A couple of pics of my HV I/O Expander Module...This device was initially designed for my FirM and Probe systems. It allows both FirM + Probe system to connect to Homevision via Homevisions Expansion Bus.. Freeing up valuable I/O in the process..

Decided to make it a general purpose I/o module and as an input module its the same as Port C of Homevision. As an output module its the same as Port A....

The green terminal block is for inputs (8 off) and the orange terminal block is used for outputs(8 off) . Im using the boards for FirM + Probe in a mixed I/o setup but I think its simpler to use either as an 8 input module or an 8 output module.

Initial testing went well with FirM + Probe connected. But when I connected an input and output module it all fell over... I could only get it all working if I used very short bus cables....After some help from the HV List I decided to reduce the i2c pullup resistors to 1k5 and this allowed me to use 1metre leads again....

I now have 6 units connected to the bus, FirM , Probe ,input module ,output module ,input module ,output module..............and all are working ok so far....Im using a retriggerable timer to poll the inputs (every ½ second) and reflect their status via leds connected to adjacent output modules...

The polling doesnt appear to burden Homevisin too much , but it would be possible to miss a quick changing input if Homevision was processing other events such as ir signals or x10 commands...

In my application I will be connecting to my alarm system via relays and can program the relay on time to a couple of seconds to be sure ....Although since im only using this setup to trigger some lights it wont bother me if the odd trigger is missed....
More Soon