Chapter 2. API Reference
Application Examples
The table below describes the code examples available in the directory peripherals/uart/.
Code Example Description
peripherals/uart/uart_echo Configuring UART settings, installing the UART driver, and read-
ing/writing over the UART1 interface.
peripherals/uart/uart_events Reporting various communication events, using pattern detection inter-
rupts.
peripherals/uart/uart_async_rxtxtasks Transmitting and receiving data in two separate FreeRTOS tasks over the
same UART.
peripherals/uart/uart_select Using synchronous I/O multiplexing for UART file descriptors.
peripherals/uart/uart_echo_rs485 Setting up UART driver to communicate over RS485 interface in half-
duplex mode. This example is similar to peripherals/uart/uart_echo but
allows communication through an RS485 interface chip connected to
ESP32-S2 pins.
peripherals/uart/nmea0183_parser Obtaining GPS information by parsing NMEA0183 statements received
from GPS via the UART peripheral.
API Reference
Header File
• components/driver/include/driver/uart.h
Functions
esp_err_t uart_driver_install(uart_port_t uart_num, int rx_buffer_size, int tx_buffer_size, int
queue_size, QueueHandle_t *uart_queue, int intr_alloc_flags)
Install UART driver and set the UART to the default configuration.
UART ISR handler will be attached to the same CPU core that this function is running on.
Note Rx_buffer_size should be greater than UART_FIFO_LEN. Tx_buffer_size should be either zero or
greater than UART_FIFO_LEN.
Return
• ESP_OK Success
• ESP_FAIL Parameter error
Parameters
• uart_num: UART port number, the max port number is (UART_NUM_MAX -1).
• rx_buffer_size: UART RX ring buffer size.
• tx_buffer_size: UART TX ring buffer size. If set to zero, driver will not use TX buffer, TX
function will block task until all data have been sent out.
• queue_size: UART event queue size/depth.
• uart_queue: UART event queue handle (out param). On success, a new queue handle is written
here to provide access to UART events. If set to NULL, driver will not use an event queue.
• intr_alloc_flags: Flags used to allocate the interrupt. One or multiple
(ORred) ESP_INTR_FLAG_* values. See esp_intr_alloc.h for more info. Do not set
ESP_INTR_FLAG_IRAM here (the driver’s ISR handler is not located in IRAM)
esp_err_t uart_driver_delete(uart_port_t uart_num)
Uninstall UART driver.
Return
• ESP_OK Success
• ESP_FAIL Parameter error
Parameters
• uart_num: UART port number, the max port number is (UART_NUM_MAX -1).
bool uart_is_driver_installed(uart_port_t uart_num)
Checks whether the driver is installed or not.
Espressif Systems 464
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