base on A compact MODBUS RTU/TCP C library for embedded/microcontrollers # nanoMODBUS - A compact MODBUS RTU/TCP C library for embedded/microcontrollers **If you found this library useful, buy me a coffee on** [<img src='https://storage.ko-fi.com/cdn/brandasset/logo_white_stroke.png' width='80'>](https://ko-fi.com/B0B2LK779) nanoMODBUS is a small C library that implements the Modbus protocol. It is especially useful in embedded and resource-constrained systems like microcontrollers. Its main features are: - Compact size - Only ~2000 lines of code - Client and server code can be disabled, if not needed - No dynamic memory allocations - Transports: - RTU - TCP - Roles: - Client - Server - Function codes: - 01 (0x01) Read Coils - 02 (0x02) Read Discrete Inputs - 03 (0x03) Read Holding Registers - 04 (0x04) Read Input Registers - 05 (0x05) Write Single Coil - 06 (0x06) Write Single Register - 15 (0x0F) Write Multiple Coils - 16 (0x10) Write Multiple registers - 20 (0x14) Read File Record - 21 (0x15) Write File Record - 23 (0x17) Read/Write Multiple registers - 43/14 (0x2B/0x0E) Read Device Identification - Platform-agnostic - Requires only C99 and its standard library - Data transport read/write functions are implemented by the user - User-definable CRC function for better performance - Broadcast requests and responses ## At a glance ```C #include <stdio.h> #include "nanomodbus.h" #include "my_platform_stuff.h" int main(int argc, char* argv[]) { // Set up the TCP connection void* conn = my_connect_tcp(argv[1], argv[2]); if (!conn) { fprintf(stderr, "Error connecting to server\n"); return 1; } // my_transport_read() and my_transport_write() are implemented by the user nmbs_platform_conf platform_conf; nmbs_platform_conf_create(&platform_conf); platform_conf.transport = NMBS_TRANSPORT_TCP; platform_conf.read = my_transport_read; platform_conf.write = my_transport_write; platform_conf.arg = conn; // Passing our TCP connection handle to the read/write functions // Create the modbus client nmbs_t nmbs; nmbs_error err = nmbs_client_create(&nmbs, &platform_conf); if (err != NMBS_ERROR_NONE) { fprintf(stderr, "Error creating modbus client\n"); return 1; } // Set only the response timeout. Byte timeout will be handled by the TCP connection nmbs_set_read_timeout(&nmbs, 1000); // Write 2 holding registers at address 26 uint16_t w_regs[2] = {123, 124}; err = nmbs_write_multiple_registers(&nmbs, 26, 2, w_regs); if (err != NMBS_ERROR_NONE) { fprintf(stderr, "Error writing register at address 26 - %s", nmbs_strerror(err)); return 1; } // Read 2 holding registers from address 26 uint16_t r_regs[2]; err = nmbs_read_holding_registers(&nmbs, 26, 2, r_regs); if (err != NMBS_ERROR_NONE) { fprintf(stderr, "Error reading 2 holding registers at address 26 - %s\n", nmbs_strerror(err)); return 1; } // Close the TCP connection my_disconnect(conn); return 0; } ``` ## Installation ### Manual Just copy `nanomodbus.c` and `nanomodbus.h` inside your application codebase. ### CMake project nanomodbus supports library linking by using CMake. ```cmake FetchContent_Declare( nanomodbus GIT_REPOSITORY https://github.com/debevv/nanoMODBUS GIT_TAG master # or the version you want GIT_SHALLOW TRUE ) FetchContent_MakeAvailable(nanomodbus) ... add_executable(your_program source_codes) target_link_libraries(your_program nanomodbus) ``` ## API reference API reference is available in the repository's [GitHub Pages](https://debevv.github.io/nanoMODBUS/nanomodbus_8h.html). ## Platform functions nanoMODBUS requires the implementation of 2 platform-specific functions, defined as function pointers when creating a client/server instance. ### Transport read/write ```C int32_t read(uint8_t* buf, uint16_t count, int32_t byte_timeout_ms, void* arg); int32_t write(const uint8_t* buf, uint16_t count, int32_t byte_timeout_ms, void* arg); ``` These are your platform-specific functions that read/write data to/from a serial port or a TCP connection. Both methods should block until either: - `count` bytes of data are read/written - the byte timeout, with `byte_timeout_ms >= 0`, expires A value `< 0` for `byte_timeout_ms` means infinite timeout. With a value `== 0` for `byte_timeout_ms`, the method should read/write once in a non-blocking fashion and return immediately. Their return value should be the number of bytes actually read/written, or `< 0` in case of error. A return value between `0` and `count - 1` will be treated as if a timeout occurred on the transport side. All other values will be treated as transport errors. ### Callbacks and platform functions arguments Server callbacks and platform functions can access arbitrary user data through their `void* arg` argument. The argument is useful, for example, to pass the connection a function should operate on. Their initial values can be set via the `nmbs_set_callbacks_arg` and `nmbs_set_platform_arg` API methods. ## Tests and examples Tests and examples can be built and run on Linux with CMake: ```sh mkdir build && cd build cmake .. make ``` Please refer to `examples/arduino/README.md` for more info about building and running Arduino examples. ## Misc - To reduce code size, you can define the following `#define`s: - `NMBS_CLIENT_DISABLED` to disable all client code - `NMBS_SERVER_DISABLED` to disable all server code - To disable individual server callbacks, define the following: - `NMBS_SERVER_READ_COILS_DISABLED` - `NMBS_SERVER_READ_DISCRETE_INPUTS_DISABLED` - `NMBS_SERVER_READ_HOLDING_REGISTERS_DISABLED` - `NMBS_SERVER_READ_INPUT_REGISTERS_DISABLED` - `NMBS_SERVER_WRITE_SINGLE_COIL_DISABLED` - `NMBS_SERVER_WRITE_SINGLE_REGISTER_DISABLED` - `NMBS_SERVER_WRITE_MULTIPLE_COILS_DISABLED` - `NMBS_SERVER_WRITE_MULTIPLE_REGISTERS_DISABLED` - `NMBS_SERVER_READ_FILE_RECORD_DISABLED` - `NMBS_SERVER_WRITE_FILE_RECORD_DISABLED` - `NMBS_SERVER_READ_WRITE_REGISTERS_DISABLED` - `NMBS_SERVER_READ_DEVICE_IDENTIFICATION_DISABLED` - `NMBS_STRERROR_DISABLED` to disable the code that converts `nmbs_error`s to strings - Debug prints about received and sent messages can be enabled by defining `NMBS_DEBUG` ", Assign "at most 3 tags" to the expected json: {"id":"13560","tags":[]} "only from the tags list I provide: [{"id":77,"name":"3d"},{"id":89,"name":"agent"},{"id":17,"name":"ai"},{"id":54,"name":"algorithm"},{"id":24,"name":"api"},{"id":44,"name":"authentication"},{"id":3,"name":"aws"},{"id":27,"name":"backend"},{"id":60,"name":"benchmark"},{"id":72,"name":"best-practices"},{"id":39,"name":"bitcoin"},{"id":37,"name":"blockchain"},{"id":1,"name":"blog"},{"id":45,"name":"bundler"},{"id":58,"name":"cache"},{"id":21,"name":"chat"},{"id":49,"name":"cicd"},{"id":4,"name":"cli"},{"id":64,"name":"cloud-native"},{"id":48,"name":"cms"},{"id":61,"name":"compiler"},{"id":68,"name":"containerization"},{"id":92,"name":"crm"},{"id":34,"name":"data"},{"id":47,"name":"database"},{"id":8,"name":"declarative-gui "},{"id":9,"name":"deploy-tool"},{"id":53,"name":"desktop-app"},{"id":6,"name":"dev-exp-lib"},{"id":59,"name":"dev-tool"},{"id":13,"name":"ecommerce"},{"id":26,"name":"editor"},{"id":66,"name":"emulator"},{"id":62,"name":"filesystem"},{"id":80,"name":"finance"},{"id":15,"name":"firmware"},{"id":73,"name":"for-fun"},{"id":2,"name":"framework"},{"id":11,"name":"frontend"},{"id":22,"name":"game"},{"id":81,"name":"game-engine "},{"id":23,"name":"graphql"},{"id":84,"name":"gui"},{"id":91,"name":"http"},{"id":5,"name":"http-client"},{"id":51,"name":"iac"},{"id":30,"name":"ide"},{"id":78,"name":"iot"},{"id":40,"name":"json"},{"id":83,"name":"julian"},{"id":38,"name":"k8s"},{"id":31,"name":"language"},{"id":10,"name":"learning-resource"},{"id":33,"name":"lib"},{"id":41,"name":"linter"},{"id":28,"name":"lms"},{"id":16,"name":"logging"},{"id":76,"name":"low-code"},{"id":90,"name":"message-queue"},{"id":42,"name":"mobile-app"},{"id":18,"name":"monitoring"},{"id":36,"name":"networking"},{"id":7,"name":"node-version"},{"id":55,"name":"nosql"},{"id":57,"name":"observability"},{"id":46,"name":"orm"},{"id":52,"name":"os"},{"id":14,"name":"parser"},{"id":74,"name":"react"},{"id":82,"name":"real-time"},{"id":56,"name":"robot"},{"id":65,"name":"runtime"},{"id":32,"name":"sdk"},{"id":71,"name":"search"},{"id":63,"name":"secrets"},{"id":25,"name":"security"},{"id":85,"name":"server"},{"id":86,"name":"serverless"},{"id":70,"name":"storage"},{"id":75,"name":"system-design"},{"id":79,"name":"terminal"},{"id":29,"name":"testing"},{"id":12,"name":"ui"},{"id":50,"name":"ux"},{"id":88,"name":"video"},{"id":20,"name":"web-app"},{"id":35,"name":"web-server"},{"id":43,"name":"webassembly"},{"id":69,"name":"workflow"},{"id":87,"name":"yaml"}]" returns me the "expected json"