STM32: simple SPI transfer - arm

Question

I am working with a STM32F3DISCOVERY board and I'm trying to dive a bit deeper into the abstractions of the HAL. I made a simple version of a function that transmits data over SPI, sadly it does not work (at least the DAC I'm sending it to does not change state) and I'm not sure what I am missing there. Maybe there's also something in the initialization code that doesn't work with my simple version. I'd be happy for any guidance or references I could check. Thank you!
#include <stm32f3xx_hal.h>
#define PINS_SPI GPIO_PIN_5 | GPIO_PIN_7
#define GPIO_PORT GPIOA
/* This is the simplest function I could come up with to do the transfer but I'm clearly missing something here */
uint8_t SPI_SendReceive(SPI_HandleTypeDef *hspi, uint8_t data) {
/* Loop while DR register in not empty */
while ((hspi->Instance->SR & SPI_FLAG_TXE) == RESET) {
}
/* Send data through the SPI1 peripheral */
hspi->Instance->DR = data;
/* Wait to receive data */
while ((hspi->Instance->SR & SPI_FLAG_RXNE) == RESET) {
}
return hspi->Instance->DR;
}
int main() {
HAL_Init();
__HAL_RCC_GPIOA_CLK_ENABLE();
__HAL_RCC_SPI1_CLK_ENABLE();
static SPI_HandleTypeDef spi = {.Instance = SPI1};
spi.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_256;
spi.Init.Direction = SPI_DIRECTION_2LINES;
spi.Init.CLKPhase = SPI_PHASE_1EDGE;
spi.Init.CLKPolarity = SPI_POLARITY_LOW;
spi.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
spi.Init.DataSize = SPI_DATASIZE_8BIT;
spi.Init.FirstBit = SPI_FIRSTBIT_MSB;
spi.Init.NSS = SPI_NSS_HARD_OUTPUT;
spi.Init.TIMode = SPI_TIMODE_DISABLE;
spi.Init.Mode = SPI_MODE_MASTER;
HAL_SPI_Init(&spi);
__HAL_SPI_ENABLE(&spi);
GPIO_InitTypeDef GPIO_InitStruct;
GPIO_InitStruct.Pin = PINS_SPI;
GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
GPIO_InitStruct.Pull = GPIO_PULLUP;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
GPIO_InitStruct.Alternate = GPIO_AF5_SPI1;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
GPIO_InitStruct.Pin = GPIO_PIN_4;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
/* TI 8564 DAC Settings */
uint8_t cmd1 = 0b00010000;
/* DAC output value (16-bit) */
uint16_t cmd23 = 0;
uint8_t cmd2 = cmd23 >> 8;
uint8_t cmd3 = cmd23 & 0xff;
uint8_t command[3] = {cmd1, cmd2, cmd3};
while (true) {
HAL_GPIO_WritePin(GPIOA, GPIO_PIN_4, GPIO_PIN_RESET);
/* This does not work :( */
SPI_SendReceive(&spi, command[0]);
SPI_SendReceive(&spi, command[1]);
SPI_SendReceive(&spi, command[2]);
/* This works! When commenting in the lines above and commenting this out */
/* HAL_SPI_Transmit(&spi, command, 3, HAL_MAX_DELAY); */
HAL_GPIO_WritePin(GPIOA, GPIO_PIN_4, GPIO_PIN_SET);
HAL_Delay(1000);
}
}

Answer 1

Check the contents of HAL_SPI_Init. Most likely this function calls another function which is supposed to do the low-level initialization, and you're responsible to provide this function yourself. To make it more complex, this alleged second function already has a "dummy" weak alias defined, so the toolchain doesn't return any error but just builds a code unable to do anything.