A simple push/pull USB HID API script for raw devices

usb_hid_api_device.rb

#!/usr/bin/env ruby

# rvm use default
#### install for macOS
# \curl -sSL https://get.rvm.io | bash -s stable --ruby
# source $HOME/.rvm/scripts/rvm
# rvm use default
# gem install hidapi

require "hidapi"

STDOUT.sync = true # allow us to use pipes on the output

vendor_id = 0x10c4
product_id = 0x63cd

kext_handle = HIDAPI::SetupTaskHelper.new(
  vendor_id,          # vendor_id
  product_id,         # product_id
  "irradiance",       # simple_name
  0                   # interface
).run

handle = HIDAPI::open(0x10c4, 0x63cd)
# printf "%04X:%04X %02x Mfg: %-12s  P: %s\n", 0x10c4, 0x63cd, 0, handle.get_manufacturer_string, handle.get_product_string
buf = Array.new(61) { |i| (0) };
buf[0] = 0x2

while 1 do
  handle.write(buf)
  rbuf = handle.read_timeout(buf.length,1000)
  print rbuf.read_bytes(buf.length).unpack("C*"), "\n"
  #rbuf.read_bytes(61).unpack("C*") # full packet
  sleep(0.2)
end

HIDAPI::hid_close(handle)

if you want to use the HIDAPI layer via FFI, we need buffers like this:

# ffi hacking https://github.com/ffi/ffi/wiki/Examples

buffer = FFI::Buffer.new(:char, 61)
res = HidApi.hid_read_timeout handle, buffer, 61, 1000

still works 2020. must use rvm on macOS, though.