THE ALPHABET PROJECT - professional Arduino, BeagleBone & Raspberry PI shields

Order product(s) of the week. Order u-GSM modems.
Read our last post: Modems and RaspberryPI 5. RaspberryPI OS [Debian 12 bookworm] notes..

Smart doorbell with Arduino and A-GSM shield by Pop Georghe



Sometimes I get frustrated that the guy from the delivery company or postman comes to my door and is too lazy to make a call telling me that I receive a package. Many times Im the lazy one when some friends come to my house and I need to go outside in the rain to open the door for them. Considering all this I develop a project to kill laziness :-). Just kidding.

I receive for testing purpose an Arduino GSM shield, called A-GSM made by R&D Software Solutions, a Romanian company from Bucharest. How better to test this shield if not to make a project with it.


About the project

Basically I build a smart doorbell. When you press the doorbell button it rings like a normal doorbell. The same happens the second and third time. But if no answer happens till now, at the fourth time the button is pressed, the doorbell will call you on your mobile phone number allowing you to speak with the person that is at your door. Also with the help of DTMF codes its allowing you to open the door from anywhere you might be in that moment.

So lets see if I managed at least to wound laziness.


Needed parts

  • Arduino UNO
  • A-GSM shield (a-gsm shield distributors or order online)
  • Doorbell shield
    • 1 button
    • 1  speaker for doorbell
    • 1- relay for door unlocking
    • 1 PC microphone for A-GSM sheield
    • 1 0.5W speaker for A-GSM shield
  • Power source


About A-GSM

At first I was a bit skeptical about the A-GSM shield, and maybe it was because its my first time that I was playing with a GSM shield. Looking at the documentation provided at I was able to get started very easily. Mainly if you are able to use the serial communication port from your Arduino you wont have any problems using the A-GSM shield. The code on manufacturer site touches all functions of the shield, yet a library for this shield would be very useful. The shield is based on GSM chip QUECTEL M85, if you need a function and is not provided by the sample codes you can check the  GSM_M85_AT_Commands_Manual_V1.0

Shield specs



  • Worldwide compatibility # quad band module
  • GSM / GPRS / SMS / DTMF supported
  • Two SIM sockets
  • Integrated GSM antennaand uFL connector for external antenna
  • Integrated uSD(TF) socket
  • Micro-USB interface- SERIAL to USB bridge adapter with micro-USB type B socket (you can use the a-gsm board as wireless modem with your PC, connecting it directly thought USB to your PC Windows and Linux compatible)
  • 3-5V serial interface
  • 5-38V wide voltageswitching power supply
  • Audio jacks (out-700 mW RMS, in- capacitor MIC)
  • DIGITAL AUDIO interface and SERIAL2 (3V TXD and RXD) interfaces available thought additional back PCB side pads.
  • MicroSD card socket standard (support uTF cards up to 32 Gb)
  • SERIAL TTL interface, down to 3V compliant (TX and RX) available in Arduino pin-out
  • Embedded switches: control for modem ON/OFF & modem RESET and Arduino Reset
  • Extended Arduino and RaspberryPI support, with code examples:  GSM, TCP/UDP, HTTP over GPRS, DTMF, SMS and other features and utilities like micro-TF CARD FILE SYSTEM STORAGE, DUAL SIM, others.
  • RaspberryPI PPP and TCPIP routing support (RaspbianOS) trough easy installation and usage scripts.
  • Complex code examples
  • Ideal for small-medium series gadget / project integration



In the picture bellow you can observe all the needed connections.



For the A-GSM speaker and MIC the connections should be done as in bellow picture:




Code is too big to put it all here and that is why I prefered to use GitHub


Possible improvements

  • Add LCD for telling the visitor what is happening
  • Re-positioning of the MIC for better sound quality
  • Build a box for the complete project





Originaly publised on 01/12/2014 by Pop Gheoghe at




About Pop Gheorghe

Passionate about everything related to programming. It is not especially focused to a particular language, but performs C and Python programming, for the moment. Graduate in 2005 the Faculty of Mechatronics at Universitatea Politehnica Timisoara.

He got the first computer at the age of 10 (it was a CHIP03 - still having it today). Currently is "playing" with Arduino and Raspberry Pi.



Order online a-gsmII shield -




document version 1.011 / 2015-05-28 © R&D Software Solutions srl