Using custom RX/TX UART pins on nrf51822

Question

Hi, 
 I have developed an application on an nrf51dk, with SDK12.3 (as it was the latest that I could make it work with). It is running fine on the DK, but when moving to the custom pcb i ran into a few problems, one of them being that the DK uses pins TX=P0.09 and RX=P0.11 and our custom board uses TX=P0.17 and RX=P0.18. 
 Coincidentally, my code is still monitoring the buttons on the DK board, and because of this, and although the UART is not working on my custom board, while debugging it I was seeing logs for bsp_event_t BSP_EVENT_KEY_0, which is actually pin P0.17 (the pin my board uses for UART RX), so my guess is that UART activity on my custom board is being interpreted as a button event. 
 So, the next step was to disable the call to bsp_init(), in the hopes I would be disabling button monitoring, but that is still not enough to make the UART work. 
 Question: what are the steps to allow using custom pins for UART on the nrf51822, under SDK12.3? 
 
 Best regards, 
 Ricardo

Jørgen Holmefjord · Accepted Answer

I tested your code in the UART example in SDK 12.3.0: Fullscreen main.c Download /** * Copyright (c) 2014 - 2017, 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 #include #include #include "app_uart.h" #include "app_error.h" #include "nrf_delay.h" #include "nrf.h" #include "bsp.h" //#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. */ #define UART_RX_BUF_SIZE 256 /**< UART RX buffer size. */ 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); } } void uart_init(void) { uint32_t err_code; const app_uart_comm_params_t comm_params = { //RX_PIN_NUMBER, TX_PIN_NUMBER, 18,17, RTS_PIN_NUMBER, CTS_PIN_NUMBER, APP_UART_FLOW_CONTROL_DISABLED, false, UART_BAUDRATE_BAUDRATE_Baud9600 }; 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); } /** * @brief Function for main application entry. */ int main(void) { bsp_board_leds_init(); uart_init(); printf(" Start: "); 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(" Exit! "); while (true) { // Do nothing. } } } } /** @} */ I tested this on a nRF51 DK by connecting P0.17 to P0.09 and P0.18 to P0.11. It seems to work fine. Can you test this on your board?

Using custom RX/TX UART pins on nrf51822

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