This project is adds on from the first serial converter. In addition to the features of the first serial conversion module, this circuit also includes activity LED's. The ability to visualize activity is very useful when de-bugging projects. The LED's have been optimized to make it easy to see activity even at high baud rates.

As with the previous converter, this one is built around the famous MAX232 chip (any equivalent is fine). Check that the flavor of chip you get uses the same value caps (e.g. MAX232A uses different values). A 5v DC source is required; the ground signal should be common with the target board supply.

Basic serial handshaking is also converted (CTS, RTS). The other handshaking lines can be linked as required with jumpers. For testing a jumper between Rx and Tx will create a repeater node, just check using HyperTerminal etc.

Each LED is controlled by two 555 timers. The circuit is configures as two independent one-shot vibrators. One 555 is used to fix the 'on' pulse, whilst the other ensures that there is always a consistent break between 'on' states. This creates a clear display, however if you wish to adjust the timing resistor\capacitor values can be adjusted.

A note on connections: I use small jumper cables to link the converter to the microprocessor or power supply. These are made up with small connectors (available at any electronics supply shop) crimped, soldered and insulated with heat-shrink. This method is quicker and neater than screw terminals etc. An added benefit is that the lines can be linked back with a standard IDE jumper.

For a great PC terminal tool check out WSHDCOM (www.wSHDCom.com). This tool allows you to send and receive serial data in a number of formats including HEX and binary, very handy for debugging microprocessor projects. Best thing about this program, it's free!