     obj->spi->DLY = 0;
+
     spi_enable(obj);
 }
 
-static inline void spi_disable(spi_t *obj) {
+static inline void spi_disable(spi_t *obj)
+{
     obj->spi->CFG &= ~(1 << 0);
 }
 
-static inline void spi_enable(spi_t *obj) {
+static inline void spi_enable(spi_t *obj)
+{
     obj->spi->CFG |= (1 << 0);
 }
 
-static inline int spi_readable(spi_t *obj) {
+static inline int spi_readable(spi_t *obj)
+{
     return obj->spi->STAT & (1 << 0);
 }
 
-static inline int spi_writeable(spi_t *obj) {
+static inline int spi_writeable(spi_t *obj)
+{
     return obj->spi->STAT & (1 << 1);
 }
 
-static inline void spi_write(spi_t *obj, int value) {
+static inline void spi_write(spi_t *obj, int value)
+{
     while (!spi_writeable(obj));
     // end of transfer
     obj->spi->TXDATCTL |= (1 << 20);
     obj->spi->TXDAT = value;
 }
 
-static inline int spi_read(spi_t *obj) {
+static inline int spi_read(spi_t *obj)
+{
     while (!spi_readable(obj));
     return obj->spi->RXDAT;
 }
 
-int spi_busy(spi_t *obj) {
+int spi_busy(spi_t *obj)
+{
     // checking RXOV(Receiver Overrun interrupt flag)
     return obj->spi->STAT & (1 << 2);
-    }
+}
 
-int spi_master_write(spi_t *obj, int value) {
+int spi_master_write(spi_t *obj, int value)
+{
     spi_write(obj, value);
     return spi_read(obj);
 }
 
-int spi_slave_receive(spi_t *obj) {
+int spi_slave_receive(spi_t *obj)
+{
     return (spi_readable(obj) && !spi_busy(obj)) ? (1) : (0);
 }
 
-int spi_slave_read(spi_t *obj) {
+int spi_slave_read(spi_t *obj)
+{
     return obj->spi->RXDAT;
 }
 
-void spi_slave_write(spi_t *obj, int value) {
+void spi_slave_write(spi_t *obj, int value)
+{
     while (spi_writeable(obj) == 0) ;
     obj->spi->TXDAT = value;
 }