User Interface Description

12.07.2009 13:35

Please look at the initial page - how to start with if you want to get thorough information.


User Interface

There is a picture showing a User Interface of GSM Playground for the important things placed from top and bottom PCB side. Most of the things are clear from the picture and the important rest is described below.


ON/OFF Button

This button is intended for switching ON and OFF of the GSM Module. There is needed to hold the button for at least 1 second to switch the module ON or OFF. It is usable for "hand" controlling of the module or during software development.


Power Indication LED

This yellow LED indicates that the GSM Module is connected to the power (3,9V).


GSM Status Indication LED

This blue LED is controlled directly from the GSM module and it indicates the status of its operation.

LED status GSM Module Status
Permanently OFF Device OFF
Fast blinking (- - - - - - -) Net search / Not registered / turning OFF
Slow blinking (-     -     -) Registered to network
Permanently ON A call is active


Speaker Connector

This connector (2 pin header 2,54mm) is located at the bottom side of the PCB and it is prepared for connection of 8Ω speaker. The audio amplifier is able to supply the speaker with power 800mW.  You can find how to use it in the document with Description of useful AT commands. We provide suitable Loudspeaker or Mini Loudspeaker  - both are equipped by appropriate connector.



The buzzer can be used instead of a loudspeaker if only needed to produce sounds and ringing tones. It is much smaller than the speaker and located directly on the PCB. So the buzzer is suitable for applications without voice calling. You can find how to use it in the document with Description of useful AT commands.



This is a sensitive miniature electret microphone intended for several applications based on voice calling. You can find how to use it in the document with Description of useful AT commands.


Connectors for an Arduino Board

This is a connection point to the Arduino Board. There are used stackable pin headers so you can place other Arduino shield on the GSM Playground if needed.

The GSM Playground uses following inputs and outputs

0 RX_CPU/TX_PC serial DATA to CPU or serial DATA from PC  
1 TX_CPU/RX_PC serial DATA from CPU or serial DATA to PC  

DTMF_ENABLE=HIGH -> DTMF Outputs (D0-D3) Enabled

DTMF_ENABLE=LOW -> DTMF Outputs switched to high

impedance and PINs 6-9 usable for other purpose


If VALID DTMF tone received -> DTMF_VALID=HIGH,

otherwise is LOW


Tie GSM_RESET to HIGH for at least 0.2 seconds to reset

the GSM modul


Tie GSM_ON/OFF to HIGH for at least 1 second to turn

ON or OFF the GSM modul

6 DTMF_DATA0  Receiving data output - DATA0 *
7 DTMF_DATA1  Receiving data output - DATA1 *
8 DTMF_DATA2  Receiving data output - DATA2 *
9 DTMF_DATA3  Receiving data output - DATA2 *

 note: (*) - the signals can be used also for other purpose


SMA Connector for GSM Antenna 

This connector is intended for connection of GSM Antenna with the following parameters:

Frequency range: It depends on the network operator. Our Quad band antenna can be used with all possible GSM frequencies.

Gain: < 3 dBi

Impedance: 50 Ohm

Input power: > 2 W peak power

VSWR recommended: <= 2

Connector: SMA Male


SIM Card Reader

This is the connector where is needed to put the SIM card. The right placement is shown on the PCB close to the SIM card reader. 


Switch for serial communication:

The GSM Playground offers an easy way how to deal with different requirements for the serial communication between PC, GSM Module and Arduino board. There are electronic switches (4066) placed on the PCB controlling the way of serial communication. Those switches are driven by the mechanical switch S1 (right section) with following states.

ON (top position)

The GSM Module is connected directly to PC through the Arduino board. There is possible to open some terminal software on a PC and communicate directly with the GSM Module using AT commands in this state. This mode is such as learning mode because it is suitable for training and trying of different AT commands. You can look at the document with Description of useful AT commands. The GSM Playgroud can be also used as a GSM/GPRS gate if it is needed of course.

Note: The Arduino board is held in the RESET state while this kind of communication is chosen so there is not needed to remove the ATmega from the board!

OFF (Bottom possition)

The Arduino board is connected to PC so there is possible to program the board using the Arduino software. Furthermore the GSM Module is connected to the microcontroller (CPU) on the Arduino board also so that the Arduino board is able to communicate with the GSM Module. 

The Arduino board can simply communicate with both devices (PC and GSM Module) because the GSM Module can only answer for particular AT command so it doesn’t disturb the communication between Arduino board and PC during programming.

Note: There is needed to switch off the repeating of commands by the GSM Module using an AT command ATE0 before using of this mode. This will make the GSM Module quiet during the programming from Arduino software. Sometimes it might happen that the module disturbs the communication between Arduino software and Arduino board but it doesn’t have any influence to programming because it is just at the end of the programming. There is possible to switch off the GSM module using ON/OFF button and then the GSM Module is completely quiet :-).


Switch for battery operation and Battery connector

The switch can allow supplying of the GSM Module and Arduino board from a battery connected to Battery connector and charging of the battery using an internal charging circuit located in the GSM Module. There is needed to have a suitable battery LiPol 3,7V with capacity 500mAh to 1000mAh with a JST connector. An appropriate battery is 1000mAh LiPol battery or 860mAh LiPol battery.

Before the battery can be connected to the Battery connector there is needed to switch ON the Switch S1 (left section) for battery operation. It will disable 3,9V power supply for the module and enable the current source 200mA for supplying of the charging circuit in the GSM Module. The current source is supplied from 5V so there is recommended to use the battery together with USB as a power source. In case you connect the adaptor it is also possible but there will be significant power loss (it will be hot) on the Arduino 5V regulator. This regulator has a built in over temperature protection so it is allowed but be aware that the 5V regulator can be quite hot during charging of the battery.


Temperature Sensor

The sensor is placed from the bottom side of the PCB close to the antenna connector. The voltage coming from the temperature sensor is measured by the GSM Module and it can be easily evaluated by AT command. You can find how to use it in the document with Description of useful AT commands.


User LED and User Button

These parts can be used as a simple output and input in your application or just for software development purpose. You can find how to use them in the document with Description of useful AT commands.


User Connector with GPIO

This connector can be used as a way how to control or sense another circuits because it contains 4 general purpose inputs / outputs. You can find how to use them in the document with Description of useful AT commands.


DTMF Indication LEDs

These indicators are connected directly to DTMF receiver and show the value of received DTMF signal. Check the PCB circuit diagram and DTMF circuit based on Holtek HT9170 ifor more details.


© 2015 Všechna práva vyhrazena.