May 2006, Issue 190

ARM-Based Modern Answering Machine
Philips ARM Design Contest 2005 First Prize

TCP/IP STACK

This project required a TCP/IP stack. I didn’t have a lot of time on my hands, so I accepted the first attractive offer. I selected Adam Dunkels’s uIP embedded TCP/IP stack (www.sics.se/~adam/uip/). It wasn’t the best choice, but it functioned well. The stack is targeted for processors that are generally much smaller than the LPC2138. It carries some short cuts that wouldn’t be necessary for a 32-bit RISC processor such as the LPC2138.

Porting the stack was a straightforward task, except for the process of developing the Ethernet driver for the ENC28J60. Nevertheless, I quickly performed ARP resolution and a ping, and then established a TCP/IP connection in both Receive and Transmit modes.

The uIP stack came with example applications, but I had to modify them for the TAM-TAM. The SMTP mailer was the easiest to integrate. The TAM-TAM can be configured to automatically send an e-mail to a mailbox or to a cellular provider’s SMS gateway. The body of a message contains the following sort of information:

Received at 14:14 on 22/10

From: 860-875-2199

Name: Circuit Cellar Inc.                   

The name and phone numbers are extracted from the caller ID frame. The time comes from the clock, which is automatically set with any valid caller ID frame that carries the date and time information. The information is available even when the caller ID is missed.