ESP8266 - nodemcu - http.get() tut nicht wie erwartet

[Falk W. (dl3daz)]

In folgendem Programm landet "user_http_get_cb" immer im Teil mit 
"print("HTTP request failed.")"

Die Daten werden trotzdem hochgeladen: 
https://thingspeak.com/channels/109206

Was mache ich falsch?

(NodeMCU 1.5.1 build unspecified powered by Lua 5.1.4 on SDK 
1.5.1(e67da894))

function user_wifi_init( ssid, password )
  wifi.setmode(wifi.STATION)
  wifi.sta.config(ssid,password)
  wifi.sta.autoconnect(0)
  wifi.sta.eventMonReg(wifi.STA_GOTIP, user_cb_wifi_got_ip, "state")
  wifi.sta.eventMonStart()
  wifi.sta.connect()
end

function user_cb_wifi_got_ip( prev_state )
  ip = wifi.sta.getip()
  if ( ip )
  then
    print ("Got Ip: " .. ip )
    status, temp, humi, temp_dec, humi_dec = dht.read(7)
    vdd = adc.readvdd33(0)
    print ("DTH Temp: " .. temp .. " Humidity: " .. humi .. " VDD: " .. vdd)
    user_http_get(temp, humi, vdd)
  else
    print ("No IP!!!")
  end
end

-- Sende Daten an thingspeak

function user_http_get(temp, humi, vdd)
  api_key="XXXXXXXXXXXXXXXX"
  host="http://api.thingspeak.com"

  url=host .. "/update?api_key=XXXXXXXXXXXXXXXXX&field1=" .. temp .. "&field2=" .. humi .. "&field3=" .. vdd 
  hdr = "Content-Type: text/plain\r\n"
  print ("Send: " .. url)
  http.get( url, hdr, user_http_get_cb( code, data ))
  print ("Done!")
end

-- Callback for http_get()

function user_http_get_cb ( code, data )
  print ("user_http_get_cb!")
  if (code == nil) then
    print("HTTP request failed.")
  else
    print("user_http_get_cb Code:" .. code .. " Data: " .. data)
    wifi.sta.disconnect()
    node.dsleep(10 * 1000000)
  end
  gpio.write(6,0)
end

print ("Start!!!")
gpio.mode(6,gpio.OUTPUT)
gpio.write(6,1)

user_wifi_init("XXXX.1","XXXXXXXXXXXXXX")

print ("Ende!!!")

Gruß,
Falk