GSM/GPRS Modem Board

This week we tested our new Telit GL868-Dual GSM/GPRS board. The GL868-Dual is a dual band 900/1800 MHz GSM/GPRS device.

This board is suitable for providing cloud connectivity to a remote instance of a WiSense wireless mesh network. The board can work directly off a Li-Ion battery which could in turn be charged by a solar panel or even mains AC if available.

This board can be easily interfaced to a Raspberry PI using an USB to serial (RS-232) adapter. The 5V output of the Raspberry PI should be used to power the board’s comm interface (see supply (2) below).

The GL868-Dual board can also be interfaced to an external micro-controller such as the MSP430 on a WSN1120CL coordinator node. The external micro’s supply voltage can be different from the power supply provided to this board. This is possible since this board utilizes voltage translator ICs for all exposed GL868-Dual signals. The external micro’s supply voltage should be used to power the board’s comm interface (see supply (2) below).

The GL868-Dual peak current draw is around 2 Amps.

Interfaces:

• Power supply (1): 3.8V  to 4.2V  (Allows the board to work directly off a single cell Li-Ion battery) through 4 pin screw less terminal block.
• Comm interface voltage supply (2) allows board to be interfaced with external micro-controller / R-PI etc through multiple voltage translator ICs. This is independent of the power supply (1) mentioned earlier.
• Mini-SIM card holder
• Comm interface:
  • RS-232 (TX/RX) through a  DB-9  connector
  • UART (TX/RX) on 2.54 mm pitch headers.
• Other exposed GL868-Dual signals (through voltage translator  ICs) on 2.54 mm pitch headers.
  • RESET_M
  • ALARM_M
  • BUZZER_M
  • RFTXMON_M
• External signal which controls a load switch gating power supply (1) to the GL868-Dual modem.
• Antenna  connection through u.fl connector.

PCB specs:

• Layers: 4
• Dimensions:  69 mm x 82 mm
• Finish: ENIG
• Mounting holes: 4
• All components mounted on top side.

Here is a  pic of the board.

For more information on WiSense  products, please visit wisense.in.