How to apply SPI between ESP8266 and STM32f07 with FreeRTOS ?

[CLi H.1]

Recently, I've been worked with the esp8266 and stmf407 discovery board.

I used stm32f407 (master), and connect to esp8266 (slave) via SPI

However, the package I got always missed 1 package. To be more specific, I've tried to send some uint8_t dummy datas, but all the results i got always had a missing part.

Arduino code in esp8266 :

https://github.com/esp8266/Arduino/blob/master/libraries/SPISlave/examples/SPISlave_Test/SPISlave_Test.ino

uvision code :

void StartDefaultTask(void const * argument)
{
  /* USER CODE BEGIN 5 */
  /* Infinite loop */
  for(;;)
  {
	 xSemaphoreTake(DeliverHandle,portMAX_DELAY);
	 xSemaphoreGive(DeliverHandle);
	 osDelay(20);	
	}
}	
 
void StartTask02(void const * argument)
{
  /* USER CODE BEGIN StartTask02 */
  /* Infinite loop */
 
  uint8_t SPI_data[4]={0x01,0x02,0x03,0x04};
  for(;;)
  {
	 xSemaphoreTake(DeliverHandle,portMAX_DELAY);	
	//ss low
	WPC_GPIO_Write_Pin(GPIOA,GPIO_PIN_15, 0x00); //CS = 0
	//spi transmit
	HAL_SPI_Transmit(&hspi2,SPI_data,4,1000);  //Send data
	//ss high
	WPC_GPIO_Write_Pin(GPIOA,GPIO_PIN_15, 0x01); //CS = 1
   }
       osDelay(20);
	xSemaphoreGive(DeliverHandle);
  /* USER CODE END StartTask02 */
	}
}

// I sent SPI_data[4]={0x01,0x02,0x03,0x04} through stm32f407 (master)

// esp8266(slave) debugging return from Arduino

// Nevertheless, the result i got is {0x00, 0x04, 0x03, 0x02}

[TDK · Accepted solution]

The code you're using to send SPI is fine.

The bytes are reversed because the Arduino stores them blindly as they are received and then reads them back in little-endian.

i'm pretty sure the first byte (0x01) is lost because it indicates the status register, although it's quite hard to trace the logic in the Arduino code.

[CLi H.1]

Thanks , you give me a big hand.