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Firstly FirM stands for Franks Infra Red Messenger . It was a project that came about after several posting on the UKHA_D list regarding zoned ir both tx and rx using HomeVision. I already had a homebrew zoned ir tx /rx system so I thought I would give it a go. After building and testing tx and rx prototypes the FirM Controller is the result ,an 8 zone tx and rx unit.
I will describe the receive side of FirM first . The Zone Rx units are connected to a cat5 cable which supplies +12v power and carries the rx signal , rx active signal and the zone tx ir signal . When a Zone Rx Unit receives an ir signal the following happens , the received demodulated signal gets sent back to the FirM Controller which passes the received signal through to a 38khz repeater and the signal gets transmitted out to a stick on emitter located on HomeVision. Also the Zone Rx Unit sets its Zone Active signal High to indicate to the FirM Controller that its receiving an ir signal..This signal is a mono timer
The Pic micro located in the FirM Controller detects the received data and then scans the Active multiplexer and detects which zone the signal is coming from. It then turns on the appropriate Zone Rx led and also the Busy Output which goes to all Zone Rx Units illuminating the red led, a bcd value is outputted on 3 I/o pins connected to HomeVision indicating the Active Rx Zone ,if HomeVision recognises the signal it should then set its Ack output high to the pic which then turns off the Busy output and gets ready for the next receive signal. If HomeVision does not set Ack high there is a timer timeout (approx 5 seconds) and the pic gets ready for the next receive signal.
Only 1 receiver can be Active at any given time as All received signals are ored back at the FirM Controller ,thats the reason for the Busy output it informs all Zones that a received signal is being processed and to wait before sending an ir signal . Please note the FirM Zone Rx Units use 38Khz IR Receivers ..
See next page for Transmitter explaination which is much simpler
FirM User Document in Word Format
FirM User Document in PDF Format
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