Posted on June 20, 2018 at 11:44maybe change your approach a little.
I track the DMA buffer size, do you know the incoming packet length ?
with this code style, I can peek at the receive buffer before I receive it.
lets say you are in the mS systick process, you can call these ;
char readableU1(void) { // incoming bytes ptr is calculated from the DMA pointer
U1RxBufferPtrIN = U1RxBufSize - huart1.hdmarx->Instance->CNDTR;
return (U1RxBufferPtrIN - U1RxBufferPtrOUT) & (U1RxBufSize-1); // bufSize must be 2^n // unread buffer length
}
char getc1(void) {
char Rxbyte = Usart1RxDMABuffer[U1RxBufferPtrOUT++];
if (U1RxBufferPtrOUT >= U1RxBufSize) U1RxBufferPtrOUT = 0;
return Rxbyte;
}
char peekRxU1(int offset) { // offset of zero returns the next byte to be read
int relativePtr = (U1RxBufferPtrOUT+ offset) & (U1RxBufSize-1); // bufSize must be 2^n
char PeekRx= Usart1RxDMABuffer[relativePtr ]; // just looking Don't increment pointer
return PeekRx;
}
you know the current output pointer U1RxBufferPtrOUT
and you can read the current DMA input pointer U1RxBufferPtrIN
lets say your frame is 3- 10 bytes long
currentUnreadBufferSize = (U1RxBufferPtrIN - U1RxBufferPtrOUT) & (U1RxBufSize-1); // bufSize must be 2^n
