SPI troubles

[Stoufer]

Hi - I have a new board with very minimal parts other than a STM32L451VET6 micro and a SPI LCD.

I have implemented SPI and the micro is sending data when I single step the program. When I just let it run it Sends exactly three and one half bytes... every time. I am using the following code :

HAL_GPIO_WritePin(DISP_CS_GPIO_Port, DISP_CS_Pin, GPIO_PIN_RESET); // set CS low

HAL_SPI_Transmit(&hspi1, (uint8_t *)&spi_init_cmds_new, 18, 100); // write init data to display

HAL_GPIO_WritePin(DISP_CS_GPIO_Port, DISP_CS_Pin, GPIO_PIN_SET); // set CS high

it seems like some sort of timing issue because it will single step and send two bytes at a time with CS toggling between them as it should. It setup for Master transmit only since my display doesn't have a read function.

I set the internal clock (MSI RC ) to 8000 with a SPI prescaler of 128  for a baud of 62.5kbits. Here is the SPI config : 

for testing I added a HAL_Delay(500); line right after the SPI write and when single stepping it locked up on that line...

Any ideas are appreciated !!

Thanks

[Pavel A.]

> HAL_GPIO_WritePin(DISP_CS_GPIO_Port, DISP_CS_Pin, GPIO_PIN_RESET); // set CS low

Why is this? You've configured hardware NSS output on PB0. Is DISP_CS defined as PB0?

[TDK · Accepted solution]

You could try initializing it in two-line mode and leave MISO disconnected. I don't think there are bugs/issues in master transmit-only like there are for receive-only, but there could be.

Would be nice to see more of the relevant code and traces of the signals you're seeing, make sure word size is configured correctly.

[Stoufer]

yes 

[Stoufer]

Its fixed! I had tried using Master Full-Duplex yesterday. But before I was using NSS hardware output.

So ... using NSS hardware out, and setting it for Master full-duplex is now working.

Thanks Guys !!