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[STM32F0xx] Change SPI clock selection 

Update of STM32F0 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 14:47:47 +02:00
parent b574bb5048
commit 0739d31235
1 changed files with 27 additions and 18 deletions
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45
hal/targets/hal/TARGET_STM/TARGET_STM32F0/spi_api.c
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@ -28,6 +28,7 @@
*******************************************************************************
*/
#include "mbed_assert.h"
#include "mbed_error.h"
#include "spi_api.h"
#if DEVICE_SPI
@ -168,25 +169,33 @@ void spi_format(spi_t *obj, int bits, int mode, int slave) {
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) {
// Note: The frequencies are obtained with SPI clock = 48 MHz (APB clock)
if (hz < 375000) {
obj->br_presc = SPI_BAUDRATEPRESCALER_256; // 188 kHz
} else if ((hz >= 375000) && (hz < 750000)) {
obj->br_presc = SPI_BAUDRATEPRESCALER_128; // 375 kHz
} else if ((hz >= 750000) && (hz < 1000000)) {
obj->br_presc = SPI_BAUDRATEPRESCALER_64; // 750 kHz
} else if ((hz >= 1000000) && (hz < 3000000)) {
obj->br_presc = SPI_BAUDRATEPRESCALER_32; // 1.5 MHz
} else if ((hz >= 3000000) && (hz < 6000000)) {
obj->br_presc = SPI_BAUDRATEPRESCALER_16; // 3 MHz
} else if ((hz >= 6000000) && (hz < 12000000)) {
obj->br_presc = SPI_BAUDRATEPRESCALER_8; // 6 MHz
} else if ((hz >= 12000000) && (hz < 24000000)) {
obj->br_presc = SPI_BAUDRATEPRESCALER_4; // 12 MHz
} else { // >= 24000000
obj->br_presc = SPI_BAUDRATEPRESCALER_2; // 24 MHz
}
int spi_hz = 0;
uint8_t prescaler_rank = 0;
/* SPI_1, SPI_2. Source CLK is PCKL1 */
spi_hz = HAL_RCC_GetPCLK1Freq();
/* 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);
}