Raspberry Pi zero GSM/GPRS extension hat
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datasheet Update documentation Nov 9, 2017


Welcome to NadHat.


NadHat is a GSM/GPRS modem extension hat for raspberry pi. It's pi zero hat format compatible (30x65mm). It uses the well known SIM800C module to offer a low cost M2M communication interface.

You'll find in this deposit schematics, datasheets and application notes, some pieces of software written in python and more in the future.

You can also follow nadhat google+ collection : https://plus.google.com/collection/o2lZRE

Have fun.

The garatronic team.


Don't want to read the manual, here a quickstart guide :

Serial port setup

default setup for serial port /dev/ttyAMA0 is 115200,8,N,1

Some usefull at command for SIM800C :

  • at : answer OK is serial setup is OK
  • atz : reset default configuration
  • ati : display product indentification information
  • at+cgmi : display product manufacturer
  • at+cgmm : display model identification
  • at+cpin? : check if pin number is required
  • at+cpin=xxxx : enter pin code
  • at+cbc : battery voltage (around 67% or 3940mV)
  • at&v : display current configuration
  • at+csq : report quality of signal (first nb between 0-31, 2nd nb between 0-7, bigger is better)
  • at+gsn : request TA serial Number Identification (IMEI)
  • at+cimi : request international subscriber identity
  • at+cops=? : report list of present operators
  • at+cspn? : get service provider name from sim
  • at+cadc? : read adc input (0-2.8V range, pin 7 of CN2)
  • at+cpowd=1 : normal poweroff

Send an SMS :

  • at+cmgf=1 : sms in text mode
  • at+csca="+33695000695" : service provider sms center number (french provider FREE for me)
  • at+cmgs="+3363054xxxx" : start SMS edition to "receiver number" prompt become '>'
  • input your SMS +
  • send hexadecimal chars '0x1A,0x0D' ( in fact) : to send your SMS

Receive an SMS :

  • answer the SMS you've received on your phone by NadHat.
  • should receive 'CMTI:"SM",x' meaning you have receive a SMS in slot x
  • at+cmgr=x : read sms in slot 1
  • at+cmgd=x : delete sms to free slot x for next SMS