OSDP readers may interpret a non-driven 485-line as data. This results in a communication fault that inhibits the controller and reader from properly communicating.
To resolve: A pull-down 1 kΩ resistor is required on the controller so it can establish communication with OSDP readers. Refer to the table to determine if this applies. If the controller revision was implemented with the 1 kΩ resistor AND the firmware version matches or is greater than what is listed, 1 kΩ resistor does not need to be placed between the DAT/D0 & GND lines.
Access Controller | Assembly Revision (white sticker) | PCB Revision (printed on Panel Control Board) | Firmware Version |
|---|---|---|---|
LNL-1320 Series 3 | E | B | 3.21.1 |
LNL-1300 Series 3 | F | F | 3.21.1 |
LNL-X4420 | C | B | 1.27.1 |
LNL-X2220 | C | C | 1.27.1 |
LNL-X2210 | B | B | 1.27.1 |
If a pull-down resistor is required:
- Place a 1 kΩ resistor to pull down the DAT/DO to GND line. This is what creates a communication bias that keeps the reader from improperly interpreting the data.
- To function properly, there must be no ground faults in the installation.
- Make sure the DC Ground (power supply return) is not connected to the earth ground.
LNL-X2220 wiring with pull-down resistor
Related Topic
Secure communications
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