The Mysteries of the ELK M1G Databus

[Lagerhead]

Just FWIW -- "Application Note 1057 Ten Ways to Bulletproof RS-485 Interfaces"

 

[Spanky]

The first thing to understand about the ELK data bus is it is a RS-485 data bus with all modules wired in series and a termination resistor at each end of the data bus. If you power down the M1 and measure the resistance across the bus, it should read about 65 ohms +- 10 ohms. The normal problem is when an unterminated spur is wired off the bus and line echos start causing data bus errors. Short runs of a few feet are OK like in the control box.

Data bus errors that are displayed on the keypad are the number of times the M1 retries a message to a module. It is common to see a few errors. Maybe one every few minutes. If you can look at the keypad error display and see them counting up every few seconds, then you have a data bus problem. Normally a wiring problem. Make sure eveything is wired in series and a termination resistor is enabled at the extreme ends of the data bus.

Google RS-485 data bus for some good reading.

 

[pipeman]

I've completed wiring in my detached garage and have a keypad,(1) input and (1) output module, garage door programming is running.
No problems at all to my knowledge. It is all series looped with VERY short parallel drops to each device.
By the way, are the data bus errors supposed to show up in the event log or somewhere else?