Wifi temperature / humidity sensor for under £20 with an OLED display
So I wanted a display output for the wifi temp modules, so I bought a few of these: http://www.ebay.co.uk/itm/111474769297?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
which are 128x64 displays with an i2c interface.It uses a multi-master protocol and has 2 x i2c lines which are SDA (serial data) and SCL (serial clock).
The reason for these, is that they use less power than a traditional LCD, have persistence when powering them, and are brighter than LCDs.
Code wise, I separated it into main code and a init loader (init being the first code loaded when the esp boots).
This basically
Loader:
gpio.mode(1,gpio.OUTPUT)
gpio.write(1,gpio.HIGH)
wifi.setmode(wifi.STATION)
wifi.sta.config("wifi name","wifi passwd")
print (wifi.sta.getip())
gpio.write(1,gpio.LOW)
dofile("main.lua")
Main.lua
print("Running main")The code above requires dht22.lc to be loaded ( from here ), which should be compiled on the ESP2866, once uploaded as a LUA.
gpio.mode(2,gpio.OUTPUT)
BLUE=1
gpio.mode(BLUE,gpio.OUTPUT)
gpio.write(BLUE,gpio.HIGH)
-- Set the LED to flash
pwm.stop(2)
pwm.setup(2,1,10)
pwm.start(2)
-- Load library
sda_pin = 5
scl_pin = 6
dht_pin = 4
oled_addr = 0x3c
-- Counter for heartbeat
cnt = 1
state = 0
-- global for display/read dht
humidtwo = 0
temptwo = 0
-- Heap limit
heap_limit= 22000
function init_OLED(sda,scl)
sla = 0x3c
i2c.setup(0, sda, scl, i2c.SLOW)
disp = u8g.ssd1306_128x64_i2c(sla)
disp:setFont(u8g.font_6x12)
disp:setFontRefHeightExtendedText()
disp:setDefaultForegroundColor()
disp:setFontPosTop()
end
function read_sensor_values()
local varh,vart
dht22.read(dht_pin)
varh = dht22.getHumidity()
vart = dht22.getTemperature()
if varh ~= nil then
humidtwo = (varh/10).."."..(varh%10)
else
print ("Previous H : " ..humidtwo)
end
if vart ~= nil then
temptwo = (vart/10).."."..(vart%10)
else
print ("Previous T : " ..temptwo)
end
end
function display_sensor_values(vvar)
disp:firstPage()
disp:setFont(u8g.font_6x10)
disp:setFontRefHeightExtendedText()
disp:setDefaultForegroundColor()
disp:setFontPosTop()
local x,y,ip,nm,st,deg,result
if state==1 then
st=string.char(176)
else
st=" "
end
deg=string.char(176)
repeat
disp:drawRFrame(0, 0, 128-1, 64-1, 1)
x=4
y=8
disp:drawStr(x, y, 'T:' .. (temptwo) .. deg ..'C H:' .. (humidtwo) .. '%RH' )
y = y+14
disp:drawStr(x, y, st .. ' H:' .. (node.heap()) .. ' C:' .. (cnt) )
y = y+14
if wifi.sta.status()==0 then result='STA_IDLE' end
if wifi.sta.status()==1 then node.restart() end
if wifi.sta.status()==2 then result='STA_WRONG PASSWD' end
if wifi.sta.status()==3 then result='STA_NO AP FOUND' end
if wifi.sta.status()==4 then result='STA_CONNECT FAILED' end
if wifi.sta.status()==5 then result='STA_GOT_IP' end
if vvar==1 then
ssid,password,bssid_set,bssid=wifi.sta.getconfig()
result= ssid
ssid,password,bssid_set,bssid=nil,nil,nil,nil
end
disp:drawStr(x, y, result )
y = y+14
ip,nm=wifi.sta.getip()
if ip ~= nil then
disp:drawStr(x, y, 'IP:' .. (ip) )
else
disp:drawStr(x, y, 'IP: Cannot get IP')
node.restart()
end
until disp:nextPage() == false
cnt = cnt + 1
if cnt > 999 then
cnt=1
end
end
init_OLED(5,6)
i2c.setup(0, sda_pin, scl_pin, i2c.SLOW)
disp = u8g.ssd1306_128x64_i2c(oled_addr)
sv=net.createServer(net.TCP, 2)
sv:listen(80,function(c)
c:on("receive", function(c, pl)
print(pl)
if pl=="1" then
print ("gpio1 low")
gpio.write(1,gpio.LOW)
end
if pl=="2" then
print ("gpio1 high")
gpio.write(1,gpio.HIGH)
end
end)
dht22 = require("dht22")
gpio.mode(BLUE,gpio.OUTPUT)
gpio.write(BLUE,gpio.HIGH)
read_sensor_values()
display_sensor_values()
dht22=nil
print("Humidity: "..humidtwo.." %")
print("Temperature: "..temptwo.." deg C")
c:send("H:"..humidtwo.." ; T:"..temptwo.."\r\n")
c:close()
gpio.write(BLUE,gpio.LOW)
hp=node.heap()
if hp<5000 then
node.restart()
end
collectgarbage()
end)
tmr.alarm( 2, 1000, 1, function()
if state == 0 then
display_sensor_values(1)
end
if state == 1 then
display_sensor_values(0)
end
state = (state + 1) %2
collectgarbage()
end)
Doing a list should show something like this:
dht22.lc : 1308 bytesThe OLED display should be like so:
init.lua : 199 bytes
main.lc : 4176 bytes
main.lua : 3521 bytes
T: 25.3oC H: 26.9%RH
* H:22824 C:288
STA_GOT_IP
IP: 10.10.0.164
So with this it will display the (T:) temperature in the top left, with the humidity level (H:) in the top right.
The next line shows a heartbeat icon, followed by heap size in bytes (H:).
I've programmed this so that if the heap space get below 5000 bytes, it will restart itself.
C: is the count, and when it reaches 999, it will go back to 1. This is purely to show it's doing some processing.
The next line alternates between the wifi status codes and the actual SSID it's connected to. This alternates every second.
The last line (IP:) shows the ip currently assigned to the device.
My output to RRD graph is something like this:
The drop outs are caused by the wifi signal (or lack of).
Part 1 here
