More documentation is available at Circuit Cellar Renesas Design Contest 2005 and in the January 2007 issue of Circuit Cellar (#198)

Introduction

QuickComs is a useful M16C/62P micro-controller based system that can be connected to an RS232 device to determine the correct wiring, data rate and encoding scheme. It can be used to monitor a serial link as well as acting as an automatic null modem cable. QuickComs can be inserted inline to a serial link or connected to a single device.

This project should be useful to anyone who often works with older scientific or industrial equipment (especially where instruction manuals are often misplaced or lost with time), or to anyone who has the need to quickly troubleshoot a serial connection in a micro-controller system. It has already proved useful for quickly revealing situations when the system or UART clock was running at an unexpected speed. This is fantastic in a teaching lab when a student's breadboard circuit doesn't work first time. This project also gives those without a scope the power to determine the communication parameters of equipment without the need for in-depth knowledge, a turnkey solution for the front-end developer.

Photo 1 Top view of the Renesas development board and sampling and scaling electronics. CLICK TO ZOOM		Photo 2 The component side of the prototype board with the Renesas board folded out of view. CLICK TO ZOOM

As can be seen from Photo 1, the current design is only a prototype and as such is not as portable as a commercial product might be (nor is it as pleasing to look at). I imagine it to be quite straightforward to take this design and optimise it for commercial production in a package not much larger than a standard deck of cards (similar to the Atlas range of products from Peak Electronics Design).

Motivation

The inspiration for this project came together from various sources and situations including: my own debugging of old lab equipment, the need to quickly diagnose a broken serial link in a micro-controller system during the design phase, the need to quickly debug student designs in a teaching lab environment, and to assist those without a scope to determine the communication parameters of old equipment where the manual has been lost.

A few years ago a friend of mine, who was working developing front-end systems for databases, had been given a project that needed to communicate with some electronic scales. They were given some scales and cables, but that was it; no baud-rates, parity bits or stop bit information. I was asked if there was any easy way to determine the communication settings of the device, I asked if they had a scope, "a what?" was the reply. Eventually they figured out that the device used 1200-7e1 by trial and error; I thought there should be a better way.

For me figuring out the exact baud-rate, encoding and wiring scheme for the serial connection on that really old piece of equipment at the back of the lab has always been part of the fun and challenge of being an Electronics Technician. But then again, not everyone can just run off and grab a scope or logic analyser and come up with an answer. Sometimes having to repeat the process ten times in a single lab session as students learn the ins and outs of working with micro-controllers can be a bit tedious and take some of the fun out it. These are some of the reasons why I designed the QuickComs prototype.

With RS232 quickly being replaced by USB, the nightmare of incorrectly wired appliances and forgotten baud-rates will hopefully be a thing of the past. Unfortunately RS232 will still be with us for a long time to come and, as it becomes used less frequently, the exact parity and baud-rates for devices can easily be forgotten.