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How To: UART Interface

Core Module has 3 UARTs you can use. The signal for each channel is named TXDx, RXDx where x is 0, 1 or 2.

Please refer to the module drawing pinout where you find the signal's positions.

References​

UART Write​

Synchronous Write​

Function twr_uart_write needs to know how many bytes to send. That’s why you need to use sizeof(uart_tx).

info

This example will write a Hello world through the UART1 with the baudrade of 115200.

There will be 8 data bits, none parity and 1 stop bit.

This writing is blocking, you will have to wait before the write is done.

Synchronous UART Write Code Example

#include <application.h>

void application_init()
{
    twr_uart_init(TWR_UART_UART1, TWR_UART_BAUDRATE_115200, TWR_UART_SETTING_8N1);
    char uart_tx[] = "Hello world\r\n";
    twr_uart_write(TWR_UART_UART1, uart_tx, strlen(uart_tx));
}

Asynchronous Write​

info

This is a little bit complicated because you need to create a FIFO structure and a FIFO buffer array. Then you initialize the FIFO and assign it to the UART.

In this example, we demonstrate just the async write.

Asynchronous UART Write Code Example

#include <application.h>

twr_fifo_t tx_fifo;
uint8_t tx_fifo_buffer[32];

void uart_handler(twr_uart_channel_t channel, twr_uart_event_t event, void *param)
{
    if (event == TWR_UART_EVENT_ASYNC_WRITE_DONE)
    {
        // here you can for example send more data
    }
}

void application_init()
{
    twr_uart_init(TWR_UART_UART1, TWR_UART_BAUDRATE_115200, TWR_UART_SETTING_8N1);
    twr_uart_set_event_handler(TWR_UART_UART1, uart_handler, NULL);

    twr_fifo_init(&tx_fifo, tx_fifo_buffer, sizeof(tx_fifo_buffer));
    // We set only TX FIFO, for RX_FIFO we pass NULL
    twr_uart_set_async_fifo(TWR_UART_UART1, &tx_fifo, NULL);

    char uart_tx[] = "Hello world\r\n";
    twr_uart_async_write(TWR_UART_UART1, uart_tx, strlen(uart_tx));
}

UART Read​

There are again two options to read received bytes. You can read data synchronously in your task, or asynchronously using callbacks.

Synchronous Read​

Synchronous UART Read Code Example

void application_task()
{
    // Define receive buffer
    uint8_t uart_rx[32];
    // Synchronous reading
    size_t number_of_rx_bytes = twr_uart_read(TWR_UART_UART1, uart_rx, sizeof(uart_rx), 500);

    char uart_tx[32];
    snprintf(uart_tx, sizeof(uart_tx), "RX bytes: %d\r\n", number_of_rx_bytes);
    twr_uart_write(TWR_UART_UART1, uart_tx, strlen(uart_tx));

    twr_scheduler_plan_current_now();
}

Asynchronous Read​

info

This example does asynchronous send and receives of data on TWR_UART_UART1 with the baudrade of 115200.

There will be 8 data bits, none parity and 1 stop bit.

caution

This example is not low power. If you start UART reading with twr_uart_async_read_start function the Core Module will not go to sleep until you call the twr_uart_async_read_stop.

Asynchronous UART Read Code Example

#include <application.h>

twr_fifo_t tx_fifo;
twr_fifo_t rx_fifo;
uint8_t tx_fifo_buffer[64];
uint8_t rx_fifo_buffer[64];

void uart_handler(twr_uart_channel_t channel, twr_uart_event_t event, void *param)
{
    uint8_t rx_data[32];

    if (event == TWR_UART_EVENT_ASYNC_WRITE_DONE)
    {
        // here you can for example send more data
    }
    if (event == TWR_UART_EVENT_ASYNC_READ_DATA)
    {
        // Read data from FIFO by a single byte as you receive it
        size_t number_of_rx_bytes = twr_uart_async_read(TWR_UART_UART1, rx_data, sizeof(rx_data));
        char uart_tx[32];
        snprintf(uart_tx, sizeof(uart_tx), "RX: %d\r\n", number_of_rx_bytes);
        twr_uart_async_write(TWR_UART_UART1, uart_tx, strlen(uart_tx));
    }
    if (event == TWR_UART_EVENT_ASYNC_READ_TIMEOUT)
    {
        // No data received during set timeout period
        char uart_tx[] = "Timeout\r\n";
        twr_uart_async_write(TWR_UART_UART1, uart_tx, strlen(uart_tx));
        // You can also read received bytes here instead of TWR_UART_EVENT_ASYNC_READ_DATA
    }
}

void application_init()
{
    twr_uart_init(TWR_UART_UART1, TWR_UART_BAUDRATE_115200, TWR_UART_SETTING_8N1);
    twr_uart_set_event_handler(TWR_UART_UART1, uart_handler, NULL);

    twr_fifo_init(&tx_fifo, tx_fifo_buffer, sizeof(tx_fifo_buffer));
    twr_fifo_init(&rx_fifo, rx_fifo_buffer, sizeof(rx_fifo_buffer));

    twr_uart_set_async_fifo(TWR_UART_UART1, &tx_fifo, &rx_fifo);

    twr_uart_async_read_start(TWR_UART_UART1, 500);

    char uart_tx[] = "Hello world\r\n";
    twr_uart_async_write(TWR_UART_UART1, uart_tx, strlen(uart_tx));
}