Unverified Commit 102dd007 authored by Daniel Friesel's avatar Daniel Friesel
Browse files

verify checksum, parse automatic baseline correction data

parent ee6a1033

README.md

+4 −4
Original line number Diff line number Diff line
@@ -41,17 +41,17 @@ levels at boot time and may therefore be unsuitable for MH-Z19 connection. 
Copy **mh-z19.lua** to your NodeMCU board and set it up as follows.



```lua

mhz19 = require("mh-z19")

mh_z19 = require("mh-z19")

port = softuart.setup(9600, 1, 2)

port:on("data", 9, uart_callback)



function uart_callback(data)

	if sds011.parse_frame(data) then

		-- mhz19.co2 contains the CO₂ concentration in ppm

	if mh_z19.parse_frame(data) then

		-- mh_z19.co2 contains the CO₂ concentration in ppm

	end

end



port:write(mhz19.query())

port:write(mhz19.c_query)

```



## Application Example

init.lua

+5 −5
Original line number Diff line number Diff line
@@ -16,7 +16,7 @@ ledpin = 4 
gpio.mode(ledpin, gpio.OUTPUT)

gpio.write(ledpin, 0)



mhz19 = require("mh-z19")

mh_z19 = require("mh-z19")



poll = tmr.create()
@@ -58,13 +58,13 @@ function connect_wifi() 
end



function uart_callback(data)

	if not mhz19.parse_frame(data) then

	if not mh_z19.parse_frame(data) then

		print("Invalid MH-Z19 frame")

		return

	end



	local json_str = string.format('{"rssi_dbm":%d,"co2_ppm":"%d"}', wifi.sta.getrssi(), mhz19.co2)

	local influx_str = string.format("co2_ppm=%d", mhz19.co2)

	local json_str = string.format('{"rssi_dbm":%d,"co2_ppm":"%d"}', wifi.sta.getrssi(), mh_z19.co2)

	local influx_str = string.format("co2_ppm=%d", mh_z19.co2)



	if not publishing_mqtt then

		watchdog:start(true)
@@ -94,7 +94,7 @@ function publish_influx(payload) 
end



function query_data()

	port:write(mhz19.query())

	port:write(mh_z19.c_query)

end



function hass_register()

mh-z19.lua

+19 −18
Original line number Diff line number Diff line 
local mhz19 = {}

local mh_z19 = {}



local c_read = string.char(0xff, 0x01, 0x86, 0x00, 0x00, 0x00, 0x00, 0x00, 0x79)

mh_z19.c_query = string.char(0xff, 0x01, 0x86, 0x00, 0x00, 0x00, 0x00, 0x00, 0x79)



mhz19.co2 = nil

mhz19.temp = nil

mhz19.tt = nil

mhz19.ss = nil

mhz19.uu = nil

mh_z19.co2 = nil

mh_z19.temp = nil

mh_z19.abc_count = nil

mh_z19.abc_ticks = nil



function mhz19.query()

	return c_read

function checksum(b1, b2, b3, b4, b5, b6, b7)

	return 0xff - ((b1 + b2 + b3 + b4 + b5 + b6 + b7) % 0x100) + 1

end



function mhz19.parse_frame(data)

	local head, cmd, co2h, co2l, temp, tt, ss, uh, ul = struct.unpack("BBBBBBBBB", data)

	if head ~= 0xff or cmd ~= 0x86 then

function mh_z19.parse_frame(data)

	local start, cmd, co2h, co2l, temp, u1, abc_ticks, abc_count, cksum = struct.unpack("BBBBBBBBB", data)

	if start ~= 0xff or cmd ~= 0x86 then

		return false

	end

	mhz19.co2 = co2h * 256 + co2l

	mhz19.temp = temp - 40

	mhz19.tt = tt

	mhz19.ss = ss

	mhz19.uu = uh * 256 + ul

	if checksum(cmd, co2h, co2l, temp, u1, abc_ticks, abc_count) ~= cksum then

		return false

	end

	mh_z19.co2 = co2h * 256 + co2l

	mh_z19.temp = temp - 40

	mh_z19.abc_ticks = abc_ticks

	mh_z19.abc_count = abc_count

	return true

end



return mhz19
 
return mh_z19