Specifications

You can get the schematic I used for all my detection here! Just look up the MT8843. I originally used a 7805 and a 9v battery for power. (Available from your nearest radio shack). But, it doesn’t last very long. So, just connect the positive side AC/DC converter (from 6-12v DC output) to the left pin, and the negative to the middle. Then, the right pin will have a nice 5v ttl output for you!

Directions

Well, you can probably tell this from the C-program’s header, but here goes anyway… You connect the parallel port pins of your computer to the device as follows:

• Pin 11 -> TRIGout
• Pin 10 -> INT
• Pin 12 -> DCLK
• Pin 13 -> DR
• Pin 15 -> DATA
• Pin 2 -> POWDN
• Pin 25 -> System Ground (The middle pin on the 7805)

What the program does is keep POWDN asserted until it gets an INT. It should probably check to make sure a ring event has occured (TRIGout), but it doesn’t. Then, it negates POWDN, allowing the chip to run pulling full power. The Mitel 8843 is a power hog. I would not run it continuously in full power mode. (It got my 9v battery really hot!)

Anyway, that’s about it. The code I used is here: callerid.tgz. It runs under DOS and Linux. For linux, compile it with UNIX defined. It is very far from finished, but gives you enough to get started.