Running Modbus Modubs TCP slave example on esp32 eth dev board

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zazas321
Posts: 231
Joined: Mon Feb 01, 2021 9:41 am

Running Modbus Modubs TCP slave example on esp32 eth dev board

Postby zazas321 » Mon Apr 17, 2023 10:03 am

I am learning about Modbus TCP. I have ESP32 Ethernet devboard:
https://docs.espressif.com/projects/esp ... t-kit.html

and I have flashed with the MODBUS TCP slave example:
https://github.com/espressif/esp-idf/tr ... _tcp_slave


My full code is here:

Code: Select all

/*
 * SPDX-FileCopyrightText: 2016-2022 Espressif Systems (Shanghai) CO LTD
 *
 * SPDX-License-Identifier: Apache-2.0
 */

// FreeModbus Slave Example ESP32

#include <stdio.h>
#include "esp_err.h"
#include "sdkconfig.h"
#include "esp_log.h"
#include "esp_system.h"
#include "esp_wifi.h"
#include "esp_event.h"
#include "esp_log.h"
#include "nvs_flash.h"

#include "mdns.h"
#include "esp_netif.h"
#include "protocol_examples_common.h"

#include "mbcontroller.h"       // for mbcontroller defines and api
#include "modbus_params.h"      // for modbus parameters structures

#define MB_TCP_PORT_NUMBER      (CONFIG_FMB_TCP_PORT_DEFAULT)
#define MB_MDNS_PORT            (502)

// Defines below are used to define register start address for each type of Modbus registers
#define HOLD_OFFSET(field) ((uint16_t)(offsetof(holding_reg_params_t, field) >> 1))
#define INPUT_OFFSET(field) ((uint16_t)(offsetof(input_reg_params_t, field) >> 1))
#define MB_REG_DISCRETE_INPUT_START         (0x0000)
#define MB_REG_COILS_START                  (0x0000)

#define MB_REG_INPUT_START_AREA0            (INPUT_OFFSET(input_data0)) // register offset input area 0
#define MB_REG_INPUT_START_AREA1            (INPUT_OFFSET(input_data4)) // register offset input area 1

#define MB_REG_HOLDING_START_AREA0          (HOLD_OFFSET(holding_data0))
#define MB_REG_HOLDING_START_AREA1          (HOLD_OFFSET(holding_data4))

#define MB_PAR_INFO_GET_TOUT                (10) // Timeout for get parameter info
#define MB_CHAN_DATA_MAX_VAL                (10)
#define MB_CHAN_DATA_OFFSET                 (1.1f)

#define MB_READ_MASK                        (MB_EVENT_INPUT_REG_RD \
                                                | MB_EVENT_HOLDING_REG_RD \
                                                | MB_EVENT_DISCRETE_RD \
                                                | MB_EVENT_COILS_RD)
#define MB_WRITE_MASK                       (MB_EVENT_HOLDING_REG_WR \
                                                | MB_EVENT_COILS_WR)
#define MB_READ_WRITE_MASK                  (MB_READ_MASK | MB_WRITE_MASK)

static const char *TAG = "SLAVE_TEST";

static portMUX_TYPE param_lock = portMUX_INITIALIZER_UNLOCKED;

#if CONFIG_MB_MDNS_IP_RESOLVER

#define MB_ID_BYTE0(id) ((uint8_t)(id))
#define MB_ID_BYTE1(id) ((uint8_t)(((uint16_t)(id) >> 8) & 0xFF))
#define MB_ID_BYTE2(id) ((uint8_t)(((uint32_t)(id) >> 16) & 0xFF))
#define MB_ID_BYTE3(id) ((uint8_t)(((uint32_t)(id) >> 24) & 0xFF))

#define MB_ID2STR(id) MB_ID_BYTE0(id), MB_ID_BYTE1(id), MB_ID_BYTE2(id), MB_ID_BYTE3(id)

#if CONFIG_FMB_CONTROLLER_SLAVE_ID_SUPPORT
#define MB_DEVICE_ID (uint32_t)CONFIG_FMB_CONTROLLER_SLAVE_ID
#endif

#define MB_SLAVE_ADDR (CONFIG_MB_SLAVE_ADDR)

#define MB_MDNS_INSTANCE(pref) pref"mb_slave_tcp"

// convert mac from binary format to string
static inline char* gen_mac_str(const uint8_t* mac, char* pref, char* mac_str)
{
    sprintf(mac_str, "%s%02X%02X%02X%02X%02X%02X", pref, MAC2STR(mac));
    return mac_str;
}

static inline char* gen_id_str(char* service_name, char* slave_id_str)
{
    sprintf(slave_id_str, "%s%02X%02X%02X%02X", service_name, MB_ID2STR(MB_DEVICE_ID));
    return slave_id_str;
}

static inline char* gen_host_name_str(char* service_name, char* name)
{
    sprintf(name, "%s_%02X", service_name, MB_SLAVE_ADDR);
    return name;
}

static void start_mdns_service(void)
{
    char temp_str[32] = {0};
    uint8_t sta_mac[6] = {0};
    ESP_ERROR_CHECK(esp_read_mac(sta_mac, ESP_MAC_WIFI_STA));
    char* hostname = gen_host_name_str(MB_MDNS_INSTANCE(""), temp_str);
    //initialize mDNS
    ESP_ERROR_CHECK(mdns_init());
    //set mDNS hostname (required if you want to advertise services)
    ESP_ERROR_CHECK(mdns_hostname_set(hostname));
    ESP_LOGI(TAG, "mdns hostname set to: [%s]", hostname);

    //set default mDNS instance name
    ESP_ERROR_CHECK(mdns_instance_name_set(MB_MDNS_INSTANCE("esp32_")));

    //structure with TXT records
    mdns_txt_item_t serviceTxtData[] = {
        {"board","esp32"}
    };

    //initialize service
    ESP_ERROR_CHECK(mdns_service_add(hostname, "_modbus", "_tcp", MB_MDNS_PORT, serviceTxtData, 1));
    //add mac key string text item
    ESP_ERROR_CHECK(mdns_service_txt_item_set("_modbus", "_tcp", "mac", gen_mac_str(sta_mac, "\0", temp_str)));
    //add slave id key txt item
    ESP_ERROR_CHECK( mdns_service_txt_item_set("_modbus", "_tcp", "mb_id", gen_id_str("\0", temp_str)));
}

static void stop_mdns_service(void)
{
    mdns_free();
}

#endif

// Set register values into known state
static void setup_reg_data(void)
{
    // Define initial state of parameters
    discrete_reg_params.discrete_input0 = 1;
    discrete_reg_params.discrete_input1 = 0;
    discrete_reg_params.discrete_input2 = 0;
    discrete_reg_params.discrete_input3 = 1;
    discrete_reg_params.discrete_input4 = 0;


    discrete_reg_params.discrete_input5 = 1;
    discrete_reg_params.discrete_input6 = 0;
    discrete_reg_params.discrete_input7 = 0;


    holding_reg_params.holding_data0 = 1.34;
    holding_reg_params.holding_data1 = 2.56;
    holding_reg_params.holding_data2 = 3.78;
    holding_reg_params.holding_data3 = 4.90;

    holding_reg_params.holding_data4 = 5.67;
    holding_reg_params.holding_data5 = 6.78;
    holding_reg_params.holding_data6 = 7.79;
    holding_reg_params.holding_data7 = 8.80;
    coil_reg_params.coils_port0 = 0x55;
    coil_reg_params.coils_port1 = 0xAA;

    input_reg_params.input_data0 = 1.12;
    input_reg_params.input_data1 = 2.34;
    input_reg_params.input_data2 = 3.56;
    input_reg_params.input_data3 = 4.78;
    input_reg_params.input_data4 = 5.55;
    input_reg_params.input_data5 = 6.77;
/*
    input_reg_params.input_data4 = 1.12;
    input_reg_params.input_data5 = 2.34;
    input_reg_params.input_data6 = 3.56;
    input_reg_params.input_data7 = 4.78;
    */
}

static void slave_operation_func(void *arg)
{
    mb_param_info_t reg_info; // keeps the Modbus registers access information

    ESP_LOGI(TAG, "Modbus slave stack initialized.");
    ESP_LOGI(TAG, "Start modbus test...");
    // The cycle below will be terminated when parameter holding_data0
    // incremented each access cycle reaches the CHAN_DATA_MAX_VAL value.
    for(;holding_reg_params.holding_data0 < MB_CHAN_DATA_MAX_VAL;) {
        // Check for read/write events of Modbus master for certain events
        mb_event_group_t event = mbc_slave_check_event(MB_READ_WRITE_MASK);
        const char* rw_str = (event & MB_READ_MASK) ? "READ" : "WRITE";
        // Filter events and process them accordingly
        if(event & (MB_EVENT_HOLDING_REG_WR | MB_EVENT_HOLDING_REG_RD)) {
            // Get parameter information from parameter queue
            ESP_ERROR_CHECK(mbc_slave_get_param_info(&reg_info, MB_PAR_INFO_GET_TOUT));
            ESP_LOGI(TAG, "HOLDING %s (%u us), ADDR:%u, TYPE:%u, INST_ADDR:0x%.4x, SIZE:%u",
                    rw_str,
                    (uint32_t)reg_info.time_stamp,
                    (uint32_t)reg_info.mb_offset,
                    (uint32_t)reg_info.type,
                    (uint32_t)reg_info.address,
                    (uint32_t)reg_info.size);
            if (reg_info.address == (uint8_t*)&holding_reg_params.holding_data0)
            {
                portENTER_CRITICAL(&param_lock);
                holding_reg_params.holding_data0 += MB_CHAN_DATA_OFFSET;
                if (holding_reg_params.holding_data0 >= (MB_CHAN_DATA_MAX_VAL - MB_CHAN_DATA_OFFSET)) {
                    coil_reg_params.coils_port1 = 0xFF;
                }
                portEXIT_CRITICAL(&param_lock);
            }
        } else if (event & MB_EVENT_INPUT_REG_RD) {
            ESP_ERROR_CHECK(mbc_slave_get_param_info(&reg_info, MB_PAR_INFO_GET_TOUT));
            ESP_LOGI(TAG, "INPUT READ (%u us), ADDR:%u, TYPE:%u, INST_ADDR:0x%.4x, SIZE:%u",
                    (uint32_t)reg_info.time_stamp,
                    (uint32_t)reg_info.mb_offset,
                    (uint32_t)reg_info.type,
                    (uint32_t)reg_info.address,
                    (uint32_t)reg_info.size);
        } else if (event & MB_EVENT_DISCRETE_RD) {
            ESP_ERROR_CHECK(mbc_slave_get_param_info(&reg_info, MB_PAR_INFO_GET_TOUT));
            ESP_LOGI(TAG, "DISCRETE READ (%u us): ADDR:%u, TYPE:%u, INST_ADDR:0x%.4x, SIZE:%u",
                                (uint32_t)reg_info.time_stamp,
                                (uint32_t)reg_info.mb_offset,
                                (uint32_t)reg_info.type,
                                (uint32_t)reg_info.address,
                                (uint32_t)reg_info.size);
        } else if (event & (MB_EVENT_COILS_RD | MB_EVENT_COILS_WR)) {
            ESP_ERROR_CHECK(mbc_slave_get_param_info(&reg_info, MB_PAR_INFO_GET_TOUT));
            ESP_LOGI(TAG, "COILS %s (%u us), ADDR:%u, TYPE:%u, INST_ADDR:0x%.4x, SIZE:%u",
                                rw_str,
                                (uint32_t)reg_info.time_stamp,
                                (uint32_t)reg_info.mb_offset,
                                (uint32_t)reg_info.type,
                                (uint32_t)reg_info.address,
                                (uint32_t)reg_info.size);
            if (coil_reg_params.coils_port1 == 0xFF) break;
        }
    }
    // Destroy of Modbus controller on alarm
    ESP_LOGI(TAG,"Modbus controller destroyed.");
    vTaskDelay(100);
}

static esp_err_t init_services(void)
{
    esp_err_t result = nvs_flash_init();
    if (result == ESP_ERR_NVS_NO_FREE_PAGES || result == ESP_ERR_NVS_NEW_VERSION_FOUND) {
      ESP_ERROR_CHECK(nvs_flash_erase());
      result = nvs_flash_init();
    }
    MB_RETURN_ON_FALSE((result == ESP_OK), ESP_ERR_INVALID_STATE,
                            TAG,
                            "nvs_flash_init fail, returns(0x%x).",
                            (uint32_t)result);
    result = esp_netif_init();
    MB_RETURN_ON_FALSE((result == ESP_OK), ESP_ERR_INVALID_STATE,
                            TAG,
                            "esp_netif_init fail, returns(0x%x).",
                            (uint32_t)result);
    result = esp_event_loop_create_default();
    MB_RETURN_ON_FALSE((result == ESP_OK), ESP_ERR_INVALID_STATE,
                            TAG,
                            "esp_event_loop_create_default fail, returns(0x%x).",
                            (uint32_t)result);
#if CONFIG_MB_MDNS_IP_RESOLVER
    // Start mdns service and register device
    start_mdns_service();
#endif
    // This helper function configures Wi-Fi or Ethernet, as selected in menuconfig.
    // Read "Establishing Wi-Fi or Ethernet Connection" section in
    // examples/protocols/README.md for more information about this function.
    result = example_connect();
    MB_RETURN_ON_FALSE((result == ESP_OK), ESP_ERR_INVALID_STATE,
                                TAG,
                                "example_connect fail, returns(0x%x).",
                                (uint32_t)result);
#if CONFIG_EXAMPLE_CONNECT_WIFI
    result = esp_wifi_set_ps(WIFI_PS_NONE);
    MB_RETURN_ON_FALSE((result == ESP_OK), ESP_ERR_INVALID_STATE,
                                   TAG,
                                   "esp_wifi_set_ps fail, returns(0x%x).",
                                   (uint32_t)result);
#endif
    return ESP_OK;
}

static esp_err_t destroy_services(void)
{
    esp_err_t err = ESP_OK;

    err = example_disconnect();
    MB_RETURN_ON_FALSE((err == ESP_OK), ESP_ERR_INVALID_STATE,
                                   TAG,
                                   "example_disconnect fail, returns(0x%x).",
                                   (uint32_t)err);
    err = esp_event_loop_delete_default();
    MB_RETURN_ON_FALSE((err == ESP_OK), ESP_ERR_INVALID_STATE,
                                       TAG,
                                       "esp_event_loop_delete_default fail, returns(0x%x).",
                                       (uint32_t)err);
    err = esp_netif_deinit();
    MB_RETURN_ON_FALSE((err == ESP_OK || err == ESP_ERR_NOT_SUPPORTED), ESP_ERR_INVALID_STATE,
                                        TAG,
                                        "esp_netif_deinit fail, returns(0x%x).",
                                        (uint32_t)err);
    err = nvs_flash_deinit();
    MB_RETURN_ON_FALSE((err == ESP_OK), ESP_ERR_INVALID_STATE,
                                TAG,
                                "nvs_flash_deinit fail, returns(0x%x).",
                                (uint32_t)err);
#if CONFIG_MB_MDNS_IP_RESOLVER
    stop_mdns_service();
#endif
    return err;
}

// Modbus slave initialization
static esp_err_t slave_init(mb_communication_info_t* comm_info)
{
    mb_register_area_descriptor_t reg_area; // Modbus register area descriptor structure

    void* slave_handler = NULL;

    // Initialization of Modbus controller
    esp_err_t err = mbc_slave_init_tcp(&slave_handler);
    MB_RETURN_ON_FALSE((err == ESP_OK && slave_handler != NULL), ESP_ERR_INVALID_STATE,
                                TAG,
                                "mb controller initialization fail.");

    comm_info->ip_addr = NULL; // Bind to any address
    comm_info->ip_netif_ptr = (void*)get_example_netif();

    // Setup communication parameters and start stack
    err = mbc_slave_setup((void*)comm_info);
    MB_RETURN_ON_FALSE((err == ESP_OK), ESP_ERR_INVALID_STATE,
                                        TAG,
                                        "mbc_slave_setup fail, returns(0x%x).",
                                        (uint32_t)err);

    // The code below initializes Modbus register area descriptors
    // for Modbus Holding Registers, Input Registers, Coils and Discrete Inputs
    // Initialization should be done for each supported Modbus register area according to register map.
    // When external master trying to access the register in the area that is not initialized
    // by mbc_slave_set_descriptor() API call then Modbus stack
    // will send exception response for this register area.
    reg_area.type = MB_PARAM_HOLDING; // Set type of register area
    reg_area.start_offset = MB_REG_HOLDING_START_AREA0; // Offset of register area in Modbus protocol
    reg_area.address = (void*)&holding_reg_params.holding_data0; // Set pointer to storage instance
    reg_area.size = sizeof(float) << 2; // Set the size of register storage instance
    err = mbc_slave_set_descriptor(reg_area);
    MB_RETURN_ON_FALSE((err == ESP_OK), ESP_ERR_INVALID_STATE,
                                    TAG,
                                    "mbc_slave_set_descriptor fail, returns(0x%x).",
                                    (uint32_t)err);

    reg_area.type = MB_PARAM_HOLDING; // Set type of register area
    reg_area.start_offset = MB_REG_HOLDING_START_AREA1; // Offset of register area in Modbus protocol
    reg_area.address = (void*)&holding_reg_params.holding_data4; // Set pointer to storage instance
    reg_area.size = sizeof(float) << 2; // Set the size of register storage instance
    err = mbc_slave_set_descriptor(reg_area);
    MB_RETURN_ON_FALSE((err == ESP_OK), ESP_ERR_INVALID_STATE,
                                    TAG,
                                    "mbc_slave_set_descriptor fail, returns(0x%x).",
                                    (uint32_t)err);

    // Initialization of Input Registers area
    reg_area.type = MB_PARAM_INPUT;
    reg_area.start_offset = MB_REG_INPUT_START_AREA0;
    reg_area.address = (void*)&input_reg_params.input_data0;
    reg_area.size = sizeof(float) << 2;
    err = mbc_slave_set_descriptor(reg_area);
    MB_RETURN_ON_FALSE((err == ESP_OK), ESP_ERR_INVALID_STATE,
                                        TAG,
                                        "mbc_slave_set_descriptor fail, returns(0x%x).",
                                        (uint32_t)err);

    reg_area.type = MB_PARAM_INPUT;
    reg_area.start_offset = MB_REG_INPUT_START_AREA1;
    reg_area.address = (void*)&input_reg_params.input_data4;
    reg_area.size = sizeof(float) << 2;
    err = mbc_slave_set_descriptor(reg_area);
    MB_RETURN_ON_FALSE((err == ESP_OK), ESP_ERR_INVALID_STATE,
                                        TAG,
                                        "mbc_slave_set_descriptor fail, returns(0x%x).",
                                        (uint32_t)err);

    // Initialization of Coils register area
    reg_area.type = MB_PARAM_COIL;
    reg_area.start_offset = MB_REG_COILS_START;
    reg_area.address = (void*)&coil_reg_params;
    reg_area.size = sizeof(coil_reg_params);
    err = mbc_slave_set_descriptor(reg_area);
    MB_RETURN_ON_FALSE((err == ESP_OK), ESP_ERR_INVALID_STATE,
                                    TAG,
                                    "mbc_slave_set_descriptor fail, returns(0x%x).",
                                    (uint32_t)err);

    // Initialization of Discrete Inputs register area
    reg_area.type = MB_PARAM_DISCRETE;
    reg_area.start_offset = MB_REG_DISCRETE_INPUT_START;
    reg_area.address = (void*)&discrete_reg_params;
    reg_area.size = sizeof(discrete_reg_params);
    err = mbc_slave_set_descriptor(reg_area);
    MB_RETURN_ON_FALSE((err == ESP_OK), ESP_ERR_INVALID_STATE,
                                    TAG,
                                    "mbc_slave_set_descriptor fail, returns(0x%x).",
                                    (uint32_t)err);

    // Set values into known state
    setup_reg_data();

    // Starts of modbus controller and stack
    err = mbc_slave_start();
    MB_RETURN_ON_FALSE((err == ESP_OK), ESP_ERR_INVALID_STATE,
                                        TAG,
                                        "mbc_slave_start fail, returns(0x%x).",
                                        (uint32_t)err);
    vTaskDelay(5);
    return err;
}

static esp_err_t slave_destroy(void)
{
    esp_err_t err = mbc_slave_destroy();
    MB_RETURN_ON_FALSE((err == ESP_OK), ESP_ERR_INVALID_STATE,
                                TAG,
                                "mbc_slave_destroy fail, returns(0x%x).",
                                (uint32_t)err);
    return err;
}

// An example application of Modbus slave. It is based on freemodbus stack.
// See deviceparams.h file for more information about assigned Modbus parameters.
// These parameters can be accessed from main application and also can be changed
// by external Modbus master host.
void app_main(void)
{
    ESP_ERROR_CHECK(init_services());

    // Set UART log level
    //esp_log_level_set(TAG, ESP_LOG_INFO);

    mb_communication_info_t comm_info = { 0 };

#if !CONFIG_EXAMPLE_CONNECT_IPV6
    comm_info.ip_addr_type = MB_IPV4;
#else
    comm_info.ip_addr_type = MB_IPV6;
#endif
    comm_info.ip_mode = MB_MODE_TCP;

    comm_info.ip_port = MB_TCP_PORT_NUMBER;
    ESP_ERROR_CHECK(slave_init(&comm_info));

    // The Modbus slave logic is located in this function (user handling of Modbus)
    slave_operation_func(NULL);

    ESP_ERROR_CHECK(slave_destroy());
    ESP_ERROR_CHECK(destroy_services());
}
To simulate modbus master, I use the following tool:
https://sourceforge.net/projects/qmodmaster/





In my code, I setup the initial registers:

Code: Select all

static void setup_reg_data(void)
{
    // Define initial state of parameters
    discrete_reg_params.discrete_input0 = 1;
    discrete_reg_params.discrete_input1 = 0;
    discrete_reg_params.discrete_input2 = 0;
    discrete_reg_params.discrete_input3 = 1;
    discrete_reg_params.discrete_input4 = 0;


    discrete_reg_params.discrete_input5 = 1;
    discrete_reg_params.discrete_input6 = 0;
    discrete_reg_params.discrete_input7 = 0;


    holding_reg_params.holding_data0 = 1.34;
    holding_reg_params.holding_data1 = 2.56;
    holding_reg_params.holding_data2 = 3.78;
    holding_reg_params.holding_data3 = 4.90;

    holding_reg_params.holding_data4 = 5.67;
    holding_reg_params.holding_data5 = 6.78;
    holding_reg_params.holding_data6 = 7.79;
    holding_reg_params.holding_data7 = 8.80;
    coil_reg_params.coils_port0 = 0x55;
    coil_reg_params.coils_port1 = 0xAA;

    input_reg_params.input_data0 = 1.12;
    input_reg_params.input_data1 = 2.34;
    input_reg_params.input_data2 = 3.56;
    input_reg_params.input_data3 = 4.78;
    input_reg_params.input_data4 = 5.55;
    input_reg_params.input_data5 = 6.77;

}
Notice that input registers are set to following:

Code: Select all

input_data0 is set to 1.12
input_data1 is set to 2.34
input_data2 is set to 3.56
input_data3 is set to 4.78
input_data4 is set to 5.55
input_data5 is set to 6.77
In the slave_init function, the HOLDING and INPUT are split into two different areas as shown below:

Code: Select all

// The code below initializes Modbus register area descriptors
    // for Modbus Holding Registers, Input Registers, Coils and Discrete Inputs
    // Initialization should be done for each supported Modbus register area according to register map.
    // When external master trying to access the register in the area that is not initialized
    // by mbc_slave_set_descriptor() API call then Modbus stack
    // will send exception response for this register area.
    reg_area.type = MB_PARAM_HOLDING; // Set type of register area
    reg_area.start_offset = MB_REG_HOLDING_START_AREA0; // Offset of register area in Modbus protocol
    reg_area.address = (void*)&holding_reg_params.holding_data0; // Set pointer to storage instance
    reg_area.size = sizeof(float) << 2; // Set the size of register storage instance
    err = mbc_slave_set_descriptor(reg_area);
    MB_RETURN_ON_FALSE((err == ESP_OK), ESP_ERR_INVALID_STATE,
                                    TAG,
                                    "mbc_slave_set_descriptor fail, returns(0x%x).",
                                    (uint32_t)err);

    reg_area.type = MB_PARAM_HOLDING; // Set type of register area
    reg_area.start_offset = MB_REG_HOLDING_START_AREA1; // Offset of register area in Modbus protocol
    reg_area.address = (void*)&holding_reg_params.holding_data4; // Set pointer to storage instance
    reg_area.size = sizeof(float) << 2; // Set the size of register storage instance
    err = mbc_slave_set_descriptor(reg_area);
    MB_RETURN_ON_FALSE((err == ESP_OK), ESP_ERR_INVALID_STATE,
                                    TAG,
                                    "mbc_slave_set_descriptor fail, returns(0x%x).",
                                    (uint32_t)err);

    // Initialization of Input Registers area
    reg_area.type = MB_PARAM_INPUT;
    reg_area.start_offset = MB_REG_INPUT_START_AREA0;
    reg_area.address = (void*)&input_reg_params.input_data0;
    reg_area.size = sizeof(float) << 2;
    err = mbc_slave_set_descriptor(reg_area);
    MB_RETURN_ON_FALSE((err == ESP_OK), ESP_ERR_INVALID_STATE,
                                        TAG,
                                        "mbc_slave_set_descriptor fail, returns(0x%x).",
                                        (uint32_t)err);

    

    reg_area.type = MB_PARAM_INPUT;
    reg_area.start_offset = MB_REG_INPUT_START_AREA1;
    reg_area.address = (void*)&input_reg_params.input_data4;
    reg_area.size = sizeof(float) << 2;
    err = mbc_slave_set_descriptor(reg_area);
    MB_RETURN_ON_FALSE((err == ESP_OK), ESP_ERR_INVALID_STATE,
                                        TAG,
                                        "mbc_slave_set_descriptor fail, returns(0x%x).",
                                        (uint32_t)err);

My questions:

1. Why the INPUT and HOLDING registers are split into 2 different areas?

I would have expected register offsets to be set as following:

1-9999 - coils
10001-19999 - Discrete Inputs
30001-39999 - Input registers
40001-49999 - Holding registers

from the code I see:

Code: Select all

#define MB_REG_DISCRETE_INPUT_START         (0x0000)
#define MB_REG_COILS_START                  (0x0000)

#define MB_REG_INPUT_START_AREA0            (INPUT_OFFSET(input_data0)) // register offset input area 0
#define MB_REG_INPUT_START_AREA1            (INPUT_OFFSET(input_data4)) // register offset input area 1

#define MB_REG_HOLDING_START_AREA0          (HOLD_OFFSET(holding_data0))
#define MB_REG_HOLDING_START_AREA1          (HOLD_OFFSET(holding_data4))
And is not fully clear to me


2. It does not allow me to read more than first 8 registers of INPUT or HOLDING
Here I read first 8 registers and the values are as expected:
https://ibb.co/zZZPgHG

Here I try to read 10 registers and it fails:
https://ibb.co/fYSxzKW

When I try to read first 10 registers of INPUT , I expect to get:

Code: Select all

    input_reg_params.input_data0 = 1.12;
    input_reg_params.input_data1 = 2.34;
    input_reg_params.input_data2 = 3.56;
    input_reg_params.input_data3 = 4.78;
    input_reg_params.input_data4 = 5.55;

3. I do not fully understand what are those parameters:

Code: Select all

#define MB_CHAN_DATA_MAX_VAL                (10)
#define MB_CHAN_DATA_OFFSET                 (1.1f)



Thanks in advance for any help...
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ESP_alisitsyn
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Re: Running Modbus Modubs TCP slave example on esp32 eth dev board

Postby ESP_alisitsyn » Tue Jun 06, 2023 9:41 am

@zazas321,

The example simulates the communication with modbus device. You can change it how you need in your project.
1. Why the INPUT and HOLDING registers are split into 2 different areas?
A: This is to show how you can define two separate address areas in your modbus project. You can configure areas as you need in your project. This is just a demonstration of API.
When I try to read first 10 registers of INPUT , I expect to get:
A: In the example the two areas are configured and length of them = 4 float values. The reading outside of registered area causes an error. See the documentation provided here https://docs.espressif.com/projects/esp ... ata-access for more information on how to configure the code.

3. I do not fully understand what are those parameters:
A: In order to check the example with the external host tool as Qmodbus the slave example simulates the changing of the value with the increment of MB_CHAN_DATA_OFFSET each read cycle. Once it reaches the MB_CHAN_DATA_MAX_VAL value, the slave will be automatically destroy itself. This is what the example does.

Please read the documentation and example readme.md file to get more information.
I would have expected register offsets to be set as following:
The esp-modbus API uses the zero based address in each area. The https://docs.espressif.com/projects/esp ... .html#id1 .
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