Apparently this idea is not new. However, this project makes the key holder a bit more intelligent.
Though the use of an ESP32 and HomeSpan the key hanger is connected to HomeKit. The device recognizes the state of all buttons on the device, and also which ports have something in them. "Something" in this case is one of six key chains.
The ESP32 that where used has only 4 analogue inputs and to outputs that can be used simultaneously with the Wifi-module. This could probably be expanded with something like an I2C-device, but in this project it was sufficient to use a multiplexer (74HC4052).
Through the multiplexer, the two outputs can be used to create 2x4 separate channels for the inputs to read. This means that each controller port and button can be iterated though and read independently.
The final circuit is shown in the schematic above. Each controller port is connected to the voltage supply (3,3V) at pin 0. Each key chain has a bridge between pin 0 and its respective key number. When plugged in, this gives a voltage drop over the controller port based on 5k resistance for pin (player) 1, 10k for pin 2 etc. I.e 5k*N where N is the player number.
To save a little bit on resistors these are connected in series as shown in the schematic.
Each player is connected to the respective pin on the multiplexer.
A similar approach, but much simpler is used for the buttons.
Each physical device (controller port or button) is represented by a class. These don't use the loop() provided by HomeSpan, but instead their measuring loop is controlled by the QueueMaster class. The QueueMaster class is responsible for switching the channel on the multiplexer (by setting the output pins LOW or HIGH) and telling the instances in the queue when their channel is active.
The queuer might have subscribers that they can inform about updates as needed.
The logic for the buttons is quite simple, since the queuer subscribes to itself. This is possible since there are no additional information we want to expose to HomeKit, other than the state of the physical button.
For the players, the logic is more complex. Each controllerPort might have any of the 6 key chains connected to it but we want to expose the players as OccupancySensors to HomeKit, and the controller ports as additional services within that OccupancySensor.
To distinguish between the two types of ControllerPort there is both a ControllerPort and a MeasuringControllerPort. The MeasuringControllerPort is the queuer and has a position in the queue corresponding to its port number. The ControllerPort represents the state of the physical port, but is published as sub-services to the OccupancySensor.
All Players are subscribers to the MeasuringControllerPort. When a Player (aka. key chain) is connected, removed or moved, the player updates the state of its OccupancySensor and the ControllerPorts accordingly.
The PCB was modded as described here. After the new components where soldered and connected, the inside of the device looked like this:
Top view of the assembled device.
More information about assembling, components and soldering are available here.
A mount was created to allow the device to hang straight on the wall. For this, a piece of oak was used:
The oak mount, shown at the side that will fasten to the FourScore
Follow the installation instructions here to get started with HomeSpan.
Select your board in the board selector. You might need to install the ESP32 board manager first. The board I'm using works with ESP32-WROOM-DA Module.
Set up the serial monitor with baud rate 115200.
Create a copy of ConfigExample.h and rename it to Config.h. Fill in the required information.
Use the upload command to send the code to the ESP32.