SM5100B GSM/GPRS modem – useful AT commands

Latest version of this document can be found under source control here on github.

1) Reboot modem


+SIND: 1

+SIND: 10,”SM”,1,”FD”,1,”LD”,1,”MC”,1,”RC”,1,”ME”,1

+SIND: 11

+SIND: 3

+SIND: 4


2) save settings (whatever can be saved) to non-volatile memory


3) display error text instead of error code


4) enable local echo


5) date time (which will be incorrect)

check date time:


+CCLK: “14/03/15,00:12:18”


set date time:
total 17 chars formatted as – “yy/mm/dd, hh:mm:ss”


minicom trace

6) check misc status flags


+CIND: 0,19,1,0,1,0,0,0


The format is:

+CIND: <battery>, <signal level>, <service>, <sounder>, <message>, <call>,
<roam>, <smsfull>

<Descr> description
– battery Voltage of battery
– signal Strength of signal (0-31)
– service Availability of network (0-1) (value=1 means registered to network)
– sounder Stillness (0-1) (1=mute)
– message Whether receive short messages (0-1)
– call Existence of a call (0-1)
– roam Net status (0-1) (1=roam status)
– smsfull Short message memory storage has become full(1), or memory locations are available(0)

7) display sms in plain text



8) read sms at specified index (0 is invalid)

+CMGR: “REC READ”,0,”+14088494245″,”13/07/26,23:34:24+00″
Hello cellular prowl

+CMGR: “REC UNREAD”,0,”+14088494245″,”13/07/26,23:36:40+00″
Meow meow purrrr


9) delete sms at specified index (1 in this case)



+CMS ERROR: Invalid memory index

The format is:


<index>: index num of chosen memory <mem1>,which should be less than the maximum num item of <mem1>

<DelFlag> description
– 0 Delete an message according to index
– 1 Delete all readed messages
– 2 Delete all readed or sent messages
– 3 Delete all readed or sent or unsent messages
– 4 Delete all messages

10) list all sms

+CMGL: 2,0,”REC READ”,”+14088494245″,”13/07/26,23:36:40+00″
Meow meow purrrr


11) make a call


12) hang up a call (ringing or received)


13) answer a call


14) send sms


> hello kitty▒
+CMGS: 1


NOTE: That funny character above is ctrl+z; sending ctrl+z is equivalent to sending a single byte with the hex value: 0x1a

Sparkfun GSM/GPRS SM5100b shield on a Diavolino

I have decided to return the SM5100B evaluation board since I am instead using the SM5100B cellular shield. This is because I was not really going to use any of the interface pins of the SM5100B module broken out on the eval board. One useful thing about the shield (that I wasn’t expecting) is that it is able to reset the cellular module using the on board reset button similar to the eval board.


The Diavolino board here is running without any AVR 328 mega chip plugged into it, and has the 2.5mm x 5.5mm power barrel socket for the 5V 3A regulated power supply from EvilMadScience.

Diavolino hosting a GSM/GPRS shield

Meanwhile although I can receive TCP data on the SM5100B modem over GPRS I still haven’t been able to successfully confirm transmission of data.

Basic testing the SM5100B

SM5100B GSM GPRS modem setup

The parts for the first phase have arrived and basic functionality of the GSM modem was tested and found to be operational. Here is a log of the modem receiving a phone call:

+SIND: 1
+SIND: 10,"SM",1,"FD",1,"LD",1,"MC",1,"RC",1,"ME",1
+SIND: 11
+SIND: 3
+SIND: 4

Here is a list of what I’m using:

  1. From SparkFun
    1. SM5100B Evaluation Board
    2. GSM/GPRS Module – SM5100B
    3. Quad-band Cellular Antenna SMA
  2. From EvilMadScience
    1. 5V, 3A Regulated Power Supply
  3. From BG Micro
    1. 2.5mm Jack To 2.1mm Plug

I also tested receiving SMS text messages but it seems that, they aren’t pushed over the UART. Instead I had to poll to check if I had received any new SMS messages.

+CMGL: 1,0,"REC READ","1511","12/09/09,00:29:11+00"
Welcome to T-Mobile! Dial #BAL# to check your balances. Your T-Mobile number is 1***412****
+CMGL: 2,0,"REC READ","+1***721****","12/09/09,01:14:02+00"
Hello, world
+CMGL: 3,0,"REC READ","+1***721****","12/09/09,01:16:33+00"
Hello, world 2

I am currently using this with a T-Mobile pay-by-the-day plan which gives me unlimited voice, text, and 2G data for $2 per day.

Next I am going to spend some time thinking about how I want to proceed.