Decatur Makers Raspberry Pi RFID Wiegand Reader

The front (East) and side (welding pad / South) doors to Decatur Makers makerspace can be opened by active members with their RFID fob. These fobs are read by an ERK871 RFID reader, which sends both serial and Wiegand style data. We use 26 bit Wiegand fobs and read the Wiegand data/

Each door uses drastically different hardware aside from the RFID readers, but the same software (from this repository).

Hardware

• Version 1 - Front (East) door - 24V SDC LR100SGK latch retractor on a Sargent 20-series exit device (push bar)
• Version 2 - Side (South / welding pad) door - 12V HES 9600 630LBM electric strike used with a LSDA PD9000 rim exit device

rfidclient Daemon

rfidclient is a daemon written in Python that will start on boot and runs wiegand_rpi, waiting for this 10-digit number. It makes an HTTPS request to our "glue" server to check whether the fob number is valid, and if it is, sends 3V over GPIO pin 22 to the control input on the custom circuit board described above -- this closes the relay sending 24V to the door motor. The signal stays on for 5 sec.

The code for the back-end "glue" server is at https://github.com/DecaturMakers/glue/ (currently a private repo).

wiegand_rpi binary

When a fob is passed near the reader, wiegand_rpi interprets the 26 bit fob data and sends the digital "full code" of the fob, a 10-digit number with three leading zeroes, to stdout.

Compiling wiegand_rpi

A compiled wiegand_rpi binary is included in this repo at rfidclient/wiegand_rpi. Here's how to compile a new one if changes need to be made. It's probably easiest to do this on a physical Raspberry Pi.

Download and install the wiringpi .deb from the latest release at https://github.com/WiringPi/WiringPi/releases

Compile:

gcc wiegand_rpi.c -lwiringPi -lpthread -lrt  -Wall -o rfidclient/wiegand_rpi -O

rfid-prometheus Daemon

The rfidclient Daemon exposes a shared memory (shm) structure (see rfidclient/doorstate.py) with information about how long the process has been running, the number of authorized and unauthorized fob scans since start, and (if a latch contact pin is defined) the current state of the latch contact as well as the timestamps when it was last opened and closed. This information is exposed in a Prometheus-compatible format on port 8080.

Installing

If you did not compile on the same machine, first download the .deb package from the latest release at https://github.com/WiringPi/WiringPi/releases and install it.

Run the install script:

sudo make install

Then, fill out /etc/default/rfidclient with the https:// address of the glue server (a Decatur Makers-specific custom authorization server) and an authorization token.

The installation script will enable the rfidclient service so it starts at boot. To start the service immediately, run:

sudo systemctl start rfidclient.service

Note: At Decatur Makers, installation and configuration is currently managed via Puppet.

Configuration

Note: At Decatur Makers, installation and configuration is currently managed via Puppet.

This project is configured via environment variables set in /etc/default/rfidclient and loaded via dotenv. The currently-supported configuration options are as follows:

• GLUE_ENDPOINT str required - endpoint URL for the glue server.
• GLUE_TOKEN str required - auth token for the glue server.
• ZONE str required - Zone (door) name; used by the glue server and prometheus client.
• OUTPUT_PIN int optional; default: 22 - Output pin number to use for the strike/latch output; normally low, high when opening door.
• CONTACT_PIN int optional; default 0 means not used - Input pin number for latch position sensor, to determine if latch is currently open or closed. This pin should be normally closed, i.e. giving a value of 1 when the door is closed.
• CONTACT_TIMEOUT_MS int optional default 0 - Only valid if CONTACT_PIN is non-zero: how long (in ms) to keep latch/strike open after CONTACT_PIN turns off, before re-locking.