button.c

#include <stdio.h>
#include <stdlib.h>
#include "button.h"

struct libusb_device_handle *openButton()
{
	libusb_context *ctx = NULL;

	if (libusb_init(&ctx) != 0) {
		fprintf(stderr, "Cannot init libusb!\n");
		return NULL;
	}

	/* Find the Dream Cheeky Big Red Button */
	struct libusb_device_handle *hDev = libusb_open_device_with_vid_pid(ctx, 0x1d34, 0xd);

	if (hDev == NULL) {
		fprintf(stderr, "Cannot access the button! Is it connected?\n");
		return NULL;
	}

	if (libusb_kernel_driver_active(hDev, 0) == 1) {
		if (libusb_detach_kernel_driver(hDev, 0) != 0) {
			fprintf(stderr, "Device is busy. :(\n");
			return NULL;
		}
	}

	int result = libusb_claim_interface(hDev, 0);

	if (result < 0) {
		fprintf(stderr, "Cannot claim the button - Error code is %i\n", result);
		return NULL;
	}

	return hDev;
}

unsigned char getButtonState(struct libusb_device_handle *dev) {
	if (libusb_control_transfer(
	                            dev,
	                            CONTROL_REQUEST_TYPE_IN, HID_SET_REPORT,
	                            (HID_REPORT_TYPE_OUTPUT<<8),
	                            0,
	                            HID_CTRL_DATA,
	                            8,
	                            500
                                   ) < 0) {
		fprintf(stderr, "Cannot write to the button.\n");
		return 0;
	}

	int bytesRead=0;
	char buffer[8];
	int result = libusb_interrupt_transfer(dev, 0x81, buffer, 8, &bytesRead, 500);

	if (result < 0) {
		fprintf(stderr, "Failed to read from button.\n");
		return 0;
	}

	return buffer[0];
}