Inconsistencies with every HAL_SPI_Transmit() of the same message

[malehakim]

Am getting inconsistencies with every HAL_SPI_Transmit() of the same message in a for-loop. Viewed the result with a logic analyzer and the results are frustrating.

Am just trying to send a Hello World! but on the Logic Analyzer, am getting dummy data.

Am using the STM32F303k8.

Here is my initialized code

char* myTxData = "Hello World!";
 
int main(void)
{
	HAL_Init();
 
	SystemClock_Config();
 
	MX_GPIO_Init();
	MX_SPI1_Init();
 
	// CSN PIN
	HAL_GPIO_WritePin(GPIOA, GPIO_PIN_4, GPIO_PIN_SET);
 
	while (1)
	{
		HAL_GPIO_WritePin(GPIOA, GPIO_PIN_4, GPIO_PIN_RESET);
		HAL_SPI_Transmit(&hspi1, (uint8_t*)myTxData, 12, HAL_MAX_DELAY);
		HAL_GPIO_WritePin(GPIOA, GPIO_PIN_4, GPIO_PIN_SET);
 
		HAL_Delay(100);
	}
}
 
void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
 
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }
 
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSI;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
 
  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
  {
    Error_Handler();
  }
}
 
static void MX_SPI1_Init(void)
{
	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_32;
	hspi1.Init.FirstBit = SPI_FIRSTBIT_MSB;
	hspi1.Init.TIMode = SPI_TIMODE_DISABLE;
	hspi1.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
	hspi1.Init.CRCPolynomial = 10;
  if (HAL_SPI_Init(&hspi1) != HAL_OK)
  {
    Error_Handler();
  }
}

[waclawek.jan]

Zoom in to one of the messages so that individual clocks can be seen.

JW

[malehakim]

Snap view of the individual clocks generated when i send. Am expecting Hello World! in form of ascii but it seems to pick up dummy data that probably from other registers or the data is corrupted in some way

[TDK]

Looks like your CSN line is not behaving correctly. so your bytes are not synchronized to where they should be. I bet an analog capture of that line would show considerable noise, since there are 3 spikes that correspond with a negative edge on MOSI. Are you initializing it as output?

[waclawek.jan]

The transmitted characters as you show them are exactly those corresponding to Hello World!

48 65 6C 6C 6F 20 57 6F 72 6C 64 21

so it's just the LA which is not synchronized - if you set it to synchronize to CSN, then it's as TDK said - either incorrectly initialized pin, incorrectly connected (bad solder joint), or if it is a board with more circuitry on it, it conflicts with some other output.

JW

[malehakim]

Ok, thanks for all the replies. Am now starting to get it working. However, my CSN line is still not behaving well. It spikes up as shown in the snap above. One thing i've seen from all the tutorials is that they never initialize the CSN pin. Its always the MISO, MOSI, SCLK and the GPIO pins as alternate functions. I tried to initialize the GPIO where the CSN pin is so that i try with either pull-up or pull-down resistors but still not getting it right. How can i get a more consistent CSN link acting only to the right configuration.

[TDK]

> How can i get a more consistent CSN link acting only to the right configuration.

CSN should be configured as a GPIO output pin and toggled manually before and after each transfer.

You appear to be toggling it with HAL_GPIO_WritePin, but not sure if you're initialized it correctly as you didn't include MX_GPIO_Init.

[malehakim]

this is how am initializing the GPIO ports

static void MX_GPIO_Init(void)
{
 
	GPIO_InitTypeDef GPIO_InitStruct;
	/* GPIO Ports Clock Enable */
	__HAL_RCC_GPIOA_CLK_ENABLE();
 
	GPIO_InitStruct.Pin = GPIO_PIN_4;
	GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
	GPIO_InitStruct.Pull = GPIO_NOPULL;
	GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
	HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
 
}

But still getting the glitch on the CSN line thats messing up all the data. It seems to happen when the clock is going down and MOSI is going low.....although this happens sometimes. Gash, thisz so frustrating. What on earth am i missing.

[TDK]

Should work. Remove the SPI part and just toggle PA4 until you get it working correctly. Double check connections. Make sure nothing else is competing for PA4.

[waclawek.jan]

either incorrectly initialized pin (read out and check the relevant GPIO registers content), incorrectly connected (bad solder joint), or if it is a board with more circuitry on it, it conflicts with some other output.

JW