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STM32: spi_frequency table index fix 

In case of prescaler_rank was 0, a -1 index was being used,
which resulted in initialization of the Init.BaudRatePrescaler with
random values.

Now let's better check index and avoid -1 operation, so that prescaler_rank
can be only from 0 to "last_index".
pull/3759/head
Laurent MEUNIER 2017-02-13 16:15:10 +01:00
parent 65956d108e
commit a8f6970a9d
1 changed files with 12 additions and 7 deletions
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19
targets/TARGET_STM/stm_spi_api.c
View File

@ -291,23 +291,28 @@ void spi_frequency(spi_t *obj, int hz) {
struct spi_s *spiobj = SPI_S(obj);
int spi_hz = 0;
uint8_t prescaler_rank = 0;
uint8_t last_index = (sizeof(baudrate_prescaler_table)/sizeof(baudrate_prescaler_table[0])) - 1;
SPI_HandleTypeDef *handle = &(spiobj->handle);
/* Get the clock of the peripheral */
spi_hz = spi_get_clock_freq(obj);
/* Calculate the spi clock for prescaler_rank 0: SPI_BAUDRATEPRESCALER_2 */
spi_hz = spi_get_clock_freq(obj) / 2;
/* 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]))){
while ((spi_hz > hz) && (prescaler_rank < last_index)) {
spi_hz = spi_hz / 2;
prescaler_rank++;
}
if (prescaler_rank <= sizeof(baudrate_prescaler_table)/sizeof(baudrate_prescaler_table[0])) {
handle->Init.BaudRatePrescaler = baudrate_prescaler_table[prescaler_rank-1];
} else {
error("Couldn't setup requested SPI frequency");
/* Use the best fit pre-scaler */
handle->Init.BaudRatePrescaler = baudrate_prescaler_table[prescaler_rank];
/* In case maximum pre-scaler still gives too high freq, raise an error */
if (spi_hz > hz) {
error("Couldn't set suitable spi freq: request:%d, lowest:%d\r\n", hz, spi_hz);
}
DEBUG_PRINTF("spi_frequency, request:%d, select:%d\r\n", hz, spi_hz);
init_spi(obj);
}