Open Supervised Device Protocol - OSDP
Current OSDP Specification - Version 2.1.6
Highlights of the specification and how it applies to everyday access control and security system installation challenges.
One of the biggest advantages to using OSDP to control and monitor devices in an access control application is the ease of implementation for programmers and system developers. Card read data is formatted in Wiegand, ABA, 200 bit binary, or raw format. Driving the LED and audible beeper in alternating patterns can be accomplished in one command. Polls and Responses ensure reliable supervision.
Scalable - Up to 126 addressable devices are allowed on one RS-485 line. However, it is more practical to split these up amongst several channels to reduce electrical loading and poll / response cycle times. 32 devices per line is a typical configuration.
Features - Since many diverse devices can be accommodated using OSDP, it is vital to solicit each device to gain a checklist of supported features. For instance if a single Red LED is the only visual indicator, then sending the "turn LED Blue" command would be meaningless. Each OSDP compliant device must support the Capability Report response.
Secure Channel mode defines a method of implementing encryption, key management, and authentication on an OSDP connection. Using AES-128 encryption and C-MAC chaining (see FIPS197), this method allows relatively easy implementation in control panels and peripheral devices. Even if writing in assembler.
Flexibility - Although many of the common functions a card reader / door interface would need to perform are well defined, a manufacturer specific command allows any unique function to be easily implemented. Uploading new firmware, configuring the device, etc.
The OSDP specification is meant to define a low cost means of implementing a standard 2-wire communications protocol. However, there is no limitation to using alternative media such as TCP/IP, Wireless, Fiber Optics, or any other half or full-duplex connection. Gateway products and protocol translators are readily available.