01teensy.ino

#include "usb_dev.h"

const int pinLED = 13;

void setup() {
  pinMode(pinLED, OUTPUT);

  usb_init();

  while (usb_configuration == 0) {
    delay(5000);
    digitalWrite(pinLED, HIGH);
    delay(5000);
    digitalWrite(pinLED, LOW);
  }
  
  digitalWrite(pinLED, LOW);
}

void loop() {
  uint8_t buffer[64] = { 0 };
  
  usb_rawhid_recv(&buffer, 10000);

  for (int i = 0; i < 64; i++) {
    if (buffer[i] > 0) {
      // Short flashes signal "receieved"
      digitalWrite(pinLED, HIGH);
      delay(100);
      digitalWrite(pinLED, LOW);
      delay(100);
      digitalWrite(pinLED, HIGH);
      delay(100);
      digitalWrite(pinLED, LOW);
      delay(100);
      digitalWrite(pinLED, HIGH);
      delay(100);
      digitalWrite(pinLED, LOW);
      break;
    }
  }

  // Long flash is "waiting"
  digitalWrite(pinLED, HIGH);
  delay(1000);
  digitalWrite(pinLED, LOW);
}

02write.c

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

#include <sys/ioctl.h>
#include <termios.h>

#include "hid.h"

int main() {
    uint8_t buf[64];
    int r = rawhid_open(1, 0x16C0, 0x0486, 0xFFAB, 0x0200);
    if (r <= 0) {
        printf("No rawhid device found!\n");
    } else {
        printf("Found rawhid device...\n");
    }
    printf("Sending...\n");
    buf[0] = 0x01;
    for (int i = 1; i < 64; i++) {
        buf[i] = 0x01;
    }
    int result = rawhid_send(0, buf, 64, 100);
    printf("Got rawhid_send result: %d\n", result);
}

03Makefile

OS = MACOSX

PROG = rawhid_test
TARGET = $(PROG)
SDK = /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk
ARCH = -mmacosx-version-min=10.12
CC = gcc
STRIP = strip
CFLAGS = -Wall -O0 -DOS_$(OS) -isysroot $(SDK) $(ARCH)
LIBS = $(ARCH) -Wl,-syslibroot,$(SDK) -framework IOKit -framework CoreFoundation
OBJS = $(PROG).o hid.o

all: $(TARGET)

$(PROG): $(OBJS)
	$(CC) -o $(PROG) $(OBJS) $(LIBS)
	$(STRIP) $(PROG)

hid.o: hid_$(OS).c hid.h
	$(CC) $(CFLAGS) -c -o $@ $<

clean:
	rm -f *.o $(PROG) $(PROG).exe $(PROG).dmg
	rm -rf tmp

04write.js

// Write to Teensy rawhid from Node.js
const hid = require('node-hid')
var devices = hid.devices().filter(function (eachDevice) {
    return eachDevice.productId == 0x0486 && eachDevice.vendorId == 5824 && eachDevice.usage == 0x0200
})
var device = new hid.HID(devices[0].path)
device.write([0x00, 0x01, 0x01, 0x05, 0xff, 0xff]);