From f6d4dcb42da4901944da1bc5d96c9ec6fbfbe134 Mon Sep 17 00:00:00 2001
From: Daniel Friesel <derf@finalrewind.org>
Date: Fri, 29 Apr 2022 19:40:02 +0200
Subject: average ten PM2.5 readings before reporting to HASS

---
 init.lua | 33 ++++++++++++++++++++++-----------
 1 file changed, 22 insertions(+), 11 deletions(-)

diff --git a/init.lua b/init.lua
index a6335fc..f5b19ee 100644
--- a/init.lua
+++ b/init.lua
@@ -7,7 +7,6 @@ device_id = "esp8266_" .. chip_id
 mqtt_prefix = "sensor/" .. device_id
 mqttclient = mqtt.Client(device_id, 120)
 
-
 print("ESP8266 " .. chip_id)
 
 ledpin = 4
@@ -16,6 +15,8 @@ gpio.write(ledpin, 0)
 
 pm1006 = require("pm1006")
 
+pm_values = {}
+
 function log_restart()
 	print("Network error " .. wifi.sta.status() .. ". Restarting in 20 seconds.")
 	delayed_restart:start()
@@ -58,22 +59,32 @@ function uart_callback(data)
 		print("Invalid PM1006 frame")
 		return
 	else
-		local json_str = string.format('{"pm2_5_ugm3": %d, "rssi_dbm": %d}', pm2_5, wifi.sta.getrssi())
-		if not publishing then
-			publishing = true
-			gpio.write(ledpin, 0)
-			mqttclient:publish(mqtt_prefix .. "/data", json_str, 0, 0, function(client)
-				publishing = false
-				gpio.write(ledpin, 1)
-				collectgarbage()
-			end)
+		table.insert(pm_values, pm2_5)
+		if table.getn(pm_values) == 10 then
+			local pm_sum = 0
+			for i, pm_value in ipairs(pm_values) do
+				pm_sum = pm_sum + pm_value
+			end
+			local pm_int = pm_sum / 10
+			local pm_frac = pm_sum % 10
+			local json_str = string.format('{"pm2_5_ugm3": %d.%d, "rssi_dbm": %d}', pm_int, pm_frac, wifi.sta.getrssi())
+			pm_values = {}
+			if not publishing then
+				publishing = true
+				gpio.write(ledpin, 0)
+				mqttclient:publish(mqtt_prefix .. "/data", json_str, 0, 0, function(client)
+					publishing = false
+					gpio.write(ledpin, 1)
+					collectgarbage()
+				end)
+			end
 		end
 	end
 end
 
 function hass_register()
 	local hass_device = string.format('{"connections":[["mac","%s"]],"identifiers":["%s"],"model":"ESP8266 + PM1006","name":"Vindriktning %s","manufacturer":"derf"}', wifi.sta.getmac(), device_id, chip_id)
-	local hass_entity_base = string.format('"device":%s,"state_topic":"%s/data","expire_after":60', hass_device, mqtt_prefix)
+	local hass_entity_base = string.format('"device":%s,"state_topic":"%s/data","expire_after":90', hass_device, mqtt_prefix)
 	local hass_pm2_5 = string.format('{%s,"name":"PM2.5","object_id":"%s_pm2_5","unique_id":"%s_pm2_5","device_class":"pm25","unit_of_measurement":"µg/m³","value_template":"{{value_json.pm2_5_ugm3}}"}', hass_entity_base, device_id, device_id)
 	local hass_rssi = string.format('{%s,"name":"RSSI","object_id":"%s_rssi","unique_id":"%s_rssi","device_class":"signal_strength","unit_of_measurement":"dBm","value_template":"{{value_json.rssi_dbm}}","entity_category":"diagnostic"}', hass_entity_base, device_id, device_id)
 
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