DSC alarm keypad - trying to interface with microcontroller - Page 1
Forum section: electronics / projects

author: mayor
author_rank: Regular Contributor
timestamp: December 30, 2016, 01:15:40 am
content: Hello,I've googled a lot to find pertinent info on how to interface a DSC alarm system keypad to any microcontroller, but haven't been able to get the keypad to work (it basically lights up its error LED after a while).1. I'm testing with an arduino uno for the moment, and am shifting the signal level from it to 12v for the keypad (level looks good on the oscilloscope).2. Providing a 1kHz clock on "yellow" (per, among othershttp://electronics.stackexchange.com/questions/11017/dsc-keybus-protocol)3. Tried to initiate communications with PC1555 and LCD5501 keypads4. I don't have a DSC control panel to use to listen to communications - am I out of luck? (the keypads don't "talk" at all, and use a proprietary uC).If you've managed to interface either of these panels, I'd love to hear about it!

author: packetbob
author_rank: Contributor
timestamp: December 30, 2016, 01:55:03 am
content: Many years ago I planned to do something similar and found the below information in a sci.electronics Usenet posting from 1994..Never got around to doing it, so not sure if this was correct or not...Surprised that I had actually saved it and was able to actually find it...>I am looking for specifications on the communication between alarm panels>and the lcd/led keypads, the system i am looking for the most is the>DSC2550 panel and LCD600 keypad. If you have *ANY* specs on any alarm>panels and there serial communications between panels and keypads please>send me email.The first reply to this thread is in error ... here is the correct version:The DSC serial keypad link (which is used by most of their low end panels1500 - 3000) specifications are as follows:Red = +12V IMax 126mA INominal 30mABlack = GNDYellow = CLOCKGreen = TX/RXNote: The LCD keypad has a Micro which has preprogrammed key sequencesto make the interface more user friendly. The actual serial protocolis still the same as the regular led keypads.For the 16 zone DSC 3000 the following protocol is used:column 1 column 2 column 3row 1 1 2 3row 2 4 5 6row 3 7 8 9row 4 * 0 #row 5 Fire Ambulance PoliceThe serial protocol is made up of a continuous stream of multiplexed data.Forthe RK3000 (which has 24 indicators) a data stream of 47 1mSec cellsfollowedby a 22mSec sonalert cell (69mSec total). The odd cells are used for thekeypad row/column closures and the even cells are used for the 24indicators.Note: The keypad outputs have open collectors to allow parallel operation.Suspect the 1500/1550 will have a smaller data frame as the RK3000 isnot compatible with the 1500/1550. The 2500/2550 may also have asmallerframe. The LCD keypad will likely adjust to the appropriate framesizeand know the applicable key sequences for each panel.The RK3000 69mSec serial clock frame is as follows: (Clock)|<------------------69mSec------------------>|| |<--22mSec-->|--------+ +--+ --+ +-- --+ +------------+48 |01|02|03 ... 16|17|18 ... 46|47| 48 |+--+ +-- +--+ +--+ +The RK3000 69mSec serial data frame is as follows: (TX/RX)|<------------------69mSec------------------>|| |<--22mSec-->|--------+--+--+-- --+--+-- --+--+------------+

author: mayor
author_rank: Regular Contributor
timestamp: December 30, 2016, 02:19:20 am
content: Thanks for the reply. Amazing that you'd find such a "relic" :-)Looks like the clock is the same in today's models at 1 kHz, but info gathered here and there seems to indicate that the frames may have evolved.Also, I can't sniff any data from the keypads I have until. Key presses don't send data yet. I suspect I have to convince them there is a control panel hooked up, and that's what I am really looking for. What do these panels need (besides the right clock) not to error out and lock up?