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 SDK Module
• GitHub Repository Example

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));
}