co2.rb

#!/usr/bin/env ruby 

require 'serialport'

class MH_Z19
	STARTING_BYTE = 0xff
	CMD_GAS_CONCENTRATION = 0x86
	CMD_CALIBRATE_ZERO_POINT = 0x87
	CMD_CALIBRATE_SPAN_POINT = 0x88

	class GenericException < Exception; end
	class InvalidPacketException < GenericException; end

	def initialize(io, sensor_id: 0x01)
		if io.is_a? String
			@io = SerialPort.new(
				io,
				9600,
				8,
				1,
				0
			)
			@io.flow_control = SerialPort::NONE
			@io.set_encoding(Encoding::BINARY)
		else
			@io = io
		end
		@sensor_id = sensor_id
	end

	def close
		@io.close
	end

	def gas_concentration
		packet = Array.new(9) { 0 }
		packet[0] = STARTING_BYTE
		packet[1] = @sensor_id
		packet[2] = CMD_GAS_CONCENTRATION
		packet[8] = checksum(packet)

		@io.write packet.pack("C*")
		raw_packet = @io.read(9)
		raise InvalidPacketException, "packet seems nil" if raw_packet.nil?

		packet = raw_packet.unpack("C*")
		sum = checksum(packet)
		unless packet[8] == sum
			raise InvalidPacketException, "packet checksum is invalid"
		end
		
		(packet[2] << 8) | packet[3]
	end

	def calibrate_zero_point
		packet = Array.new(9) { 0 }
		packet[0] = STARTING_BYTE
		packet[1] = @sensor_id
		packet[2] = CMD_CALIBRATE_ZERO_POINT
		packet[8] = checksum(packet)
		@io.write packet.pack("C*")
		# no return value
		nil
	end

	def calibrate_span_point(span_point)
		packed = [span_point].pack("n")

		packet = Array.new(9) { 0 }
		packet[0] = STARTING_BYTE
		packet[1] = @sensor_id
		packet[2] = CMD_CALIBRATE_SPAN_POINT
		packet[3] = packet[0]
		packet[4] = packet[1]
		packet[8] = checksum(packet)
		@io.write packet.pack("C*")
		# no return value
		nil
	end

	private
	def checksum(packet)
		raise InvalidPacketException, "invalid packet size" unless packet.size == 9
		sum = 0
		(1...8).each do |i|
			sum = (sum + packet[i]) & 0xff
		end
		sum = 0xff - sum
		sum += 1
		sum
	end
end

if ENV['PORT'].nil?
	require 'socket'
	s1, s2 = Socket.pair(:UNIX, :STREAM, 0)
	Thread.start do
		Thread.abort_on_exception = true
		while packet = s2.read(9)
			case packet
			when "\xFF\x01\x86\x00\x00\x00\x00\x00y".b
				ret = "\xFF\x86\x02\x60\x47\x00\x00\x00\xd1"
				s2.write(ret)
			else
				raise "unknown packet #{packet.inspect}"
			end
		end
	end

	co2 = MH_Z19.new(s1)
	p co2.gas_concentration
end


require 'net/http'
require 'uri'

uri = URI(ENV['GF_URI']) rescue nil

co2 = MH_Z19.new(ENV['PORT'])
loop do
	begin
		ppm = co2.gas_concentration
		p ppm
		unless uri.nil?
			res = Net::HTTP.post_form(uri, 'number' => ppm)
			p res
		end
	rescue => e
		p e
		puts e.backtrace
	end
	sleep 1
end