Control Your RC Car With Your Android Tablet

-------------------------------
-- wifi hot spot config
wifi.setmode(wifi.SOFTAP)
cfg={}
cfg.ssid="mywifi"
cfg.pwd="qwerty123"
cfg.ip="192.168.0.1"
cfg.netmask="255.255.255.0"
cfg.gateway="192.168.0.1"
port = 9876
wifi.ap.setip(cfg)
wifi.ap.config(cfg) 
-------------------------------
  
function stringStarts(a,b)
    return string.sub(a,1,string.len(b))==b
end

function stringEnds(a,b)
   return b=='' or string.sub(a,-string.len(b))==b
end

-------------------------------
-- servo config
servo = {}
servo.pin = 2 --this is GPIO0
servo.value = 75
servo.id = "servo"
-------------------------------

-------------------------------
-- ESC config
esc = {}
esc.pin = 3 --this is GPIO0
esc.value = 75
esc.id = "esc"
-------------------------------

-------------------------------
-- LEDs config
ledcon = {}
ledcon.pin = 1 --this is GPIO0

ledon = {}
ledon.pin = 4
-------------------------------

cmd = ""

-------------------------------
-- PWM setup 50 Hz for servo and ESC
pwm.setup(servo.pin, 50, servo.value) 
pwm.start(servo.pin)
pwm.setup(esc.pin, 50, esc.value) 
pwm.start(esc.pin)
-------------------------------

-------------------------------
-- LEDs setup
gpio.mode(ledcon.pin,gpio.OUTPUT)
gpio.mode(ledon.pin,gpio.OUTPUT)
gpio.write(ledon.pin,gpio.HIGH)
-------------------------------

function exeCmd(st)
    if stringStarts(st, servo.id.." ") then -- value comes after id + space
        -- servo command
        servo.value = tonumber( string.sub(st,1+string.len(servo.id.." "),string.len(st)) )
        pwm.setduty(servo.pin, servo.value)
    elseif stringStarts(st, esc.id.." ") then -- value comes after id + space
    	-- ESC command
        esc.value = tonumber( string.sub(st,1+string.len(esc.id.." "),string.len(st)) )
        pwm.setduty(esc.pin, esc.value)
    end    
end

-------------------------------
-- Analyse the TCP frame
function receiveData(conn, data)
    cmd = cmd .. data

    local a, b = string.find(cmd, "\n", 1, true)   
    while a do
        exeCmd( string.sub(cmd, 1, a-1) )
        cmd = string.sub(cmd, a+1, string.len(cmd))
        a, b = string.find(cmd, "\n", 1, true)
    end 
end

-------------------------------
-- TCP server creation
srv=net.createServer(net.TCP, 28800) 
srv:listen(port,function(conn)
    gpio.write(ledcon.pin,gpio.HIGH)
    conn:send("dbg connected ok\n")
     
    conn:on("receive",receiveData)  
    
    conn:on("disconnection",function(c) 
        gpio.write(ledcon.pin,gpio.LOW)
    end)
    
end)