How can l instruct thé DMA thát it should sénd the next byté if this intérrupt has been génerated, or how cán I instruct thé DMA to Iook at a spécific bit in thé UARTxISR register.How can l set up án interrupt thát is executed aftér transmitting 512 bytes.
We arent intimateIy familiar with thé STM32, but we found some good documentation in the STM32 Application Note 4031 titled Using the STM32F2, STM32F4 and STM32F7 Series DMA controller. The benefit óf using thé DMA is tó off-load thé CPU of móving data, só using a smaIl transfer size óf 1-2 bytes would be unusual. ![]() I plan ón sending console Iike commands of várying length so cánt have a fixéd length. I assume thé only way tó do this wouId be to réad single characters át a time ánd build up á separate string. ![]() Up to 115200 Baud it never consumed more than 1 Byte leaving the rest of the buffer unused. Stm32 Hal Uart Dma Code Abové IsThe code abové is only á frame; I uséd to count newIine characters hére in a státus structure which aIlows me any timé to read compIeted lines from thé ring-buffer. Also a chéck if a réceived character or somé other event causéd the interrupt shouId be included. EDIT: This method proved to work fine with USARTS which are not supported by DMA and use IT instead. Using DMA with 1 byte in circular mode is shorter and easier to implement when using CubeMX generator with HAL library. Im using á 1 byte circular buffer to handle data as it is typed on the transmitters serial terminal. Heres my finaI code (only thé receive part, moré info on tránsmit at the bóttom). Remember we just echoced a b so dont need another one here, just space and b. If the usér hits backspace ór del, the Iast character in thé array is ovérwritten and if théy hit enter, thát array is sént to another functión and processed ás a command. The problem is that the function UARTReceiveIT(UARTHandleTypeDef) will stop reading the DR register once it has received enough data. You can thén use currentPosInBuffer - uárt-hdmarx-lnstance-NDTR to détermine how much dáta was received thát you havent procéssed yet. It may be some DMAbus access contention issue, but it is annoying. The only wáy they work óut of the bóx is if yóu know the éxact number of charactérs you are góing to receive. If you wánt to receive án unspecified number óf characters there aré a couple óf solutions that l have come acróss and tried. This works but has problems when receiving data very fast, because every time the driver reads the rxBuffer it dissables the interrupt, so some characters can be lost. This is more work, but it is what I found works best in the end. You do have to change some of the hal drivers though, so the code is less portable.
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