Core2ForAWS_Port_C_UART_Send

int Core2ForAWS_Port_C_UART_Send(const char *message, size_t len);

Sends a specified length of a user defined message over UART2.

This is a helper function to simplify transmitting data over UART using the UART channel 2. This function does not return until all bytes are either transferred from the ring buffer to the hardware FIFO buffer, or already sent.

For more information about UART communications on the Core2 for AWS IoT EduKit using the ESP32, visit Espressif's official documentation.

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]	message	A pointer to the message to be transmitted over UART2.
[in]	len	The size of the message that you want to transmit.

Returns

The 0 or greater number of bytes pushed to the TX FIFO. A return value -1 represents an error in one of the provided parameters.