Connect to and update arduino over wifi with esp8266

init.lua

-- Code to connect to or update an arduino over wifi with an esp8266 (nodemcu lua firmware)
-- Send a single 'B' char to switch the connection to update mode
-- echo -n 'B' | nc 192.168.178.57 8080 ; avrdude -v -p atmega328p -c arduino -P net:192.168.178.57:8080 -D -U flash:w:code.hex:i

-- there are more instructions to come, but thats it for now

-- because there is no way of reaching the esp repl with this code running, there is an override.
-- currently it delays the startup for 2 secs. In that timeframe you should pull the overridepin to GND to stop booting into redirect mode

-- just using one gpio for triggering reset on the arduino and overriding the boot sequence into redirect mode of the esp

-- this code is still WIP
-- will add some wiring instructions soonisch, basicly just connect the uart to the arduino uart pins, the resetpin to the conficured gpio


resetPin=4
overridePin=4

gpio.mode(overridePin, gpio.INPUT)

bootloadermode=false

ssid='xxxxx'
pass='xxxxx'

function startServer()
  sv=net.createServer(net.TCP, 180)
  sv:listen(8080,   function(conn)
    -- wifi console connected
    local newConn=true

    if(bootloadermode) then
      gpio.write(resetPin, gpio.LOW)
      tmr.delay(10000)
      gpio.write(resetPin, gpio.HIGH)
    end

    function s_output(str)
      if (conn~=nil)    then
        conn:send(str)
      end
    end

    --redirect node core stuff
    node.output(s_output,0)

    --redirect uart stuff
    uart.on("data", 1, s_output, 0)

    conn:on("receive", function(conn, pl) 
      --node.input(pl)
      if(newConn and pl == "B") then
        bootloadermode=true
        s_output('bootloadermode')
        pl = 'bootloadermode'
      else
         bootloadermode=false
      end
      newConn=false

      uart.write(0, pl)
      if (conn==nil)  then
        node.output(nil)
        uart.on("data")
      end
    end)

    conn:on("disconnection",function(conn) 
      node.output(nil)
      uart.on("data")
    end)
  end)   
end

function startRedirector()
  gpio.mode(resetPin, gpio.OUTPUT)
  gpio.write(resetPin, gpio.LOW)

  wifi.setmode(wifi.STATION)
  wifi.sta.config(ssid,pass)
  wifi.sta.connect()

  tmr.alarm(0, 1000, 1, function() 
    if wifi.sta.getip()=="0.0.0.0" then
      --print("Connect AP, Waiting...") 
    else
      startServer()
      tmr.stop(0)
      uart.setup( 0, 57600, 8, 0, 1, 0 )
      gpio.write(resetPin, gpio.HIGH)
    end
  end)
end

print("READING PIN " .. overridePin .. " FOR 2 SEC TO OVERRIDE STARTUP")

tmr.alarm(0, 2000, 1, function() 
  tmr.stop(0)

  if(gpio.read(overridePin) == 1) then
    ---BOOTING only if overridePin is HIGH
    print("BOOTING UART REDIRECT. PIN " .. overridePin .. " IS HIGH")

    startRedirector()
  else
    print("OVERRIDING BOOT. PIN " .. overridePin .. " IS LOW")
  end
end)