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[STM32L1xx] Change SPI clock selection 

Update of STM32L1 family CPI clock selection algo.
Maximum SPI clock is obtained from APB domain clock (based on HAL API).
Then algo sets maximum frequency available below requested frequency
pull/2013/head
Erwan GOURIOU 2016-06-22 14:59:17 +02:00
parent b126d345d1
commit 67e6f729c7
1 changed files with 39 additions and 37 deletions
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76
hal/targets/hal/TARGET_STM/TARGET_STM32L1/spi_api.c
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@ -28,6 +28,7 @@
******************************************************************************* *******************************************************************************
*/ */
#include "mbed_assert.h" #include "mbed_assert.h"
#include "mbed_error.h"
#include "spi_api.h" #include "spi_api.h"
#if DEVICE_SPI #if DEVICE_SPI
@ -177,46 +178,47 @@ void spi_format(spi_t *obj, int bits, int mode, int slave)
init_spi(obj); init_spi(obj);
} }
static const uint16_t baudrate_prescaler_table[] = {SPI_BAUDRATEPRESCALER_2,
SPI_BAUDRATEPRESCALER_4,
SPI_BAUDRATEPRESCALER_8,
SPI_BAUDRATEPRESCALER_16,
SPI_BAUDRATEPRESCALER_32,
SPI_BAUDRATEPRESCALER_64,
SPI_BAUDRATEPRESCALER_128,
SPI_BAUDRATEPRESCALER_256};
void spi_frequency(spi_t *obj, int hz) void spi_frequency(spi_t *obj, int hz)
{ {
// Values depend of PCLK1 and PCLK2: 32 MHz if HSI is used, 24 MHz if HSE is used int spi_hz = 0;
if (SystemCoreClock == 32000000) { // HSI uint8_t prescaler_rank = 0;
if (hz < 250000) {
obj->br_presc = SPI_BAUDRATEPRESCALER_256; // 125 kHz /* Get source clock depending on SPI instance */
} else if ((hz >= 250000) && (hz < 500000)) { switch ((int)obj->spi) {
obj->br_presc = SPI_BAUDRATEPRESCALER_128; // 250 kHz case SPI_1:
} else if ((hz >= 500000) && (hz < 1000000)) { /* SPI_1. Source CLK is PCKL2 */
obj->br_presc = SPI_BAUDRATEPRESCALER_64; // 500 kHz spi_hz = HAL_RCC_GetPCLK2Freq();
} else if ((hz >= 1000000) && (hz < 2000000)) { break;
obj->br_presc = SPI_BAUDRATEPRESCALER_32; // 1 MHz case SPI_2:
} else if ((hz >= 2000000) && (hz < 4000000)) { case SPI_3:
obj->br_presc = SPI_BAUDRATEPRESCALER_16; // 2 MHz /* SPI_2, SPI_3. Source CLK is PCKL1 */
} else if ((hz >= 4000000) && (hz < 8000000)) { spi_hz = HAL_RCC_GetPCLK1Freq();
obj->br_presc = SPI_BAUDRATEPRESCALER_8; // 4 MHz break;
} else if ((hz >= 8000000) && (hz < 16000000)) { default:
obj->br_presc = SPI_BAUDRATEPRESCALER_4; // 8 MHz error("SPI instance not set");
} else { // >= 16000000
obj->br_presc = SPI_BAUDRATEPRESCALER_2; // 16 MHz
}
} else { // 24 MHz - HSE
if (hz < 180000) {
obj->br_presc = SPI_BAUDRATEPRESCALER_256; // 94 kHz
} else if ((hz >= 180000) && (hz < 350000)) {
obj->br_presc = SPI_BAUDRATEPRESCALER_128; // 188 kHz
} else if ((hz >= 350000) && (hz < 750000)) {
obj->br_presc = SPI_BAUDRATEPRESCALER_64; // 375 kHz
} else if ((hz >= 750000) && (hz < 1000000)) {
obj->br_presc = SPI_BAUDRATEPRESCALER_32; // 750 kHz
} else if ((hz >= 1000000) && (hz < 3000000)) {
obj->br_presc = SPI_BAUDRATEPRESCALER_16; // 1.5 MHz
} else if ((hz >= 3000000) && (hz < 6000000)) {
obj->br_presc = SPI_BAUDRATEPRESCALER_8; // 3 MHz
} else if ((hz >= 6000000) && (hz < 12000000)) {
obj->br_presc = SPI_BAUDRATEPRESCALER_4; // 6 MHz
} else { // >= 12000000
obj->br_presc = SPI_BAUDRATEPRESCALER_2; // 12 MHz
}
} }
/* Define pre-scaler in order to get highest available frequency below requested frequency */
while ((spi_hz > hz) && (prescaler_rank < sizeof(baudrate_prescaler_table)/sizeof(baudrate_prescaler_table[0]))){
spi_hz = spi_hz / 2;
prescaler_rank++;
}
if (prescaler_rank <= sizeof(baudrate_prescaler_table)/sizeof(baudrate_prescaler_table[0])) {
obj->br_presc = baudrate_prescaler_table[prescaler_rank-1];
} else {
error("Couldn't setup requested SPI frequency");
}
init_spi(obj); init_spi(obj);
} }