Data transmit by UARD (DMA) with junk character

[jlecl.1]

Dear eveyone,

I' little confuse..

I'm trying to send dat over uart from a nucleo board (F103 + FDTI). If a use "normal"method, it's work great.

I mean, i receive "1234567890" WITH a new line.

uint8_t start [20]= "1234567890 \n\r";
HAL_UART_Transmit(&huart1, start, sizeof(start),10);

But when i use DMA

uint8_t start [20]= "1234567890 \n\r";
HAL_UART_Transmit_DMA(&huart1, start, sizeof(start));

I get a lot of<NULL> character before data...

Maybe a need to reinit the buffer DMA ?

if you have an idea...

[jlecl.1]

error : the junk charater appears after the \n\r...

[Tesla DeLorean · Accepted solution]

Use strlen() not sizeof() for strings.

HAL DMA functions return IMMEDIATELY, make sure that the variable remains in SCOPE for the entirety of the transfer, and make sure not to start new transfers until the prior one has completed.

[jlecl.1]

recess... thanks a lot !

[Tesla DeLorean]

1. uint8_t start[]= "1234567890 \n\r";
2. HAL_UART_Transmit_DMA(&huart1, start, strlen(start));