Machine To Machine "M2M" Communication - A Data-Logger With GPRS Connection

by Martin THOMAS

In this project which is currently under development a data-logger samples data from various sources and transfers the information thru a wireless link to an internet-server. The device can be powered by battery and is optimised for minimal current draw. The main functions of this device:

• Sample data from analog to digital converters which can be connected by RS485, SPI and I2C/TWI
• Store the data on a memory card
• Transfer the data to a internet-server by FTP or file-upload (RFC 1867) over GPRS
• Send alarm messages on configurable events by Short Message Service (SMS) or e-mail
• Time sychronisation from internet time-servers (RFC 868)
• Minimum power for Battery supply

The hardware is based on an ARM7-architecture controller. Some of the used components are:

• ARM7TDMI-S Controller Philips LPC2138 (maybe LPC214x or Atmel AT91SAM7xx with USB on future devices)
• GSM/GRPS Module from the DAI Telecom Telit GM862 series
• SD/MMC memory-card
• RS485 connection for external data converters and signal conditioners
• RS232 connection for firmware-updates (ARM and Modem), log- and debug-outputs
• Power Supplies
• Overvoltage and ESD protections
• Components for power-saving

The Software is written an C, care has been taken to keep the code portable (early developments have been done on an ATmega128 based system). The tools from my WinARM collection are used (arm-elf-gcc et al). "Device-Drivers" in this software:

• Interrupt-Driven UART with RTC/CTS Hardware flow-control for the GSM-Module
• UART-Driver with Transmit/Receive switch for RS485-communication
• SD-Card filesystem library (modified efsl)
• GSM routines (SIM-PIN/Network-Connect)
• GPRS routines (based on the Telit Easy-GRPS)
• Routines to handle the RFC1867 protocoll
• Routines to fetch the current time from the internet (RFC 868)
• Routines to handle the ICP-DAS DCON-protocoll over RS485
• RTC code for 32kHz XTAL
• Battery monitor/ADC
• Software-UART (3rd UART) for debug-output, monitoring and configuration

Currently there is no software an no schematic available for this project. But at least some pictures of the prototypes:

The first prototype is based on a Keil MCB2130 evaluation board. The RS485-modules and the GSM/GPRS module are connected externaly.

On the second prototype the GPRS/GSM-Modul is "On-board". All components have been selected for minimal power-demand

To my ARM-Projects page

To my Atmel AVR-Projects page

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