ESP8266 Lua/NodeMCU module for MAX44009 irradiance sensors

This repository contains an ESP8266 NodeMCU Lua module (max44009.lua) as well as MQTT / HomeAssistant / InfluxDB integration example (init.lua) for MAX44009 illuminance sensors connected via I²C.

Dependencies

max44009.lua has been tested with Lua 5.1 on NodeMCU firmware 3.0.1 (Release 202112300746, float build). It requires the following modules.

• bit
• i2c

Most practical applications (such as the example in init.lua) also need the following modules.

• gpio
• mqtt
• node
• tmr
• wifi

Setup

Connect the MAX44009 sensor to your ESP8266/NodeMCU board as follows.

• MAX44009 GND → ESP8266/NodeMCU GND
• MAX44009 VCC → ESP8266/NodeMCU 3V3
• MAX44009 SDA → NodeMCU D1 (ESP8266 GPIO5)
• MAX44009 SCL → NodeMCU D2 (ESP8266 GPIO4)

If you use different pins for SCL and SDA, you need to adjust the i2c.setup call in the examples provided in this repository to reflect those changes. Keep in mind that some ESP8266 pins must have well-defined logic levels at boot time and may therefore be unsuitable for MAX44009 connection.

Usage

Copy max44009.lua to your NodeMCU board and set it up as follows.

max44009 = require("max44009")
i2c.setup(0, 1, 2, i2c.SLOW)

-- can be called with up to 10 Hz
function some_timer_callback()
    local lx = max44009.read()
    if lx ~= nil then
        -- lx : Illuminance as floating point value [lx]
    else
        print("MAX44009 error")
    end
end

Application Example

init.lua is an example application with HomeAssistant integration. To use it, you need to create a config.lua file with WiFI and MQTT settings:

station_cfg = {ssid = "...", pwd = "..."}
mqtt_host = "..."

Optionally, it can also publish readings to InfluxDB. To do so, configure URL and attribute:

influx_url = "..."
influx_attr = "..."

Readings will be published as max44009[influx_attr] illuminance_lx=%f. So, unless influx_attr = '', it must start with a comma, e.g. influx_attr = ',device=' .. device_id.