STM32F030 SPI1 enable bit (CR1->SPE) is not set to 1

[SSala.3]

Hi,

I am trying to interface eeprom module with STM32F0308-Disco board using CUBE IDE - HAL library. SPI communication is not working properly, I am getting random values while trying to read the Eeprom ID.

While debugging the code I found that the SPE bit in CR1 register is not set to 1 even after initialization. What could be the issue?

Attaching the code below.

static 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_MASTER;

 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_128;

 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_ENABLE;

 if (HAL_SPI_Init(&hspi1) != HAL_OK)

 {

  Error_Handler();

 }

 /* USER CODE BEGIN SPI1_Init 2 */

 /* USER CODE END SPI1_Init 2 */

}

[waclawek.jan]

> While debugging the code I found that the SPE bit in CR1 register is not set to 1 even after initialization.

Cube is open source, so you can check what HAL_SPI_Init() does. Indeed, it does not enable SPI; the idea is, that it's enabled only when some of the "communication" (HAL_SPI_TransmitXXX()) functions are called.

To reveal what's the problem, observe MISO/MOSI/SCK lines using oscilloscope/logic analyzer.

JW

[TDK]

That's just how the library works.

You can send a zero-length message which has the effect of enabling the peripheral which sets the clock polarity correctly.

HAL_SPI_Transmit(&hspi1, 0, 0, 0);

> I am getting random values

What values are you getting and what values are you expecting instead? Most likely they're not random, but off by a bit or otherwise related.

[SSala.3]

The issue was resolved, I was reading two bytes using the HAL_SPI_Receive which should be 1 byte in my case. As @Community member​ said the SPI is enabled only during the Transmit or receive function is called.

Thank you @Community member​ and @TDK​