Design Recommendations

Protocols

This page outlines our recommendations for open-source access control product standards. Specifically, we address physical and electrical interfaces.

Signalling Standards

• All new open-source access and security hardware should support legacy protocols such as Wiegand or clock-and-data as needed, due to the variety of devices available on the market.
• All newly developed panels or peripherals should support a bi-directional protocol.

Bi-Directional Protocol Standards

• Peripheral nodes such as door readers, sensor boards and keypads should support RS-485 or CAN bus. The advantages of CAN bus include support for message prioritization, a larger address space and support for more nodes, while RS-485 is simpler and many commercial devices already support it.

• Point-to-point serial over USB or RS-232 is acceptable for interface to a monitoring/control computer. Modern PCs have limited options for I/O, so any device that does not support Ethernet will most likely communicate with the PC either through an intermediate node or a serial USB/RS-232 connection.

• Controller nodes that have sufficient resources to run an IP stack should be connected via Ethernet, especially if a client/server authentication model is planned.

• For alerting and monitoring connections to the outside world, IP connectivity is going to have the fastest data rate and message delivery time of the above methods. A data-capable cellular device (GSM card or smartphone SDK interface) is an option for areas that lack connectivity or as a backup. POTS service via a serial modem is simple and robust, but lacking in functionality.

Physical Standards

• Standard RJ-45 connectors for all wired Ethernet applications
• Removable 3.5mm screw terminals for other hard-wired connections up to 5A
• Fixed or removable 5mm screw terminals for higher current power connections
• Anderson Power Pole connectors for battery and high-current DC power supply connections