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This application note explains how to use the STM32H7 UART interfaces in the FreeRTOS demo application.
1. Understanding UART Interfaces
1.1. FreeRTOS UART Implementation
The FreeRTOS BSP provides a device driver for the UART interfaces. The driver is configured (enabled / disabled) at the BSP build time, using the HAL_UART_MODULE_ENABLED configuration option, defined in the stm32h7xx_hal_conf.h file.
1.2. FreeRTOS UART C-Binding API
The UART driver implements the following C-binding API:
Function | Description | Comments |
uart_handler * uart_init(uint32_t port, uint32_t rx_mode, uint32_t tx_mode)
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| Initialize a specified UART interface | port is the UART interface (1 to 8 corresponding to the number of the UART interfaces; rx_mode defines how receivers will be performed, possible values are UART_POLLING, UART_INTERRUPT, UART_DMA; tx_mode defines how transmit will be performed; possible values are UART_POLLING, UART_INTERRUPT, UART_DMA; returns the UART interface handle or 0 in case of error
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int uart_read(uart_handler * huart, uint8_t * pdata, uint16_t size, uint32_t timeout)
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| Receive an amount of data | huart is the UART interface handle; pdata is the pointer to data buffer; size is the amount of data to be received; timeout is the amount of ticks for timeout in polling mode; returns a number of received bytes or a negative error code
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int uart_write(uart_handler * huart, uint8_t * pdata, uint16_t size, uint32_t timeout)
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| Send an amount of data | huart is the UART interface handle; pdata is the pointer to data buffer; size is the amount of data to be sent; timeout is the amount of ticks for timeout in polling mode; returns a number of transmitted bytes or a negative error code
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HAL_StatusTypeDef uart_deinit(uart_handler * huart)
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| De-Initialize the UART interface | huart is the UART interface handle; returns the status of operation
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1.3. UART CLI Command
The FreeRTOS application implements the following UART related CLI command:
Command | Description | Comments |
uart_test <port> <baudrate> <count>
| Read data from the specified UART interface at the baudrate rate and send it back to the same UART interface. The command exits if the count bytes have been received or the special charcter OEF has been detected. | |
2. Validating UART Operation
Use the following step-wise procedure to validate the UART operation:
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