SPI issues while using STM32 as slave - stm32

Question

I am using STM32L496RG and have configured it as a slave as follows
/* SPI1 init function */
void MX_SPI1_Init(void)
{
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.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_2;
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();
}
}
I am simply trying to receive data from ESP32 (master) and transmit some data back to ESP32.
void state_standby()
{
#ifdef ESP_PRESENT
if(HAL_SPI_Receive(&hspi1,(uint8_t*)cmd_from_esp, sizeof(cmd_from_esp), 200)!=HAL_OK){
Error_Handler();
}
else{
if (cmd_from_esp[0] == 'S' && cmd_from_esp[1] == 'T' && cmd_from_esp[2] == 'A' && cmd_from_esp[3] == 'R' && cmd_from_esp[4] == 'T'){
if (HAL_SPI_Transmit(&hspi1,(uint8_t*)cmd_from_esp,sizeof(cmd_from_esp),200)!= HAL_OK){
Error_Handler();
}
set_operating_state(TEST_SET);
}
}
#else
set_operating_state(ACTIVE);
flash_page_count = 0;
esp_page_count = 0;
#endif
}
But when I run my code, even though nothing is being received, my code goes into the Error_Handler function inside HAL_SPI_Receiveand goes to state 0x03 (HAL_TIMEOUT). But, nevertheless, when it receives data from ESP32, it does change its state is able to receive the data properly. But the problem I am facing is during my transmission. If I receive START in STM32, I send the same thing back to ESP32, but on the ESP32, I receive STARS. I am not sure if it this is because of HAL_ERROR or due to coding on ESP32 which is below -
for(i = 0; i < MAX_SRV_CLIENTS; i++){
if (serverClients[i] && serverClients[i].connected()){
if(serverClients[i].available()){
//get data from the telnet client and push it to the UART
while(serverClients[i].available())
{
data_array[j]=(serverClients[i].read());
j++;
}
for(m = 0;m<j-2;m++)
vspiCommand();
j=0;
}
}
else {
if (serverClients[i]) {
serverClients[i].stop();
}
}
}
void vspiCommand() {
//Serial.println("in vspi");
//use it as you would the regular arduino SPI API
vspi->beginTransaction(SPISettings(spiClk, MSBFIRST, SPI_MODE0));
digitalWrite(VSPI_SS, LOW); //pull SS slow to prep other end for transfer
{
received_data[m] = vspi->transfer(data_array[m]);
//vspi->transfer(data_array[m]);
// Serial.print(data_array[m]);
// Serial.print('\t');
Serial.print(received_data[m]);
Serial.print('\t');
Serial.println(m);
}
delayMicroseconds(10);
digitalWrite(VSPI_SS, HIGH); //pull ss high to signify end of data transfer
vspi->endTransaction();
}
ESP32 receives data through my phone into data_array buffer and sends it to STM32, which in turn is sending the received data back to ESP32 which it is trying to read.
EDIT - I have modified the code a bit. Now, I am using HAL_SPI_Receive_ITand it stops hanging on that error. Made the following change in Slave side.
while (1)
{
if(HAL_SPI_Receive_IT(&hspi1,(uint8_t*)buffer,sizeof(buffer))!=HAL_OK){
Error_Handler();
}
while(HAL_SPI_GetState(&hspi1) != HAL_SPI_STATE_READY);
}
}
void HAL_SPI_RxCpltCallback(SPI_HandleTypeDef *hspi)
{
if(HAL_SPI_Transmit(&hspi1,(uint8_t*)buffer,sizeof(buffer),200)!=HAL_OK){
Error_Handler();
}
And following changes in master side -
for(i = 0; i < MAX_SRV_CLIENTS; i++){
if (serverClients[i] && serverClients[i].connected()){
if(serverClients[i].available()){
//get data from the telnet client and push it to the UART
while(serverClients[i].available())
{
// read the bytes incoming from the client:
char thisChar = serverClients[i].read();
inData += thisChar;
data_array[j]=thisChar;
j++;
// echo to the server what's been received to confirm we have the string
if (thisChar == '\n')
{
// Serial.print("\nreceived:");
// Serial.print(inData);
for(int i=0;i<(j-2);i++)
{
vspi->beginTransaction(SPISettings(spiClk, MSBFIRST, SPI_MODE0));
digitalWrite(VSPI_SS, LOW); //pull SS slow to prep other end for transfer
{
received_data[i] = vspi->transfer(data_array[i]);
// Serial.print(data_array[m]);
// Serial.print('\t');
Serial.print(received_data[i]);
Serial.print('\t');
Serial.println(i);
}
digitalWrite(VSPI_SS, HIGH); //pull ss high to signify end of data transfer
vspi->endTransaction();
}
serverClients[i].write(received_data, (j-2));
j=0;
}
}
}
The slave(STM32) is able to receive the data properly, but the master(ESP32) receives the proper data only alternately. For example, if I send hello, it receives eeeee(second character of whichever data I'm trying to send). If I send hello again, it receives hello. . (In the image, you can see the slave received data in buffer array and master received data in COM2 port.