libusb 1.0 implementation with C language. It is used to write the instruction to change Mouse Logitech G102/G203 RGB color.

logitech_g102.c

#include <libusb-1.0/libusb.h>
#include <stdio.h>
#include <stdlib.h>

#define VID  0x046d
#define PRID 0xc084

/**
 * Sending solid RGB color bytes to Logitech G102 / G203.
 * LIBRARY: -lusb-1.0
 * 
 * NOTE: Bytes has been transferred but the LED could not recognize it.
 * @author KennFatt https://kennan.xyz/
 */
int main(int argc, char **argv) {
    libusb_context *ctx = NULL;
    libusb_device *dev = NULL;
    libusb_device_handle *dh = NULL;
    int wIndex = 0x00;

    int err = libusb_init(&ctx);
    if (err != 0) {
        printf("Error when initialize libusb: %d\n", err);
        return EXIT_FAILURE;
    }

    dh = libusb_open_device_with_vid_pid(ctx, VID, PRID);
    if (dh == NULL) {
        printf("Could not open device with VendorId: %d, ProductId: %d\n", VID,
               PRID);
        return EXIT_FAILURE;
    }

    // attach device
    dev = libusb_get_device(dh);
    if (dev == NULL) {
        printf("Could not find device with given device handler!\n");
        return EXIT_FAILURE;
    }
    wIndex = 0x01;
    if (libusb_kernel_driver_active(dh, wIndex)) {
        printf("Kernel driver active!\n");
        int det_status = libusb_detach_kernel_driver(dh, wIndex);
        if (det_status != 0) {
            printf("Could not detach the kernel driver: %d\n", det_status);
            return EXIT_FAILURE;
        }
        int claim_status = libusb_claim_interface(dh, wIndex);
        if (claim_status != 0) {
            printf("Could not claim the device! %d\n", claim_status);
            return EXIT_FAILURE;
        }
    }

    // parse bytes
    const char *raw_bytes = "11ff0e3b0001ff00ff0000000000";
    const char *offset = raw_bytes;
    unsigned char payload[14];
    for (unsigned i = 0; i < 14; ++i, offset += 2) {
        char buff[5] = {0x30, 0x78, offset[0], offset[1], 0};
        payload[i] = strtol(buff, NULL, 0);
    }

    int status = libusb_control_transfer(dh, 0x21, 0x09, 0x0211, wIndex,
                                         payload, 0x0e, 1000);
    printf("Status: %d\n", status);

    // Detach
    if (wIndex != 0x00) {
        int rel_status = libusb_release_interface(dh, wIndex);
        if (rel_status != 0) {
            printf("Could not release interface: %d\n", rel_status);
            return EXIT_FAILURE;
        }

        int att_status = libusb_attach_kernel_driver(dh, wIndex);
        if (att_status != 0) {
            printf("Could not attach kernel driver: %d\n", att_status);
            return EXIT_FAILURE;
        }
    }

    libusb_exit(ctx);
    return EXIT_SUCCESS;
}