![]() ![]() I think the overhead of setting up DMA makes more sense for larger sequential transactions into (or out of) buffers, and less so for the single byte-by-byte case. Care must be taken in deciding when to enable/disable the TX complete interrupt. Based on those two events, you can decide to buffer the data (in the RX handler) and to empty the buffer (in TX complete handler). You can have 2 interrupt service routines for when a byte is received and when the transmit data register is empty. However, I think doing away with DMA and using the USART interrupts would be a better approach. That's one way to do it, I would imagine it would work. Writing into the USART data register while the TXE status bit is not set is a guaranteed way to lose information. This flag generates an interrupt if the TXEIE bit isĬan you imagine a scenario where you are writing into the data register before the previous byte has made it into the shift register? Think about the sequence of events when you receive a stream of bytes, especially when you receive the third or fourth byte, what is your transmitter doing at this point? Is its data register occupied?Īs a previous comment mentioned, you likely need a way to buffer previous byte(s) if the TXE status bit is not set. The next data can be written in the USART_DR register without overwriting the previous data.Serial Communication, SIM900, ST Nucleo F401RE. answers strange situetion with serial Antoniolinux B. The data has been moved from TDR to the shift register and the data SIM900 and AT CMGW Hamza BENDALI BRAHAM 6 years, 10 months ago.Everything about AT commands, schematics, tutorial The first thing to do is read manuals. The TXE bit is set by hardware and it indicates: Price: 20.99 Brand: SainSmart Click on LEARN, there is a lot of documents to download. The TXE bit is always cleared by a write to If((Timeout = 0)||((HAL_GetTick() - tickstart ) > Timeout))Ĭonsider the following snippet from the STM32F1 manual regarding the USART data register and its corresponding status bit 'TXE': While(_HAL_UART_GET_FLAG(huart, Flag) = RESET) com/sending-a-text-message-using-sim900-gsm-with-an-stm32-microcontroller/. To be exact, it goes inside this first if and waits for the next character to be received: /* Wait until flag is set */ Thanks so stm32 gsm at command mean stm32 - Static IP for Telit GL865 GSM. ![]() When I step into the HAL_UART_Receive function in debug mode, I see the program stuck inside static HAL_StatusTypeDef UART_WaitOnFlagUntilTimeout() function. If( HAL_UART_Receive(
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