# ESP HomeKit Intercom

## Overview

An ESP32 HomeKit implementation of a [Lobby Door Intercom](https://wrt.nth.io/luke/siri-controlled-1970s-intercom-door)
with a solenoid door lock control and a voltage-based doorbell "buzzer".

This is a reimplementation of the [original based on a RaspberryPi Zero W and HAP-NodeJS](https://github.com/lukehoersten/homekit-door).

The impetus for this ESP32 implementation was [Espressif's HAP SDK](https://github.com/espressif/esp-homekit-sdk) which
is much better than the official [Apple "ADK"](https://github.com/espressif/esp-apple-homekit-adk).

## Electronics

The input voltage for the doorbell has a 23VDC and a 52VAC component and the same circuit is shared with all the units
in a teir. I haven't yet determined exactly how the buzzer indexes to the AC/DC voltage change but it's pulled
high. When the buzzer is triggered, the ADC measures a voltage drop of about 20%. I'm assuming this is the DC component
only measured by the ADC.

### AC

- 52V
- Peak 73V
- 100kO, 12.2kO
- Peak 8V
-

- f = 60 Hz
- C = 33 * 10^-6

4.7uF capacitor


### DC

- 23V
- HI (2.475V, 3.6V)
- LO (-0.3V, 0.825V)

- r1 = 100kO
- r2 = 10kO + 2.2kO

- 1.85V seems to be where high goes to low. - Probably remove the 2.2kO resister.

## Partition Sizing

When flashing, the following error may occur:

```
E (703) esp_image: Image length 1435760 doesn't fit in partition length 1048576
E (703) boot: Factory app partition is not bootable
E (705) boot: No bootable app partitions in the partition table
```

The fix is [documented](https://github.com/micropython/micropython-esp32/issues/235) as the following:

`esp-idf/components/partition_table/partitions_singleapp.csv`
```
# Name,   Type, SubType, Offset,  Size, Flags
# Note: if you have increased the bootloader size, make sure to update the offsets to avoid overlap
nvs,      data, nvs,     ,        0x6000,
phy_init, data, phy,     ,        0x1000,
factory,  app,  factory, ,        0x180000, # Change from 1M to 0x180000
```

## Doorbell ADC Output

An ESP32 GPIO pin cannot bt used for both interrupts and ADC sampling at the same time so two adjacent GPIO pins are bridged to take the same voltage, one for interrupt handling and the other to read the ADC.

```I (65813) HAP Intercom: Intercom bell ring value in range [2960]
I (66813) HAP Intercom: Intercom bell ring value in range [2966]
I (67813) HAP Intercom: Intercom bell ring value in range [2957]
I (68813) HAP Intercom: Intercom bell ring value in range [2945]
I (69813) HAP Intercom: Intercom bell ring value in range [2953]
I (70813) HAP Intercom: Intercom bell ring value in range [2951]
I (71813) HAP Intercom: Intercom bell ring value in range [2959]
I (72813) HAP Intercom: Intercom bell ring value in range [2930]
I (73813) HAP Intercom: Intercom bell ring value in range [2951]
I (74813) HAP Intercom: Intercom bell ring value in range [2960]
I (75813) HAP Intercom: Intercom bell ring value in range [2978]
I (76813) HAP Intercom: Intercom bell ring value in range [2987]
I (77813) HAP Intercom: Intercom bell ring value in range [2949]
I (78813) HAP Intercom: Intercom bell ring value in range [2951]
I (79813) HAP Intercom: Intercom bell ring value in range [2929]
I (80813) HAP Intercom: Intercom bell ring value in range [2961]
I (81813) HAP Intercom: Intercom bell ring value in range [2960]
I (82813) HAP Intercom: Intercom bell ring value in range [2953]
I (83813) HAP Intercom: Intercom bell ring value in range [2957]
I (84813) HAP Intercom: Intercom bell ring value in range [2957]
I (85813) HAP Intercom: Intercom bell ring value in range [2705]
I (86813) HAP Intercom: Intercom bell ring value in range [2343] ---- start
I (87813) HAP Intercom: Intercom bell ring value in range [2343]
I (88813) HAP Intercom: Intercom bell ring value in range [2359] ---- stop
I (89813) HAP Intercom: Intercom bell ring value in range [2909]
I (90813) HAP Intercom: Intercom bell ring value in range [3045]
I (91813) HAP Intercom: Intercom bell ring value in range [2951]
I (92813) HAP Intercom: Intercom bell ring value in range [2959]
I (93813) HAP Intercom: Intercom bell ring value in range [2951]
I (94813) HAP Intercom: Intercom bell ring value in range [2949]
```

## Building

Use the [Espressif esp-ide](https://docs.espressif.com/projects/esp-idf/en/latest/esp32/get-started/index.html#step-2-get-esp-idf) to build. This also includes a custom fork of the [Espressif HAP SDK](https://github.com/espressif/esp-homekit-sdk) that adds HomeKit doorbell support.