CONFIG_UART_ASYNC_API -> uart_tx() fails when call from K_THREAD

RE: CONFIG_UART_ASYNC_API -> uart_tx() fails when call from K_THREAD

Hakon — Fri, 16 Jul 2021 13:00:13 GMT

[quote user="RAlexeev"]So, do I have 4 options to define a buffer variable for uart_tx() function, which are listed below?[/quote]

Yes, all of these options are viable I believe.

RE: CONFIG_UART_ASYNC_API -> uart_tx() fails when call from K_THREAD

RAlexeev — Mon, 12 Jul 2021 00:28:14 GMT

Hi, Hakon! Thank you for the answer! It seems that I faced about the same problem, using uart_tx() function. After making a message variable as static the UART transmission started to work properly for me also. I had something like the code below. And UART (uart_tx()) sent corrupted data to me until I made a variable message as static.

#include <zephyr.h>
#include <device.h>
#include <devicetree.h>
#include <drivers/uart.h>

#include <logging/log.h>
#define LOG_MODULE_NAME main
LOG_MODULE_REGISTER(LOG_MODULE_NAME, LOG_LEVEL_DBG);

static const struct device *uart_dev;

static void uart_cb(const struct device *dev, struct uart_event *evt, void *user_data)
{
    if (evt->type == UART_TX_DONE) {
        LOG_DBG("UART_TX_DONE: TX sent %d bytes", evt->data.tx.len);
    }
}

void main(void)
{
    int err;
    static uint8_t message[] = "Hello World!\r\n";
    const struct uart_config uart_cfg = {
        .baudrate = 115200,
        .parity = UART_CFG_PARITY_NONE,
        .stop_bits = UART_CFG_STOP_BITS_1,
        .data_bits = UART_CFG_DATA_BITS_8,
        .flow_ctrl = UART_CFG_FLOW_CTRL_NONE
    };

    uart_dev = device_get_binding(DT_LABEL(DT_NODELABEL(uart0)));

    if (uart_dev == NULL) {
        LOG_ERR("Failed to get UART device");
    }

    if (uart_configure(uart_dev, &uart_cfg) != 0) {
        LOG_ERR("Failed to configure UART");
    }

    err = uart_callback_set(uart_dev, uart_cb, NULL);
    if (err < 0) {
        LOG_DBG("Cannot set UART callback (err %d)", err);
    }

    err = uart_tx(uart_dev, message, sizeof(message), SYS_FOREVER_MS);
    if (err < 0) {
        LOG_ERR("Cannot send data over UART (err %d)", err);
    } else {
        LOG_DBG("Sent data");
    }
}

So, do I have 4 options to define a buffer variable for uart_tx() function, which are listed below?

make it static inside the function and not const (as it is implemented in this example https://github.com/nrfconnect/sdk-nrf/blob/v1.6.0/samples/edge_impulse/data_forwarder/src/main.c#L82)
make it global and not const
make it not static inside the function and not const, but wait until the end of transmission, using a semaphore, for example (as it is implemented in this example https://github.com/zephyrproject-rtos/zephyr/blob/zephyr-v2.6.0/tests/drivers/uart/uart_async_api/src/test_uart_async.c#L71)
allocate a buffer variable on the heap and release it in a callback function (as it is implemented in this example https://github.com/nrfconnect/sdk-nrf/blob/v1.6.0/applications/serial_lte_modem/src/slm_at_host.c#L86)

RE: CONFIG_UART_ASYNC_API -> uart_tx() fails when call from K_THREAD

Hakon — Tue, 06 Jul 2021 14:57:02 GMT

[quote user="SoerenBirth"]May you can explain it to me?![/quote]

The array gets erased from the stack when it exits the scope, unless it is declared static. So if uart_tx is called asynchronously, then the data that was provided to uart_tx could be erased already when the uart is trying to process the data that was provided.

RE: CONFIG_UART_ASYNC_API -> uart_tx() fails when call from K_THREAD

SoerenBirth — Fri, 02 Jul 2021 12:06:11 GMT

No, sorry.

I went on developing.

Making the message "static" fixed the problem. May you can explain it to me?!

This short message/ variable should not provoke a stack overflow.

I ran into similar problems as i was using UDP packets. Local variables tend to be unstable? Making them static fixed it again.

RE: CONFIG_UART_ASYNC_API -> uart_tx() fails when call from K_THREAD

Hakon — Fri, 02 Jul 2021 11:58:33 GMT

Hello,

would it be possible to provide the full code and project files, so I can have a closer look?