Receiving data from UART via a peripheral device

[Thomas]

Hi

I am working with a Nordic nrf52840dk using segge and sdk 16.

I am using the nordic UART example in examples/peripheral/uart.

The issue I am having is that my data being sent to this device can not be read from the nordic board.

Below is an example of the code going into my Putty terminal from my UART peripheral device.

1,1183,1,1169
1,1183,1,1169
1,1183,1,1169
1,1183,1,1169
1,1183,1,1169
1,1183,1,1169

This device has 4 wire connections RX,TX,CTS and RTS. My connections are listed below:

Note this is the default.

#define RX_PIN_NUMBER  8
#define TX_PIN_NUMBER  6
#define CTS_PIN_NUMBER 7
#define RTS_PIN_NUMBER 5

The first thing i tried was running the code with no change to see if app_uart_get(&cr) would pull this data. Unfortunately it did not. It does however, pull data that i type into the terminal.

What I want to do is to take this data from the UART(Sensor data) and store it as a variable for handling later on.

I which to know how I can pull this data from the serial connection.

Side note when the device (UART) is plugged in printing from putty does not run. If I unplug the device then printing works fine.  Below is my main code (from example).

int main(void)
{
    uint32_t err_code;

    bsp_board_init(BSP_INIT_LEDS);

    const app_uart_comm_params_t comm_params =
      {
          RX_PIN_NUMBER,
          TX_PIN_NUMBER,
          RTS_PIN_NUMBER,
          CTS_PIN_NUMBER,
          UART_HWFC,
          false,
#if defined (UARTE_PRESENT)
          NRF_UARTE_BAUDRATE_115200
#else
          NRF_UARTE_BAUDRATE_115200
#endif
/*
#if defined (UART_PRESENT)
          NRF_UART_BAUDRATE_115200
#else
          NRF_UARTE_BAUDRATE_115200
#endif
*/
      };

    APP_UART_FIFO_INIT(&comm_params,
                         UART_RX_BUF_SIZE,
                         UART_TX_BUF_SIZE,
                         uart_error_handle,
                         APP_IRQ_PRIORITY_HIGH,
                         //APP_IRQ_PRIORITY_LOWEST,
                         err_code);

    APP_ERROR_CHECK(err_code);

#ifndef ENABLE_LOOPBACK_TEST
    printf("\r\nUART example started.\r\n");

    while (true)
    {
        uint8_t cr;
        while (app_uart_get(&cr) != NRF_SUCCESS);
        while (app_uart_put(cr) != NRF_SUCCESS);

        if (cr == 'q' || cr == 'Q')
        {
            printf(" \r\nExit!\r\n");

            while (true)
            {
                // Do nothing.
            }
        }
    }
#else

    // This part of the example is just for testing the loopback .
    while (true)
    {
        uart_loopback_test();
    }
#endif
}

[Einar Thorsrud]

Hi,

It is not entirely clear to me, but the serial terminal on the PC is via the onboard debugger, right (USB connector on the left of the board)? If you are using that (or have the debugger enabled in general so that IF OFF is not asserted, then you should use different pins for the external UART device. In other words, connect the UART pins between the nRF and another device to some available GPIO pins, and update the pin number defines.

[Thomas]

Thanks for your response, I am using the onboard usb connector (the one in the top-middle of the board). This is where my putty serial terminal connects to. Jlink CDC UART PORT(COM5)

I have tried redefining the pinouts to:

#define RX_PIN_NUMBER  NRF_GPIO_PIN_MAP(0,3)//8
#define TX_PIN_NUMBER  NRF_GPIO_PIN_MAP(0,28)//6
#define CTS_PIN_NUMBER NRF_GPIO_PIN_MAP(0,4)//7
#define RTS_PIN_NUMBER NRF_GPIO_PIN_MAP(0,29)//5

I have then connected my device to those pinout.

However, I now no longer see that information (from the uart device) to putty, nor can I use a printf command and see the result.

When I  run this through the dubugger after running the APP_UART_FIFO_INIT and checking the error code it goes to NRF_BREAKPOINT_COND;

I then get this in the call stack area of the debugger.

What other details do you need to help resolve this issue?

[Einar Thorsrud]

I cannot say without knowing more. Can you share your code? At least the UART related? What state is the device in when it does not reach your breakpoint? have you tried stepping (will not work well with the SoftDevice enabled).

[Thomas]

I have tried stepping through the code and it holds on:

while (app_uart_get(&cr) != NRF_SUCCESS);

My main code is:

/**
 * Copyright (c) 2014 - 2019, Nordic Semiconductor ASA
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form, except as embedded into a Nordic
 *    Semiconductor ASA integrated circuit in a product or a software update for
 *    such product, must reproduce the above copyright notice, this list of
 *    conditions and the following disclaimer in the documentation and/or other
 *    materials provided with the distribution.
 *
 * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
 *    contributors may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 *
 * 4. This software, with or without modification, must only be used with a
 *    Nordic Semiconductor ASA integrated circuit.
 *
 * 5. Any software provided in binary form under this license must not be reverse
 *    engineered, decompiled, modified and/or disassembled.
 *
 * THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */
/** @file
 * @defgroup uart_example_main main.c
 * @{
 * @ingroup uart_example
 * @brief UART Example Application main file.
 *
 * This file contains the source code for a sample application using UART.
 *
 */

#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include "app_uart.h"
#include "app_error.h"
#include "nrf_delay.h"
#include "nrf.h"
#include "bsp.h"
#if defined (UART_PRESENT)
#include "nrf_uart.h"
#endif
#if defined (UARTE_PRESENT)
#include "nrf_uarte.h"
#endif


//#define ENABLE_LOOPBACK_TEST  /**< if defined, then this example will be a loopback test, which means that TX should be connected to RX to get data loopback. */

#define MAX_TEST_DATA_BYTES     (15U)                /**< max number of test bytes to be used for tx and rx. */
#define UART_TX_BUF_SIZE 256                         /**< UART TX buffer size. 256*/
#define UART_RX_BUF_SIZE 256                         /**< UART RX buffer size. 256*/

void uart_error_handle(app_uart_evt_t * p_event)
{
    if (p_event->evt_type == APP_UART_COMMUNICATION_ERROR)
    {
        APP_ERROR_HANDLER(p_event->data.error_communication);
    }
    else if (p_event->evt_type == APP_UART_FIFO_ERROR)
    {
        APP_ERROR_HANDLER(p_event->data.error_code);
    }
}


#ifdef ENABLE_LOOPBACK_TEST
/* Use flow control in loopback test. */
#define UART_HWFC APP_UART_FLOW_CONTROL_ENABLED

/** @brief Function for setting the @ref ERROR_PIN high, and then enter an infinite loop.
 */
static void show_error(void)
{

    bsp_board_leds_on();
    while (true)
    {
        // Do nothing.
    }
}


/** @brief Function for testing UART loop back.
 *  @details Transmitts one character at a time to check if the data received from the loopback is same as the transmitted data.
 *  @note  @ref TX_PIN_NUMBER must be connected to @ref RX_PIN_NUMBER)
 */
static void uart_loopback_test()
{
    uint8_t * tx_data = (uint8_t *)("\r\nLOOPBACK_TEST\r\n");
    uint8_t   rx_data;

    // Start sending one byte and see if you get the same
    for (uint32_t i = 0; i < MAX_TEST_DATA_BYTES; i++)
    {
        uint32_t err_code;
        while (app_uart_put(tx_data[i]) != NRF_SUCCESS);

        nrf_delay_ms(10);
        err_code = app_uart_get(&rx_data);

        if ((rx_data != tx_data[i]) || (err_code != NRF_SUCCESS))
        {
            show_error();
        }
    }
    return;
}
#else
/* When UART is used for communication with the host do not use flow control.*/
#define UART_HWFC APP_UART_FLOW_CONTROL_DISABLED
#endif


/**
 * @brief Function for main application entry.
 */
int main(void)
{
    uint32_t err_code;

    bsp_board_init(BSP_INIT_LEDS);

    const app_uart_comm_params_t comm_params =
      {
          RX_PIN_NUMBER,
          TX_PIN_NUMBER,
          RTS_PIN_NUMBER,
          CTS_PIN_NUMBER,
          UART_HWFC,
          false,
#if defined (UARTE_PRESENT)
          NRF_UARTE_BAUDRATE_115200
#else
          NRF_UARTE_BAUDRATE_115200
#endif
/*
#if defined (UART_PRESENT)
          NRF_UART_BAUDRATE_115200
#else
          NRF_UARTE_BAUDRATE_115200
#endif
*/
      };

    APP_UART_FIFO_INIT(&comm_params,
                         UART_RX_BUF_SIZE,
                         UART_TX_BUF_SIZE,
                         uart_error_handle,
                         APP_IRQ_PRIORITY_LOWEST,
                         err_code);

    APP_ERROR_CHECK(err_code);

#ifndef ENABLE_LOOPBACK_TEST
    //printf("\r\nUART example started.\r\n");

    while (true)
    {
        uint8_t cr;
        while (app_uart_get(&cr) != NRF_SUCCESS);
        while (app_uart_put(cr)  != NRF_SUCCESS);
        if (cr == 't' || cr == 't')
        {
            printf("\r\n Test passed\r\n");
        }
        if (cr == 'q' || cr == 'Q')
        {
            printf(" \r\nExit!\r\n");

            while (true)
            {
                // Do nothing.
            }
        }
    }
#else

    // This part of the example is just for testing the loopback .
    while (true)
    {
        uart_loopback_test();
    }
#endif
}


/** @} */

I cant share the config code its too large.

Using sdk 16 NRF52840 pca10056.

Also my peripheral device posts data once per second to the Nordic board.

Below is showing my connection setup (physically).

[Einar Thorsrud]

Ah, yes. I forgot that you were using the UART loopback example. It should be OK, but all this printfs will transmit data to the sensor, then. How does it handle it? I don't know what it does with it (if any), but if it causes problems you should probably remove the printfs and the call to app_uart_put(). Have you verified that you actually have the UART input data on the configured pin (using logic analyzer or simmilar)?

[Thomas]

I have removed all of the print statements. (Commented out)

And the app_uart_put.

This still does not work it goes to the break point once then when i run it, it does nothing.

I have not verified UART input data on the configured pin as I don't have access to a logic analyser.

But i thought given I could see data when it was connected to the putty terminal that, the data should be accessible.

[Einar Thorsrud]

Hi,

That is true. It should be OK. Just to double check, the pin definitions (RX_PIN_NUMBER, ...) you set are in <SDK>\components\boards\pca10056.h, right?

[Thomas]

Yes that is correct I have set them in pca10056.h as 

#define RX_PIN_NUMBER  NRF_GPIO_PIN_MAP(0,13)//8
#define TX_PIN_NUMBER  NRF_GPIO_PIN_MAP(0,11)//6
#define CTS_PIN_NUMBER NRF_GPIO_PIN_MAP(0,12)//7
#define RTS_PIN_NUMBER NRF_GPIO_PIN_MAP(0,10)//5
#define HWFC           true

[Thomas]

What should I do after confirming the pins are correct?

[Einar Thorsrud]

Good question. I assume the baud rate at flow-control configuration is correct for your device?

Essentially the example you are using is very simple, so it will make a 256 byte buffer, and put received UART data there. Then you pull single byts by calling app_uart_get(). That will return NRF_SUCCESS if there is data, and an error if not (typically NRF_ERROR_NOT_FOUND when there is no data in the buffer). So as long as the device sends data, you should not be stuck in this loop witing for data. Does the UART device always send data, or do you need to do something for it to send? If it always sends data regularly, then you should get some. What exact device is the other UART device?

One potential issue is if you never do anything later in the application. Do you use the data for anything? If not, the compiler may just discard it during compilation. It should not stick in the loop though, but it might be that it just looks like this if you are debugging a release build? Please make sure to debug with debug builds (without optimization) if you are not already doing so. If you use SES, just select "Debug" instead of "Release" in the build configuration drop-down menu.

[Thomas]

Note I have been able to receive the data from putty when directly write to the specified pins in my before setup. This printed the data once per second to the terminal at a baud rate of 115200. I have tried in segger with flow-control on and off. The date prints without CTS and RTS connected.

• The baud rate is the same as the peripheral device
• The debugger never seems to execute the app_uart_get line therefore, I cant see the error code
• The UART peripheral does not need a send command, just sends once per second
• The other UART device is a custom UART device which, I do not know all the technical details of unfortunately

In regard to no later application code what should I put if the device optimises not to do anything.

• At the moment I am just looking at the value within the debugger
• How do I debug without optimisation? 
• I have just been selecting debug within the toolbar

[Einar Thorsrud]

Hi Thomas,

I see. So the data should be sent. Do you use SES, or another IDE? If you use SES, you can select the debug build configuration from the dropdown before building and debugging. See here: