ESP32 Forum

Posted: **Tue Feb 11, 2025 3:24 pm**

For some reasons I am working on ESP-IDF 4.4.5 and I'm trying to use esp-modbus to connect to some slaves. I did the connection with the ESP32 on serial master and it was all OK. Now I'm trying to connect the ESP32 (tcp master) with a slave simulator and a real slave device. The error that I am facing is at the mbc_master_start() function, when he can not found any slave device. I tested myself to connect to that slave simulator from other device and it works ok. The IP address is OK. I don't know why the Host IP is the same as the slave IP but I've seen in other projects in the forum they could make it work. Why mbc_master_start() is not working? Thank you

I (00:00:24.525) NETWORK: ESP32 Host IP: 192.168.3.59
E (00:00:24.526) TAG: mbc_master_init OK: ESP_OK
E (00:00:24.526) TAG: mbc_master_setup OK: ESP_OK
E (00:00:24.531) TAG: mbc_master_set_descriptor OK: ESP_OK
I (00:00:24.537) MB_TCP_MASTER_PORT: TCP master stack initialized.
I (00:00:24.545) MB_TCP_MASTER_PORT: Host IP: [192.168.3.36]
I (00:00:24.551) MB_TCP_MASTER_PORT: Add slave IP: 192.168.3.36
I (00:00:24.557) MB_TCP_MASTER_PORT: Connecting to slaves...
-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.
E (00:01:24.563) MB_CONTROLLER_MASTER: mbc_tcp_master_start(179): mb stack could not connect to slaves for 60 seconds.
E (00:01:24.565) MB_CONTROLLER_MASTER: mbc_master_start(179): Master start failure, error=(0x103) (ESP_ERR_INVALID_STATE).
E (00:01:24.577) TAG: Error mbc_master_start: ESP_ERR_INVALID_STATE

Code: Select all

[Codebox=cpp file=Untitled.cpp]
char* slave_ip_address_table[1] = {
        "192.168.3.36",
    };
    const size_t ip_table_sz = (size_t)(sizeof(slave_ip_address_table) / sizeof(slave_ip_address_table[0]));

    esp_netif_ip_info_t ip_info;
    esp_netif_t *netif = esp_netif_get_handle_from_ifkey("WIFI_STA_DEF"); // Para WiFi en modo estación
    if (netif == NULL) {
        ESP_LOGE("NETWORK", "No se encontró la interfaz de red.");
        return;
    }

    esp_netif_get_ip_info(netif, &ip_info);
    ip4_addr_t ip_addr;
    ip_addr.addr = ip_info.ip.addr;
    ESP_LOGI("NETWORK", "ESP32 Host IP: %s", ip4addr_ntoa(&ip_addr));

    // Initialize and start Modbus controller
    mb_communication_info_t comm1 = {};
    comm1.mode = MB_MODE_TCP;
    comm1.port = 502;
    comm1.ip_addr_type = MB_IPV4;
    comm1.ip_addr = (void*) slave_ip_address_table;
    comm1.ip_netif_ptr = netif;
    
    void* master_handler = NULL;
    // mbc_master_init_iface(&master_handler);
    esp_err_t err_init = mbc_master_init_tcp(&master_handler);
    if (err_init != ESP_OK) {
        ESP_LOGE("TAG", "Error mbc_master_init: %s", esp_err_to_name(err_init));
    } else {
        ESP_LOGE("TAG", "mbc_master_init OK: %s", esp_err_to_name(err_init));
    }

    esp_err_t err_setup = mbc_master_setup((void*)&comm1);
    if (err_setup != ESP_OK) {
        ESP_LOGE("TAG", "Error mbc_master_setup: %s", esp_err_to_name(err_setup));
    } else {
        ESP_LOGE("TAG", "mbc_master_setup OK: %s", esp_err_to_name(err_init));
    }

    esp_err_t err_descriptor = mbc_master_set_descriptor(&device_parameters1[0], num_device_parameters1);
    if (err_descriptor != ESP_OK) {
        ESP_LOGE("TAG", "Error mbc_master_set_descriptor: %s", esp_err_to_name(err_descriptor));
    } else {
        ESP_LOGE("TAG", "mbc_master_set_descriptor OK: %s", esp_err_to_name(err_descriptor));
    }

    esp_err_t err_start = mbc_master_start();
    if (err_start != ESP_OK) {
        ESP_LOGE("TAG", "Error mbc_master_start: %s", esp_err_to_name(err_start));
    } else {
        ESP_LOGE("TAG", "mbc_master_start OK: %s", esp_err_to_name(err_start));
    }
    [/Codebox]

Edit:
I used "set(EXCLUDE_COMPONENTS "freemodbus")" on the project's CmakeLists.txt (I don't know if the order in that file is important.
The esp-modbus version is 1.0.17 (to make it work on ESP-IDF 4.3 and 4.4.5).
My sdkconfig related to the modbus configurated is:

#
# Modbus configuration
#
CONFIG_FMB_COMM_MODE_TCP_EN=y
CONFIG_FMB_TCP_PORT_DEFAULT=502
CONFIG_FMB_TCP_PORT_MAX_CONN=5
CONFIG_FMB_TCP_CONNECTION_TOUT_SEC=60
CONFIG_FMB_COMM_MODE_RTU_EN=y
CONFIG_FMB_COMM_MODE_ASCII_EN=y
CONFIG_FMB_MASTER_TIMEOUT_MS_RESPOND=1500
CONFIG_FMB_MASTER_DELAY_MS_CONVERT=200
CONFIG_FMB_QUEUE_LENGTH=20
CONFIG_FMB_PORT_TASK_STACK_SIZE=4096
CONFIG_FMB_SERIAL_BUF_SIZE=256
CONFIG_FMB_SERIAL_ASCII_BITS_PER_SYMB=8
CONFIG_FMB_SERIAL_ASCII_TIMEOUT_RESPOND_MS=1000
CONFIG_FMB_PORT_TASK_PRIO=10
# CONFIG_FMB_PORT_TASK_AFFINITY_NO_AFFINITY is not set
CONFIG_FMB_PORT_TASK_AFFINITY_CPU0=y
# CONFIG_FMB_PORT_TASK_AFFINITY_CPU1 is not set
CONFIG_FMB_PORT_TASK_AFFINITY=0x0
CONFIG_FMB_CONTROLLER_SLAVE_ID_SUPPORT=y
CONFIG_FMB_CONTROLLER_SLAVE_ID=0x00112233
CONFIG_FMB_CONTROLLER_NOTIFY_TIMEOUT=20
CONFIG_FMB_CONTROLLER_NOTIFY_QUEUE_SIZE=20
CONFIG_FMB_CONTROLLER_STACK_SIZE=4096
CONFIG_FMB_EVENT_QUEUE_TIMEOUT=20
CONFIG_FMB_TIMER_PORT_ENABLED=y
# CONFIG_FMB_TIMER_USE_ISR_DISPATCH_METHOD is not set
# end of Modbus configuration

Posted: **Fri Feb 14, 2025 8:31 am**

@daannii10,

Please add the NULL in the ip address table. This should solve the issue.

Code: Select all

char* slave_ip_address_table[] = {
        "192.168.3.36",
        NULL
    };

https://docs.espressif.com/projects/esp ... on-options

Posted: **Fri Feb 14, 2025 12:24 pm**

Thank you for your response but that did not solve the problem. I tried the same code you posted and did not compile.

error: too many initializers for 'char* [1]'
};

If I put "char* slave_ip_address_table[2]" or even "char* slave_ip_address_table[]" it compiles but same output as the previous code. Can't start.

Posted: **Mon Feb 24, 2025 7:42 am**

Hello, any other solution? Thank you

Posted: **Mon Feb 24, 2025 9:18 am**

I just missed the array count change. There are two possible reasons for the issue with the connection you mentioned.

1. The issue with the slave_ip_address_table[]. The NULL in the last element is required without it the master will not able to connect and it is most possible reason for the issue (as per your log). Please then do

Code: Select all

idf.py fullclean; idf.py build

to rebuild the application.
2. Network issue. Check the slave connection and if the slave correctly initiated and can communicate with the master. Use the application on the host computer to check.

Code: Select all

char* slave_ip_address_table[] = { // global scope array for master app
        "192.168.3.36",
        NULL // Required terminator for the address list.
    };

ESP32 Forum

mbc_master_start() can not connect to slaves

mbc_master_start() can not connect to slaves

Re: mbc_master_start() can not connect to slaves

Re: mbc_master_start() can not connect to slaves

Re: mbc_master_start() can not connect to slaves

Re: mbc_master_start() can not connect to slaves