thingspeak.agent.nut

local thingspeakUrl = "http://api.thingspeak.com/update";
local headers = {"Content-Type": "application/x-www-form-urlencoded",
                  "X-THINGSPEAKAPIKEY":"KEY"};
local field = "field1";
function httpPostToThingspeak (data) {
  local request = http.post(thingspeakUrl, headers, data);
  local response = request.sendsync();
  return response;
}


device.on("updateTemp", function(temp) {
   local response =  httpPostToThingspeak(field +"="+temp);
   server.log(response.body);
});

TMP36.device.nut

hardware.pin9.configure(ANALOG_IN);
 
function getTemp() {
    local supplyVoltage = hardware.voltage();
    local voltage = supplyVoltage * hardware.pin9.read() / 65535.0;
    
    local c = (voltage - 0.5) * 100 ;
    local c_str = format("%.01f", c);
    server.log("Current temp is "+c_str+" °C");

    agent.send("updateTemp", c_str);
    imp.wakeup(600, getTemp);
}
 
imp.configure("TMP36 Thermometer Thingspeak Logger", [], []);
getTemp();