Core2ForAWS_Port_C_UART_Begin

esp_err_t Core2ForAWS_Port_C_UART_Begin(uint32_t baud);

Configures the UART interface at the specified baud rate.

This is a helper function to simplify building applications with UART. It preconfigures the UART communications with word length of 8 bits, no parity bit, 1 bit for the number of stop bits, and hardware flow control disabled. It sets the baud rate to the user defined value and starts reading from the UART channel 2 and storing data into the ring buffer of length UART_RX_BUF_SIZE.

Usage of the UART convenience methods provided in this BSP aims to simplify development at the expense of compatibility and performance. The configuration above may not be suitable for your application or attached peripheral. For more information about UART communications on the Core2 for AWS IoT EduKit using the ESP32 and how to create your own configuration, visit Espressif's official documentation.

Note

The ESP32 is a 3.3v device and requires 3.3v on the UART TX/RX lines. Higher voltages requires the use of a level shifter.

The example below sets the PORT_C_UART_TX_PIN (GPIO 14) pin mode to UART transmit, which will also set PORT_C_UART_RX_PIN (GPIO 13) to UART receiver, and sets the UART baud rate to 115200. It then starts two FreeRTOS tasks — one that transmits "Hello from AWS IoT EduKit" every two seconds and the other receives the message. The receiver task outputs the number of bytes read from the buffer, the number of bytes that remains unread in the ring buffer, and the message.

To receive the messages transmitted on the same device, run a female-female jumper wire from Port C's TX pin to PORT C's RX pin.

Example:

#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/uart.h"
#include "driver/gpio.h"
#include "esp_log.h"
 
#include "core2forAWS.h"
 
static const char *TAG = "UART_DEMO";
 
static void uart_tx_task(void *arg){
    while (1) {
        const char *message = "Hello from AWS IoT EduKit";
        size_t message_len = strlen(message) + 1;
        Core2ForAWS_Port_C_UART_Send(message, message_len);
        vTaskDelay(pdMS_TO_TICKS(2000));
    }
}
 
static void uart_rx_task(void *arg){
    int rxBytes;
    uint8_t *data = heap_caps_malloc(UART_RX_BUF_SIZE, MALLOC_CAP_SPIRAM); // Allocate space for message in external RAM
    while (1) {
        rxBytes = Core2ForAWS_Port_C_UART_Receive(data);
        if (rxBytes > 0) {
            ESP_LOGI(TAG, "Read %d bytes from UART. Received: '%s'", rxBytes, data);
        }
        vTaskDelay(pdMS_TO_TICKS(100)); // Read more frequently than transmit to ensure the messages are not erased from buffer.
    }
    free(data); // Free memory from external RAM
}
 
void app_main(void){
    Core2ForAWS_Init();
    esp_err_t err = Core2ForAWS_Port_PinMode(PORT_C_UART_TX_PIN, UART);
    if (err == ESP_OK){
        Core2ForAWS_Port_C_UART_Begin(115200);
        xTaskCreate(uart_rx_task, "uart_rx", 1024*2, NULL, configMAX_PRIORITIES, NULL);
        xTaskCreate(uart_tx_task, "uart_tx", 1024*2, NULL, configMAX_PRIORITIES-1, NULL);
    }
}

Parameters

[in]

baud

The baud rate (bits per second) of the UART2 channel.

Returns

esp_err_t. 0 or ESP_OK if successful.