Send SMS with arduino or receive phone calls with arduino … If you are interesting in send/receive SMS, phone calls, emails … and more (like GSM Location) in this post my notes about SIM900 Arduino shield.

Index

• Main features
• What we need to use (buy)
• SIM900 Shield hardware layout (pins, jumpers…)
• How to send commands (serial terminal apps)
• Connecting (without using Arduino)  computer⬌sim900
• Try with AT Commands (Cut & Paste) (AT commands examples)
  • examples: simple tests / handle SMS / handle phone calls / GSM localisation / send emails

SIM900 Arduino shield

SIM900 is a wireless module for M2M applications now in EOL (replaced by SIM800x). This module is quad band (850/900/1800/1900MHz) with a built in core AMR926EJ-S .
The processor is an general-purpose microprocessor of ARM9 family: 156Mhz/1MB RAM  which supports 32-bit/16-bit instruction set (more details about AMR926EJ-S here). SIM900 is a module that is mounted on PCB with different layout depending on vendor.

In this post my notes how to test the SIM900 shield quickly without arduino and code (notes are related to this SIM900 Shield ),

… details here http://simcom.ee/modules/gsm-gprs/sim900/
–
… about the Shield SIM900
–

Main features

 (*) TTS Note  TTS through AT command but…available only for some versions! requires special FW and HW.
 The Shield in this post doesn’t support TTS.
–
 (**) GPIO Note GPIO can expand your arduino. GPIO are addressable through AT commands.
 The shield in this post supports 12 GPIOs and 2 PWMs

What we need to use

Grand Total: ~50 €

SIM (2G Network)

About SIM you need a 2G SIM with the proper price plan.
The SIM has to be for 2G Network with  “2FF 25mm x 15mm x 0.76mm – Mini”  factor.

In my tests I sent plenty of SMS and spending $$$ … IoT and M2M SIM are not easy to evaluate and choose.
So depending on the usage of this Shield  a regular 2G SIM with a low price for SMS/Data and a pay-as-you-go plan should be the best choice to start quickly.

Read  this (GiffGaff SIM) .

Warning! keep in mind to unlock the SIM turning off the PIN before inserting in the shield.

SIM900 Shield hardware layout

SIM900 Leds status codes

LED	Status	Meaning
Power led	OFF	SIM900 shield is not powered (no power)
	RED	SIM900 shield is powered (power is ok)
Status led	OFF	Power off
	RED	Power on (SIM900 is on)
Network led	OFF	SIM900 is not working
	64ms RED / 800ms   OFF	SIM900 does not find the network
	64ms RED / 3000ms OFF	SIM900 finds the network
	64ms RED / 300ms   OFF	GPRS communication

SIM900 images

How to send commands

Commands are sent to the Shield through the Serial port on-board of the Shield (see layout “Hardware Serial” here).  So we can communicate with the SIM900 sending AT commands through the USB port (using an converter).

A command to the Shield can be sent by a PC (as said) or by Arduino :

• Using a PC through an USB to TTL converter as shown here
• Using Arduino through SoftwareSerial Library (not described in this post)

For quick tests (using PC instead of arduino) you need to use a serial terminal application such as Arduino IDE (serial monitor), screen, minicon, cu, CoolTerm or putty.

screen (shell)

In order to send AT commands the easiest way is to use shell commands like screen (linux and OSX) :
1 Search Serial

ls -1 /dev/tty.* 
/dev/tty.Bluetooth-Incoming-Port 
/dev/tty.SLAB_USBtoUART 

2 Connect

screen /dev/tty.SLAB_USBtoUART 19200 -L
AT
OK

Exit screen and terminate the serial session with key :
 CTRL  + A + \

minicon (shell)

minicom -b 19200 -D /dev/tty.SLAB_USBtoUART

Configure “Hardware flow control: NO” and “Software Flow:control:YES” pressing keys :

•  CTRL  + A + Z 
•  o 
• Select menu option “Serial Port Setup“
•  F 
•  G 

cu (shell)

sudo cu -l /dev/tty.SLAB_USBtoUART -s 19200
Connected.

To exit from cu by typing keys: ~ .

Screenshots: screen, minicon and cu

Connecting (without using Arduino)

As said communication can be done using Arduino or using USB of your PC (with USB to TTL converter). In this last case you need to wire as described in below image.
Warning! Please pay attention to set PCB jumpers (serial selector) as “Hardware Serial“.

Try with AT Commands (Cut & Paste)

Using serial terminal application (here) you can send the following AT commands to the Shield.

Commands are described  in “Sim900 AT Commands (list of sim900 commands)” here. Below are examples related to network, clock, SIM status, Battery…

Below commands are related to SMS (receive, send, list and delete). Commands are described in “Sim900 AT Commands (list of sim900 commands)” here.

Phone calls and Calling Line Identification Presentation…Commands are described in “Sim900 AT Commands (list of sim900 commands)” here.

Example for GSM location …Commands are described in “SIM900 GSM location AT Commands (geolocalisation)” here

Send emails and get IP network…  Commands are presents in “Sim900 e-mail AT Commands (to send email)” here

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