HAL_UART_Transmit_DMA(), only works with inline defined string and fails with globaly defined array

[zhausq]

why does this work:

HAL_UART_Transmit_DMA(&huart6, (uint8_t *)"stm32\n", 6); // works and sends data

and this doesnt:

ALIGN_32BYTES (uint8_t aTxBuffer[]) = "stm32\n";

HAL_UART_Transmit_DMA(&huart6, (uint8_t *)aTxBuffer, 6) // doesnt send any data

what am i missing?

[Piranha]

Most likely aTxBuffer is located in DTCM, to which only the MDMA has access in H7 series. Take a look at AN4891 figure 1.

[hs2]

DMA buffers must be located in (the appropriate) RAM. Fixed strings or other constant data are usually stored in ROM (flash).

You should verify/ensure that the data is provided on stack / RAM.

[zhausq · Accepted solution]

solved! appreciate the quick responses, thank you!

for anyone whose reading this and having the same issue: this is what you're looking for https://community.st.com/s/article/FAQ-DMA-is-not-working-on-STM32H7-devices

[Amel NASRI]

Glad to know that your question is answered. Please mark the article as helpful in this case.

Thanks

Amel