ESP8266 How To Make Phone Calls (With Voice!) Using Twilio’s API and NodeMcu

Step 1: Create a Twilio Account

Head over to Twilio.com and create a free or paid account. In your account dashboard find your Account SID and Token and save them as will need it in the code.

Step 2: Send a POST Request to IoT HTTPS Relay

IoT HTTPS Relay is a Google App Engine app I created to use HTTPS APIs since the ESP8266 does not support SSL.

To make a call using IoT HTTPS Relay send the following POST request from your ESP8266:

POST /twilio/Calls.json HTTP/1.1
Host: iot-https-relay.appspot.com
Connection: close
Content-Type: application/x-www-form-urlencoded
Content-Length: xxx

token=xxxxxx&From=15558689998&To=19998675584&Body=myURLEncodedMessage&sid=xxxxxx

The token and sid parameters are your Twilio’s Token and Account SID. The From number can only be your Twilio’s given number. The To number can be any number if you are paying for Twilio’s service, or it can be your verified number if you are using the free account. The Body value will be played when the To phone number answers the phone.

Step 3: Use NodeMcu to Make The Call

If your ESP has the NodeMcu firmware installed you can use the following script to make the calls:

-- Your access point's SSID and password
local SSID = "xxxxxx"
local SSID_PASSWORD = "xxxxxxx"

-- configure ESP as a station
wifi.setmode(wifi.STATION)
wifi.sta.config(SSID,SSID_PASSWORD)
wifi.sta.autoconnect(1)

local TWILIO_ACCOUNT_SID = "xxxxxxxxxxxx"
local TWILIO_TOKEN = "xxxxxxxxxxxx"

local HOST = "iot-https-relay.appspot.com"
local URI = "/twilio/Calls.json"

function build_post_request(host, uri, data_table)

     local data = ""
     
     for param,value in pairs(data_table) do
          data = data .. param.."="..value.."&"
     end

     request = "POST "..uri.." HTTP/1.1\r\n"..
     "Host: "..host.."\r\n"..
     "Connection: close\r\n"..
     "Content-Type: application/x-www-form-urlencoded\r\n"..
     "Content-Length: "..string.len(data).."\r\n"..
     "\r\n"..
     data

     print(request)
     
     return request
end

local function display(sck,response)
     print(response)
end

-- When using send_sms: the "from" number HAS to be your twilio number.
-- If you have a free twilio account the "to" number HAS to be your twilio verified number.
local function make_call(from,to,body)

     local data = {
      sid = TWILIO_ACCOUNT_SID,
      token = TWILIO_TOKEN,
      Body = string.gsub(body," ","+"),
      From = from,
      To = to
     }
     
     socket = net.createConnection(net.TCP,0)
     socket:on("receive",display)
     socket:connect(80,HOST)

     socket:on("connection",function(sck) 
       
          local post_request = build_post_request(HOST,URI,data)
          sck:send(post_request)
     end)     
end

function check_wifi()
 local ip = wifi.sta.getip()

 if(ip==nil) then
   print("Connecting...")
 else
  tmr.stop(0)
  print("Connected to AP!")
  print(ip)
  make_call("18889866685","155534566809","Your house in on fire!") 
 end
 
end

tmr.alarm(0,2000,1,check_wifi)