STM32 SPI slave mode doesn't transmit properly - stm32

Question

I am using an STM32G030C8T6 as an SPI (Slave device) which receives characters from a Raspberry pi (Master device), receiving works perfectly! no problems there, however when i try to send data from STM32 to Pi, it seems that the STM32 gets stuck for a while and Pi rx buffer is filled with only one bit in repeat e.g., if i send char buf[6] = {0,1,2,3,4,5}; Pi receives (111111) or (333333) depending on how many characters i am sending.
What do i actually want to do?
I want to transmit ADC data from STM32(slave mode) to Pi(master mode), so far it only receives one bit i repeat.
Can someone please help me achieve this?
Here's my SPI config:
void MX_SPI1_Init(void)
{
/* USER CODE BEGIN SPI1_Init 0 */
/* USER CODE END SPI1_Init 0 */
/* USER CODE BEGIN SPI1_Init 1 */
/* USER CODE END SPI1_Init 1 */
/* SPI1 parameter configuration*/
hspi1.Instance = SPI1;
hspi1.Init.Mode = SPI_MODE_SLAVE;
hspi1.Init.Direction = SPI_DIRECTION_2LINES;
hspi1.Init.DataSize = SPI_DATASIZE_8BIT;
hspi1.Init.CLKPolarity = SPI_POLARITY_LOW;
hspi1.Init.CLKPhase = SPI_PHASE_1EDGE;
hspi1.Init.NSS = SPI_NSS_SOFT;
hspi1.Init.FirstBit = SPI_FIRSTBIT_MSB;
hspi1.Init.TIMode = SPI_TIMODE_DISABLE;
hspi1.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
hspi1.Init.CRCPolynomial = 7;
hspi1.Init.CRCLength = SPI_CRC_LENGTH_DATASIZE;
hspi1.Init.NSSPMode = SPI_NSS_PULSE_DISABLE;
if (HAL_SPI_Init(&hspi1) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN SPI1_Init 2 */
/* USER CODE END SPI1_Init 2 */
}
then the functions to read characters, send data and string
char SPI_read(void)
{
// SPI1->SR is the STATUS REGISTER on SPI1 Bus
// SPI1->DR is the DATA REGISTER on SPI1 Bus
char data;
while(!(SPI1->SR & SPI_SR_RXNE));
while(SPI1->SR & SPI_SR_BSY);
data = SPI1->DR;
printmsg("%c",data);
return data;
}
void spi_Send(char caracSend)
{
while(!(SPI1->SR & SPI_SR_TXE));
SPI1->DR = caracSend;
}
void spi_send_string(char* stringSend)
{
int i=0;
unsigned int sizeChar = 0;
sizeChar = strlen(stringSend);
__NOP();
for(i=0;i<sizeChar;i++)
{
spi_Send(stringSend[i]);
}
}
Here's my function to receive data from Pi which i call in the main while loop.
void SPI_Receive_Commands(void)
{
while(HAL_GPIO_ReadPin(SPI_SS_GPIO_Port, SPI_SS_Pin) == GPIO_PIN_RESET);
{
HAL_SPI_Receive(&hspi1, (uint8_t *)spi_buf, 10, 100);
if(spi_buf[0] == 'v')
{
memset(spi_buf,'*',10);
printmsg("Character V received\r\n");
Battery_Voltage();
spi_send_string(batteryVoltage);
spi_Send('v');
printmsg("Sending battery voltage\r\n");
}
}
}
Thank you so much for helping me out in advance.

Answer 1

Initialisation. You need set the RX FIFO threshold to 1/4 as you read and write bytes. I do not know how to do it in HAL. Register level simply set FRXTH bit in the CR2 register
DR register has to be accessed in 8 bits operations.
You do not need to use BSY bit in polling mode unless you want to disable the SPI peripheral.
void spi_Send(char caracSend)
{
while(!(SPI1->SR & SPI_SR_TXE));
*(volatile uint8_t *)&SPI1->DR = caracSend;
}
void spi_send_string(char* str)
{
if(str) while(*str) spi_Send(*str++);
}
char SPI_read(void)
{
char data;
while(!(SPI1->SR & SPI_SR_RXNE));
data = *(volatile uint8_t *)&SPI1->DR;
return data;
}
Remember that raspberry pi HAS TO send dummy data to allow slave to send information. Slave does not generate the clock signal and clock has to be supplied by the Master