GSM/GPRS Modem

See also: sim800

A GSM/GPRS modem is used to simulate the Iridium modem. It is cheaper to use GPRS data than Iridium credits when testing.

Following GPRS modem is used (SIM900), but any equivalent is ok: http://www.geeetech.com/wiki/index.php/Arduino_GPRS_Shield

Protocol: AT Commands via UART
The factory default setting for the GPRS Shield UART is 19200 bps 8-N-1
CR only after an AT command!
Uses 2.8V logic. Voltage divider hack should suffice for experiments (1k/5.6k)
AT TCP connection: https://vsblogs.wordpress.com/2013/11/28/tcp-connection-over-gprs-using-sim900-and-at-commands/
AT+CIPSTART=“TCP”,“www.bitmorse.com”,“1990”

Example: POST to basestation with AT commands

AT+CIPSHUT

AT+CIPSTATUS
AT+CIPMUX=0

AT+CSTT="gprs.swisscom.ch","",""
//AT+SAPBR=3,1,"APN","gprs.swisscom.ch"
//AT+CDNSCFG = "8.8.8.8","8.8.4.4" 



AT+CIICR
AT+CIFSR   

AT+CIPSTART="TCP","basestation.octanis.org","80"
AT+CIPSEND=166


POST /heartbeats HTTP/1.1
Host: basestation.octanis.org
User-Agent: ALETSCH
Content-Length: 22
Content-Type: application/x-www-form-urlencoded

temp_in=34&temp_out=40