Demonstrate Mac hidapi bug sending to Teensy doing RawHID sketch: https://www.pjrc.com/teensy/rawhid.html

test-rawhid.c

// test-rawhid.c -- Demonstrate writing to Teensy running RawHID sketch
//                  On Mac, this will occasionally hang in hid_write()
//
// Build with:
// gcc -I ../hidapi/hidapi -framework IOKit -framework CoreFoundation../hidapi/mac/hid.c rawhid-test.c
//
// Tod E. Kurt / github.com/todbot
//

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "hidapi.h"

void printbuf(char* buf, int bufsize) {
    printf("buf:");
    for (int i = 0; i < bufsize; i++) {
        printf("%d,", buf[i]);
    }
    printf("\n");
}

int main(int argc, char* argv[])
{
	int res;
	unsigned char buf[64];
	#define MAX_STR 255
	wchar_t wstr[MAX_STR];
	hid_device *handle;
	int i;

	// Enumerate and print the HID devices on the system
	struct hid_device_info *devs, *cur_dev;
    char foundpath[1024]; // 1024 should be enough for anyone :)

	devs = hid_enumerate(0x0, 0x0);
	cur_dev = devs;
	while (cur_dev) {
		printf("Device: vid/pid: %04hx/%04hx\n  path: %s\n  serial_number: %ls usage_page: %x, usage: %x",
			cur_dev->vendor_id, cur_dev->product_id, cur_dev->path, cur_dev->serial_number, cur_dev->usage_page, cur_dev->usage);
		printf("\n");
		printf("  Manufacturer: %ls\n", cur_dev->manufacturer_string);
		printf("  Product:      %ls\n", cur_dev->product_string);
		printf("\n");
        if( cur_dev->vendor_id == 0x16C0 && cur_dev->product_id == 0x0486 && cur_dev->usage_page == 0xFFAB && cur_dev->usage == 0x200 ) {
            printf("Found our device!\n");
            strcpy( foundpath, cur_dev->path );
        }
		cur_dev = cur_dev->next;
	}
	hid_free_enumeration(devs);


	// Open the device using the VID, PID,
	// and optionally the Serial number.
	// handle = hid_open(0x16C0, 0x0486, NULL);
	handle = hid_open_path( foundpath );

    memset(buf, 0, sizeof(buf));
    buf[0] = 'x';
    buf[1] = 'y';
    buf[2] = 'z';
    printbuf((char*)buf, sizeof(buf));

    res = hid_write(handle, buf, sizeof(buf));
    if (res < 0) {
        printf("unable to write()");
    }

//#define ENABLE_READ
#ifdef ENABLE_READ
    // Read requested state
	res = hid_read(handle, buf, sizeof(buf));
	if (res < 0) {
		printf("Unable to read()\n");
    }
    else {
        // Print out the returned buffer.
        printbuf( (char*)buf, res);
    }
#endif
	return 0;
}