This proved to be an interesting project, as i had to cater for several types of device, with varying output voltages and input voltages. One type of device i had to 'talk' to using RS 232 driven optical transmitters.
The main test unit drives led's at a rate of about 3Hz, but when they are 'ON', they actually modulate at 8kHz. This was done by implementing two 555 timers, although hindsight tells me to use a 556 to reduce dicrete component levels.
The device which is being tested, picks up these signals, de modulates them and drives a status led, which tells the operator that the device is working correctly.
The communications are handle by a LT1080CN chip, which converts RS 232 signals, generated by a test harness program, to TTl levels. These TTl signals drive communication led's which enable the software to test if the device will receive and transmit satisfactorily.
