Holtek Decoder

[Bruce]

Hey George,

You're most welcome. It's pretty old, but it's simple & it works.

You can improve the synch bit check part by replacing it with this;

IF PBIT[0] <= PBIT[1] THEN Begin
IF PBIT[1] >= PBIT[2] THEN Begin
IF PBIT[2] <= PBIT[3] THEN Begin

And you can remove this part; IF Loops > 2 THEN Begin

I stripped a lot of code out before posting it, but missed that line. It's bits &
peices of a much larger program that was a first go at decoding the Linx
hand-held.

[richb20b]

Having spent a couple of hours decoding the output from a Holtek HT600 encoder (in a Micromark wireless burglar alarm system), using the voltage divider / sound card / audacity method, I decided to post the specs to save anybody else the trouble...

01 01 0 - 5 bit header
01 01 01 01 01 - A0 A1 A2 A3 A4
01 01 01 01 01 - A5 A6 A7 A8 A9 (note A5 doesn't exist and is always 01)
01 01 01 01 01 - NA AD11 AD12 AD13 AD14
01 01 01 - AD15 NA NA

As noted, there is no A5 pin on the chip - this results in 01 always being present in this field. I'm not sure what the final four bits do, they always seem to be 01.

Hope this helps. I'm hoping Bruce's code will decode this - otherwise I've got the info to write my own :-)

[richb20b]

Having spent a couple of hours decoding the output from a Holtek HT600 encoder (in a Micromark wireless burglar alarm system), using the voltage divider / sound card / audacity method, I decided to post the specs to save anybody else the trouble...

The pulse train looks like this:

01 01 0 - 5 bit header
01 01 01 01 01 - A0 A1 A2 A3 A4
01 01 01 01 01 - A5 A6 A7 A8 A9 (note A5 doesn't exist and is always 01)
01 01 01 01 01 - NA AD11 AD12 AD13 AD14
01 01 01 - AD15 NA NA

0 (pin pulled low) is encoded as 00
1 (pin pulled high) is encoded as 11
- (pin left floating) is encoded as 01

A[0-9] is the address pin (these are connected to DIP switches on my alarm), AD[11-15] are the data pins - these are connected to other switches corresponding to the data that should be sent. As noted, there is no A5 pin on the chip - this results in 01 always being present in this field. I'm not sure what the final four bits do, they always seem to be 0, 1, 0, 1.

Between A9 and AD11 there appears to be two sync bits. These appear to be always 01.

Hope this helps. I'm hoping Bruce's code will decode this - otherwise I've got the info to write my own :-)