Use of a UART to transmit data (transmit/receive) between a board and an HyperTerminal PC application both in Polling and Interrupt modes. This example describes how to use the USART peripheral through the STM32C0xx UART HAL and LL API, the LL API being used for performance improvement.
Board: NUCLEO-C031C6
At the beginning of the main program the HAL_Init() function is called to reset all the peripherals, initialize the Flash interface and the systick. Then the SystemClock_Config() function is used to configure the system clock (SYSCLK) to run at 48 MHz for STM32C0xx Devices.
The UART peripheral configuration is ensured by the HAL_UART_Init() function. This later is calling the HAL_UART_MspInit() function which core is implementing the configuration of the needed UART resources according to the used hardware. You may update this function to change UART configuration.
Reception under IT on UART/Hyperterminal interface is then enabled using LL APIs. Each 0.5 sec, a predefined TX buffer is sent from MCU to PC reception of Data from Hyperterminal. The Asynchronous communication aspect of the UART is clearly highlighted as the data buffers transmission/reception to/from Hyperterminal are done simultaneously. Transmit function which allow transmission of a predefined data buffer in polling mode, is implemented using HAL UART API. Receive function which allow the reception of Data from Hyperterminal in IT mode, is implemented using LL USART API. A double buffer is available for received data, allowing continuous reception. Data received in Buffer A could be echoed on TX, while buffer B is used for reception. When buffer B is full, it is then echoed, while buffer A becomes active buffer for next reception, and so on.
For this example the TX buffer (aTxStartMessage) is predefined and the RX buffers (aRXBufferA and aRXBufferB) size is limited to 10 data by the mean of the RXBUFFERSIZE define in the main.c file.
Received data will be stored in the RX buffer. When RX buffer is full, RX buffer is sent back to PC and led toggles.
The Asynchronous communication aspect of the UART is clearly highlighted as the data buffers transmission/reception to/from Hyperterminal are done simultaneously.
STM32 Nucleo board’s LEDs can be used to monitor the transfer status:
The UART is configured as follows:
- BaudRate = 9600 baud
- Word Length = 8 Bits (7 data bit + 1 parity bit)
- One Stop Bit
- Odd parity
- Hardware flow control disabled (RTS and CTS signals)
- Reception and transmission are enabled in the time
When the parity is enabled, the computed parity is inserted at the MSB position of the transmitted data.
Care must be taken when using HAL_Delay(), this function provides accurate delay (in milliseconds) based on variable incremented in SysTick ISR. This implies that if HAL_Delay() is called from a peripheral ISR process, then the SysTick interrupt must have higher priority (numerically lower) than the peripheral interrupt. Otherwise the caller ISR process will be blocked. To change the SysTick interrupt priority you have to use HAL_NVIC_SetPriority() function.
The application needs to ensure that the SysTick time base is always set to 1 millisecond to have correct HAL operation.
Connectivity, UART/USART, baud rate, RS-232, HyperTerminal, full-duplex, Interrupt, Polling, Transmitter, Receiver, Asynchronous
This example runs on NUCLEO-C031C6 devices.
This example has been tested with STMicroelectronics NUCLEO-C031C6 board and can be easily tailored to any other supported device and development board.
NUCLEO-C031C6 Set-up
Example is delivered for using Virtual Com port feature of STLINK for connection between NUCLEO-C031C6 and PC, Please ensure that USART communication between the target MCU and ST-LINK MCU is properly enabled on HW board in order to support Virtual Com Port (Default HW SB configuration allows use of VCP) GPIOs connected to USART2 TX/RX (PA2 and PA3) are automatically mapped on RX and TX pins of PC UART Com port selected on PC side (please ensure VCP com port is selected).
Launch serial communication SW on PC (as HyperTerminal or TeraTerm) with proper configuration
In order to make the program work, you must do the following :