first commit
This commit is contained in:
David R.
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# The following lines of boilerplate have to be in your project's CMakeLists
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# in this exact order for cmake to work correctly
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cmake_minimum_required(VERSION 3.16)
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include($ENV{IDF_PATH}/tools/cmake/project.cmake)
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# "Trim" the build. Include the minimal set of components, main, and anything it depends on.
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idf_build_set_property(MINIMAL_BUILD ON)
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project(echo_rs485)
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| Supported Targets | ESP32 | ESP32-C2 | ESP32-C3 | ESP32-C5 | ESP32-C6 | ESP32-C61 | ESP32-H2 | ESP32-H21 | ESP32-H4 | ESP32-P4 | ESP32-S2 | ESP32-S3 |
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| ----------------- | ----- | -------- | -------- | -------- | -------- | --------- | -------- | --------- | -------- | -------- | -------- | -------- |
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# UART RS485 Echo Example
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(See the README.md file in the upper level 'examples' directory for more information about examples.)
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This is an example which echoes any data it receives on UART port back to the sender in the RS485 network.
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It uses ESP-IDF UART software driver in RS485 half duplex transmission mode and requires external connection of bus drivers.
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The approach demonstrated in this example can be used in user application to transmit/receive data in RS485 networks.
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## How to use example
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### Hardware Required
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PC + USB Serial adapter connected to USB port + RS485 line drivers + Espressif development board.
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The MAX483 line driver is used for example below but other similar chips can be used as well.
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#### RS485 example connection circuit schematic:
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```
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VCC ---------------+ +--------------- VCC
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| |
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+-------x-------+ +-------x-------+
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RXD <------| RO | | RO|-----> RXD
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| B|---------------|B |
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TXD ------>| DI MAX483 | \ / | MAX483 DI|<----- TXD
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ESP32 BOARD | | RS-485 side | | SERIAL ADAPTER SIDE
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RTS --+--->| DE | / \ | DE|---+
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| | A|---------------|A | |
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+----| /RE | | /RE|---+-- RTS
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+-------x-------+ +-------x-------+
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--- ---
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```
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#### Connect an external RS485 serial interface to an ESP32 board
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Connect a USB-to-RS485 adapter to a computer, then connect the adapter's A/B output lines with the corresponding A/B output lines of the RS485 line driver connected to the ESP32 chip (see figure above).
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```
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------------------------------------------------------------------------------------------------------------------------------
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| UART Interface | #define | Default pin for ESP32 | Default pins for others | External RS485 Driver Pin |
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| ----------------------|--------------------|-----------------------|---------------------------|---------------------------|
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| Transmit Data (TxD) | CONFIG_MB_UART_TXD | GPIO23 | GPIO9 | DI |
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| Receive Data (RxD) | CONFIG_MB_UART_RXD | GPIO22 | GPIO8 | RO |
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| Request To Send (RTS) | CONFIG_MB_UART_RTS | GPIO18 | GPIO10 | ~RE/DE |
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| Ground | n/a | GND | GND | GND |
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------------------------------------------------------------------------------------------------------------------------------
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```
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Note: Each target chip has different GPIO pins available for UART connection. Please refer to UART documentation for selected target for more information.
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### Configure the project
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```
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idf.py menuconfig
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```
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### Build and Flash
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Build the project and flash it to the board, then run monitor tool to view serial output:
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```
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idf.py -p PORT flash monitor
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```
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(To exit the serial monitor, type ``Ctrl-]``.)
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See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.
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#### Setup external terminal software
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Refer to the example and set up a serial terminal program to the same settings as of UART in ESP32-WROVER-KIT board.
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Open the external serial interface in the terminal. By default if no any symbols are received, the application sends character `.` to check transmission side.
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When typing message and push send button in the terminal you should see the message `RS485 Received: [ your message ]`, where "your message" is the message you sent from terminal.
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Verify if echo indeed comes from your board by disconnecting either `TxD` or `RxD` pin. Once done there should be no any `.` displayed.
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## Example Output
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Example output of the application:
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```
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I (655020) RS485_ECHO_APP: Received 12 bytes:
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[ 0x79 0x6F 0x75 0x72 0x20 0x6D 0x65 0x73 0x73 0x61 0x67 0x65 ]
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```
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The received message is showed in hexadecimal form in the brackets.
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## Troubleshooting
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When example software does not show the `.` symbol, the issue is most likely related to connection errors of the external RS485 interface.
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Check the RS485 interface connection with the environment according to schematic above and restart the application.
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Then start terminal software and open the appropriate serial port.
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idf_component_register(SRCS "rs485_example.c"
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REQUIRES nvs_flash esp_driver_uart
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INCLUDE_DIRS ".")
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menu "Echo RS485 Example Configuration"
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orsource "$IDF_PATH/examples/common_components/env_caps/$IDF_TARGET/Kconfig.env_caps"
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config ECHO_UART_PORT_NUM
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int "UART port number"
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range 0 2 if IDF_TARGET_ESP32 || IDF_TARGET_ESP32S3
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default 2 if IDF_TARGET_ESP32 || IDF_TARGET_ESP32S3
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range 0 1
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default 1
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help
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UART communication port number for the example.
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See UART documentation for available port numbers.
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config ECHO_UART_BAUD_RATE
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int "UART communication speed"
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range 1200 115200
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default 115200
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help
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UART communication speed for Modbus example.
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config ECHO_UART_RXD
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int "UART RXD pin number"
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range ENV_GPIO_RANGE_MIN ENV_GPIO_IN_RANGE_MAX
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default 27 if IDF_TARGET_ESP32P4
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default 22 if IDF_TARGET_ESP32
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default 8 if !IDF_TARGET_ESP32
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help
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GPIO number for UART RX pin. See UART documentation for more information
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about available pin numbers for UART.
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config ECHO_UART_TXD
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int "UART TXD pin number"
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range ENV_GPIO_RANGE_MIN ENV_GPIO_OUT_RANGE_MAX
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default 26 if IDF_TARGET_ESP32P4
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default 23 if IDF_TARGET_ESP32
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default 9 if !IDF_TARGET_ESP32
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help
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GPIO number for UART TX pin. See UART documentation for more information
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about available pin numbers for UART.
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# config ECHO_UART_RTS
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# int "UART RTS pin number"
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# range ENV_GPIO_RANGE_MIN ENV_GPIO_OUT_RANGE_MAX
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# default -1 if IDF_TARGET_ESP32P4
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# default 18 if IDF_TARGET_ESP32
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# default 10 if !IDF_TARGET_ESP32
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# help
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# GPIO number for UART RTS pin. This pin is connected to
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# ~RE/DE pin of RS485 transceiver to switch direction.
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# See UART documentation for more information about available pin
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# numbers for UART.
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config ECHO_TASK_STACK_SIZE
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int "UART echo RS485 example task stack size"
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range 1024 16384
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default 3072
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help
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Defines stack size for UART echo RS485 example. Insufficient stack size can cause crash.
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endmenu
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/* Uart Events Example
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This example code is in the Public Domain (or CC0 licensed, at your option.)
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Unless required by applicable law or agreed to in writing, this
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software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
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CONDITIONS OF ANY KIND, either express or implied.
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*/
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include "freertos/FreeRTOS.h"
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#include "freertos/task.h"
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#include "esp_system.h"
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#include "nvs_flash.h"
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#include "driver/uart.h"
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#include "freertos/queue.h"
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#include "esp_log.h"
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#include "sdkconfig.h"
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/**
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* This is a example which echos any data it receives on UART back to the sender using RS485 interface in half duplex mode.
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*/
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#define TAG "RS485_ECHO_APP"
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// Note: Some pins on target chip cannot be assigned for UART communication.
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// Please refer to documentation for selected board and target to configure pins using Kconfig.
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#define ECHO_TEST_TXD (CONFIG_ECHO_UART_TXD)
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#define ECHO_TEST_RXD (CONFIG_ECHO_UART_RXD)
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// RTS for RS485 Half-Duplex Mode manages DE/~RE
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#define ECHO_TEST_RTS (UART_PIN_NO_CHANGE)
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// CTS is not used in RS485 Half-Duplex Mode
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#define ECHO_TEST_CTS (UART_PIN_NO_CHANGE)
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#define BUF_SIZE (127)
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#define BAUD_RATE (CONFIG_ECHO_UART_BAUD_RATE)
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// Read packet timeout
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#define PACKET_READ_TICS (100 / portTICK_PERIOD_MS)
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#define ECHO_TASK_STACK_SIZE (CONFIG_ECHO_TASK_STACK_SIZE)
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#define ECHO_TASK_PRIO (10)
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#define ECHO_UART_PORT (CONFIG_ECHO_UART_PORT_NUM)
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// Timeout threshold for UART = number of symbols (~10 tics) with unchanged state on receive pin
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#define ECHO_READ_TOUT (3) // 3.5T * 8 = 28 ticks, TOUT=3 -> ~24..33 ticks
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static void echo_send(const int port, const char* str, uint8_t length)
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{
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if (uart_write_bytes(port, str, length) != length) {
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ESP_LOGE(TAG, "Send data critical failure.");
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// add your code to handle sending failure here
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abort();
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}
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}
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// An example of echo test with hardware flow control on UART
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static void echo_task(void *arg)
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{
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const int uart_num = ECHO_UART_PORT;
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uart_config_t uart_config = {
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.baud_rate = BAUD_RATE,
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.data_bits = UART_DATA_8_BITS,
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.parity = UART_PARITY_DISABLE,
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.stop_bits = UART_STOP_BITS_1,
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.flow_ctrl = UART_HW_FLOWCTRL_DISABLE,
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.rx_flow_ctrl_thresh = 122,
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.source_clk = UART_SCLK_DEFAULT,
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};
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// Set UART log level
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esp_log_level_set(TAG, ESP_LOG_INFO);
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ESP_LOGI(TAG, "Start RS485 application test and configure UART.");
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// Install UART driver (we don't need an event queue here)
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// In this example we don't even use a buffer for sending data.
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ESP_ERROR_CHECK(uart_driver_install(uart_num, BUF_SIZE * 2, 0, 0, NULL, 0));
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// Configure UART parameters
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ESP_ERROR_CHECK(uart_param_config(uart_num, &uart_config));
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ESP_LOGI(TAG, "UART set pins, mode and install driver.");
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// Set UART pins as per KConfig settings
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ESP_ERROR_CHECK(uart_set_pin(uart_num, ECHO_TEST_TXD, ECHO_TEST_RXD, ECHO_TEST_RTS, ECHO_TEST_CTS));
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// Set RS485 half duplex mode
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ESP_ERROR_CHECK(uart_set_mode(uart_num, UART_MODE_RS485_HALF_DUPLEX));
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// Set read timeout of UART TOUT feature
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ESP_ERROR_CHECK(uart_set_rx_timeout(uart_num, ECHO_READ_TOUT));
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// Allocate buffers for UART
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uint8_t* data = (uint8_t*) malloc(BUF_SIZE);
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assert(data);
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ESP_LOGI(TAG, "UART start receive loop.\r");
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echo_send(uart_num, "Start RS485 UART test.\r\n", 24);
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while (1) {
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//Read data from UART
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int len = uart_read_bytes(uart_num, data, BUF_SIZE, PACKET_READ_TICS);
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//Write data back to UART
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if (len > 0) {
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echo_send(uart_num, "\r\n", 2);
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char prefix[] = "RS485 Received: [";
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echo_send(uart_num, prefix, (sizeof(prefix) - 1));
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ESP_LOGI(TAG, "Received %u bytes:", len);
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printf("[ ");
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for (int i = 0; i < len; i++) {
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printf("0x%.2X ", (uint8_t)data[i]);
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echo_send(uart_num, (const char*)&data[i], 1);
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// Add a Newline character if you get a return character from paste (Paste tests multibyte receipt/buffer)
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if (data[i] == '\r') {
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echo_send(uart_num, "\n", 1);
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}
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}
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printf("] \n");
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echo_send(uart_num, "]\r\n", 3);
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}
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else {
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// Echo a "." to show we are alive while we wait for input
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echo_send(uart_num, ".", 1);
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ESP_ERROR_CHECK(uart_wait_tx_done(uart_num, 10));
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}
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}
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vTaskDelete(NULL);
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}
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void app_main(void)
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{
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//A uart read/write example without event queue;
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xTaskCreate(echo_task, "uart_echo_task", ECHO_TASK_STACK_SIZE, NULL, ECHO_TASK_PRIO, NULL);
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}
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