Elk Bus Errors

 /Trouble Shooting the ELK M1 data bus

1. Make sure the RS-485 data bus is properly terminated. You should have the terminating jumpers at the extreme ends of the data bus. 

Example 1: Control and 1 keypad. Terminating resistor on the control and on the keypad.

Example 2: Control and two keypads with the keypads at the extreme ends of the data bus. Terminating resistor on each keypad. NO terminating resistor on the control.


2. Measure the bus resistance. Turn off all the power to the control with the ON/OFF switch. Using a Voltmeter set to the Ohms scale measure the resistance of the data bus across the A & B data terminals on the control. You should read 65 ohms +/- 10 ohms. If you read greater than 75 ohms, you do not have one of the terminating resistors in place. If you read less than 55 ohms, you have too many terminating resistors in place.

3. Set a unique address for each Keypad. All keypads come from the factory set to keypad address 1. Keypad 1 is always enrolled into the M1. You must set the address on any additional keypads. 

Hold the "*" and F5 key for approximately 5 seconds or until the setup screen appears. Press the F1 key for address setup. Use the UP and DOWN keys to set the address you want. Press the EXIT key twice to get out of the setup mode.
Note: You can calibrate the temperature sensor on the keypad by pressing the F2 key and using the UP and DOWN keys to display the desired temperature.

4. Press the ELK key, then 9 key. Enter the Installer Code (Factory default 172839). You should now be at menu 1 which enrolls and unenrolls all bus devices. Press the RIGHT arrow key. The keypad will momentarily lose communication while the M1 searchs all possible devices on the data bus. When the keypad LCD display returns, press the RIGHT arrow key to review all the devices that was found on the data bus. Make sure they have all been found. If not, try the enrollment again by pressing the ELK key to back up a menu then RIGHT arrow again.

5. If a device has not been found, make sure that ALL Data A wire connections connect to Data A on all bus devices and Data B connects to Data B on all bus devices. If any are swapped, the device will not work right.

6. Monitor the data bus errors. Press the ELK key then the 8 key. Press the RIGHT arrow key, enter a master code or Installer code. Press 6, for system diagnostics, then RIGHT arrow key. The keypad will now be displaying Data Bus Errors. If you can see the data bus errors counting up, there is still a bus problem. Note: It is normal to have an occasional data bus error.

Great to hear you got the data bus problem worked out. RS-485 data buss' can be a royal pain if not connected and terminated properly.

A good test on the data bus is to power down the system and measure the resistance across Data A and Data B on the RS-485 data bus. A properly terminated bus will measure about 65 ohms + or - 10 ohms.

Around 35 ohms means you have too many terminating resistors.

120 ohms means you only have one terminating resistor.

Greater than 1000 ohms means you have no terminating resistors.


An improperly terminated bus will show all kinds of weird operational problems. If you disconnect one module the problem will move to another module.

Watching data bus errors accumulate on the LCD screen menu 8,4 will show you the health of the data bus. No accumulation or less than 1 error per minute is good. If the errors are counting up as you watch the LCD screen, you have a data bus problem.

The data bus error accumulation count will be from the time you powered up the M1 Control. To reset the error count, power off the M1 and then back on.