Old Mobile Phone GSM Sim900 - Wiring

First thing first. What should we have. Old mobile phone should have GSM component, Keypad and LCD : D Yaa.. These things should be enough.

What you should have:

Main item
+ Arduino Uno (You should already have it : D )
+ Geeetech SIM900 Shield
+ LCD 20x4
+ 4x4 Matrix Keypad Membrane
+ Potentiometer

Optional item:
+ Donut board / Breadboard
+ Jumper wire
+ Soldering Kit

First you need SIM900. Any SIM900 shield should compatible with this tutorial. For this tutorial purpose, we will use Geetech SIM900 Shield available in our online store.

I repeat it again, any SIM900 shield should compatible with this tutorial.

1) You should have SIM900 Shield.

2) Make sure you have a Sim card with enough credit to send message and make a call. Install the sim card into sim900  shield.

3) Make sure the power selector is switch to Xduino label. This will make the shield to receive power from arduino uno Vin.

4) Make sure the serial pin selector is short with jumper to D7(RX) and D8(TX). We will not use hardware serial pin (D0 and D1) on arduino uno to communicate with SIM900. We will use D7 and D8 as software serial to communicate with arduino uno.

5) Make sure these two pad is solder bridge together. Initially it is not solder. This to tied up the power pin of sim900 to pin D9 on arduino. Later, we will write a program to power up the sim900 automatically using pin D9 arduino uno.

6) Then stack the geeetech sim900 shield on top of arduino uno.

7) Now we will create a pin diagram for arduino uno.

+ Geeetech SIM900 will use VIN, GND 5V, RESET, D7, D8, and D9.
+ LCD will use 5V, GND, A0, A1, A2, A3, A4, A5 and D10 (in this tutorial, i will leave D10 unused because we are using LCD without backlight. If you have, you may use it.)
+ Keypad will use D2, D3, D4, D5, D6, D11, D12 and D13.
8) Then we will go to keypad wiring. Hope picture below is enough for you to understand  : D

9) Then we will go to LCD wiring and one more time hopefully picture below is enough for you to understand.

10) Done. Then you may wired all things up. I prefer to wired all things using donut board, jumper wire and permanently soldered it. You may use breadboard and jumper or any way you prefer : D

11) Feel free to comment if you see any major fault or anything you did not understand or anything that you want me to edit or add up something. Just comment it below. See you soon on next tutorial. Done wiring. Next tutorial will be on software part : D The exciting part : D


  1. please post th code for the arduino.

    1. This page is for wiring sir , please visit the other page under tutorial :-)