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[STM32L0xx] Change SPI clock selection 

Update of STM32L0 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 14:57:55 +02:00
parent e8103fbb94
commit b126d345d1
1 changed files with 39 additions and 17 deletions
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56
hal/targets/hal/TARGET_STM/TARGET_STM32L0/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
@ -176,27 +177,48 @@ 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)
{ {
// Note: The frequencies are obtained with SPI1 clock = 32 MHz (APB2 clock) int spi_hz = 0;
if (hz < 250000) { uint8_t prescaler_rank = 0;
obj->br_presc = SPI_BAUDRATEPRESCALER_256; // 125 kHz
} else if ((hz >= 250000) && (hz < 500000)) { /* Get source clock depending on SPI instance */
obj->br_presc = SPI_BAUDRATEPRESCALER_128; // 250 kHz switch ((int)obj->spi) {
} else if ((hz >= 500000) && (hz < 1000000)) { case SPI_1:
obj->br_presc = SPI_BAUDRATEPRESCALER_64; // 500 kHz /* SPI_1. Source CLK is PCKL2 */
} else if ((hz >= 1000000) && (hz < 2000000)) { spi_hz = HAL_RCC_GetPCLK2Freq();
obj->br_presc = SPI_BAUDRATEPRESCALER_32; // 1 MHz break;
} else if ((hz >= 2000000) && (hz < 4000000)) { #if defined(SPI2_BASE)
obj->br_presc = SPI_BAUDRATEPRESCALER_16; // 2 MHz case SPI_2:
} else if ((hz >= 4000000) && (hz < 8000000)) { /* SPI_2. Source CLK is PCKL1 */
obj->br_presc = SPI_BAUDRATEPRESCALER_8; // 4 MHz spi_hz = HAL_RCC_GetPCLK1Freq();
} else if ((hz >= 8000000) && (hz < 16000000)) { break;
obj->br_presc = SPI_BAUDRATEPRESCALER_4; // 8 MHz #endif
} else { // >= 16000000 default:
obj->br_presc = SPI_BAUDRATEPRESCALER_2; // 16 MHz error("SPI instance not set");
} }
/* 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);
} }