using keypads without alarm panel

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using keypads without alarm panel

Postby edge9421 » Mon May 11, 2020 8:43 am

I'm researching feasibility of using my XL-4500SM keypads with Home Assistant and found this product. Although this product is the opposite of what I want do do, I am hoping some of the protocol knowledge will be useful for my project. My motivation for this project is that my wife is far more comfortable with conventional keypads than fancy tablets. There is also something nice about physical buttons and LED's.

I took my FBII XL21 alarm panel out of service when I bought this house a couple years ago and replaced it with a Konnected device to interface the wired sensors and siren with my Home Assistant. I still have the XL21 laying on my workbench in case I need it to reverse-engineer the signals, but avoiding that would be nice. From what few clues I have found so far, it seems like there is a chance this is an RS485 serial bus? I have an RS485 to USB adapter available to experiment with but wanted to get more info before attempting to connect it to the keypads or the XL21. I found this page with protocol info, but it's not obvious to me that's purely the Alarm Decoder software protocol or if any of that is the raw bus protocol, and whether this is RS485 or something else.

Any help with the raw protocol is greatly appreciated. Thanks!
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Re: using keypads without alarm panel

Postby edge9421 » Wed May 27, 2020 6:47 am

Does anyone have any thoughts on this?
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Re: using keypads without alarm panel

Postby frogger77 » Thu May 28, 2020 2:02 pm

You probably won't get the raw protocol here, the keys the the kingdom, as they say.

The protocol page should be useful. You have the unknown of the AD microcontroller, which is decoding and encoding packets to be on the bus. But if you have the bus and the device, you can see what's going on each end. But I would imagine you would need to transmit packets that the device won't send.

You can see here: https://forum.arduino.cc/index.php?topic=255297.0 someone else was able to get it started at 4800 baud, but the hardware uart had issue and software uart did not. This tells me this guy don't know what he's doing or they are playing tricks somehow. (ie. funkify the stream with bits in places where hardware uart can't handle it). This would explain the need for a micro to interface bus to a RPi.

I hate it when they do that. 4800 baud is plenty slow and shouldn't be hard to figure out. Best one I ever encountered was 900+kbps serial stream that had 1st 3 bytes with even parity and rest of packet had odd (or other way around). Hardware UART could not deal with it, so had to upgrade my micro to something way faster and then bit-banged it.
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