Data bus termination debugging.

[project_x]

I have been setting up my Elk M1 system. So far, I have one keypad connected, can connect with ElkRP over serial port.
I then connected a M1XIN 16-zone expander to the RS-485 bus, address 2. I would get 3blinks on the board led. I switched to address 3 and got 5 blinks. When I try to enroll, both from the keypad or elkrp, it fails. I check continuity of the cables no problem. Keypad is terminated, M1XIN board is terminated. JP3 on the Elk is not jumped.

I tried using a 8 relay board, same symptons, so I suspect the bus, either termination or connection.
Can someone point me in the right direction to trouble shoot this?

Thanks,
Rob

 

[Digger]

Double check the polarity of the databus wires. I have seen this happen a few times.

 

[project_x]

A is connected to A
B is connected to B

what should the resistance across A&B if I have both data buses terminated?

 

[project_x]

I figure it out, when I was checking continuity, my multimeter was touching the wire on the A data line, but the wire was not screwed in properly. Once connected, it works great : )