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84 lines
4.3 KiB
Markdown
84 lines
4.3 KiB
Markdown
# Modbus Master-Slave Example
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## Overview
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These two projects illustrate the communication between Modbus master and slave device in the segment.
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Master initializes Modbus interface driver and then reads parameters from slave device in the segment.
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After several successful read attempts slave sets the alarm relay (end of test condition).
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Once master reads the alarm it stops communication and destroy driver.
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The examples:
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* `examples/protocols/modbus/serial/mb_master` - Modbus serial master ASCII/RTU
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* `examples/protocols/modbus/serial/mb_slave` - Modbus serial slave ASCII/RTU
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See README.md for each individual project for more information.
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## How to use example
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### Hardware Required
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This example can be run on any commonly available ESP32 development board.
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The master and slave boards should be connected to each other through the RS485 interface line driver.
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See the connection schematic in README.md files of each example.
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### Configure the project
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This example test requires communication mode setting for master and slave be the same and slave address set to 1.
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Please refer to README.md files of each example project for more information.
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## About common_component in this example
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The folder "mb_example_common" includes definitions of parameter structures for master and slave device (both projects share the same parameters).
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However, currently it is for example purpose only and can be modified for particular application.
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## Example Output
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Example of Slave output:
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```
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I (343) SLAVE_TEST: Modbus slave stack initialized.
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I (343) SLAVE_TEST: Start modbus test...
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I (81463) SLAVE_TEST: HOLDING READ (81150420 us), ADDR:1, TYPE:2, INST_ADDR:0x3ffb2868, SIZE:6
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I (82463) SLAVE_TEST: HOLDING READ (82150720 us), ADDR:1, TYPE:2, INST_ADDR:0x3ffb2868, SIZE:6
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I (83573) SLAVE_TEST: HOLDING READ (83260630 us), ADDR:1, TYPE:2, INST_ADDR:0x3ffb2868, SIZE:6
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I (84603) SLAVE_TEST: HOLDING READ (84290530 us), ADDR:1, TYPE:2, INST_ADDR:0x3ffb2868, SIZE:6
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I (85703) SLAVE_TEST: HOLDING READ (85396692 us), ADDR:1, TYPE:2, INST_ADDR:0x3ffb2868, SIZE:6
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```
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Example of Modbus Master output:
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```
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I (399) MASTER_TEST: Modbus master stack initialized...
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I (499) MASTER_TEST: Start modbus test...
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I (549) MASTER_TEST: Characteristic #0 Data_channel_0 (Volts) value = 1.230000 (0x3f9d70a4) read successful.
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I (629) MASTER_TEST: Characteristic #1 Humidity_1 (%rH) value = 12.100000 (0x4141999a) read successful.
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I (709) MASTER_TEST: Characteristic #2 Temperature_1 (C) value = 3.560000 (0x4063d70a) read successful.
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I (769) MASTER_TEST: Characteristic #3 Humidity_2 (%rH) value = 23.400000 (0x41bb3333) read successful.
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I (829) MASTER_TEST: Characteristic #4 Temperature_2 (C) value = 5.890000 (0x40bc7ae1) read successful.
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I (889) MASTER_TEST: Characteristic #5 Humidity_3 (%rH) value = 34.500000 (0x420a0000) read successful.
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E (949) MB_CONTROLLER_MASTER: mbc_master_get_parameter(111): SERIAL master get parameter failure error=(0x108) (ESP_ERR_INVALID_RESPONSE).
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E (949) MASTER_TEST: Characteristic #6 (RelayP1) read fail, err = 264 (ESP_ERR_INVALID_RESPONSE).
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E (1029) MB_CONTROLLER_MASTER: mbc_master_get_parameter(111): SERIAL master get parameter failure error=(0x108) (ESP_ERR_INVALID_RESPONSE).
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E (1029) MASTER_TEST: Characteristic #7 (RelayP2) read fail, err = 264 (ESP_ERR_INVALID_RESPONSE).
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```
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## Troubleshooting
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If the examples do not work as expected and slave and master boards are not able to communicate correctly it is possible to find the reason for errors.
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The most important errors are described in master example output and formatted as below:
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```
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E (1692332) MB_CONTROLLER_MASTER: mbc_master_get_parameter(111): SERIAL master get parameter failure error=(0x107) (ESP_ERR_TIMEOUT).
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```
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ESP_ERR_TIMEOUT (0x107) - Modbus slave device does not respond during configured timeout. Check the connection and ability for communication using uart_echo_rs485 example or increase
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Kconfig value CONFIG_FMB_MASTER_TIMEOUT_MS_RESPOND (CONFIG_FMB_SERIAL_ASCII_TIMEOUT_RESPOND_MS).
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ESP_ERR_NOT_SUPPORTED (0x106), ESP_ERR_INVALID_RESPONSE (0x108) - Modbus slave device does not support requested command or register and sent exeption response.
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ESP_ERR_INVALID_STATE (0x103) - Modbus stack is not configured correctly or can't work correctly due to critical failure.
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Note: Refer to file below for more information about current implementation of Modbus:
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* `components/freemodbus/README.rst` |