📖 ESP32 Coop Door Documentation

The goal is to document the setup & configuration of the esp32-coop project as well as the protocol in which the two devices communicate over BLE

📝 Summary:

• 📄 Project Overview: quick presentation of the mother project (goal, link device, protocol used, problematic)
• 📱 The App: how to get the it
• 🧰 Build instruction
  • 📋 Requirement
  • 🔦 Wiring
  • 🚀 First Boot
  • 🏠 3D file
• 📶 Communication protocol
  • 🔌 Run-down on how BLE works
  • 📊 The type of data required by the project (in progress)
  • 💻 Code snippet for each characteristic (in progress)

📄 Project Overview

The COOP-DOOR project aims to create an intelligent and user-friendly automatic coop door system. It empowers users to customize the door’s behavior based on specific conditions, such as time and light levels. To facilitate device management and monitoring, the project offers a mobile app.

The app enables users to track device and sensor health, as well as configure various operating conditions. For a demonstration of the project, please refer to the demo here. The core of the smart coop door relies on the ESP-32 platform, and the code repository can be found here.

This documentation page aims to guide users through the setup process, hardware requirements, and detailed workings of the system.

📱 App Installation

To install the app, follow these steps:

1. Visit coop-door.vercel.app using your mobile device’s web browser.
2. A small popup will prompt you to install the app. Tap “Install” to proceed.
3. Alternatively, if the popup doesn’t appear, you can manually add the app to your home screen by:
   • Tapping the three dots in Chrome.
   • Scrolling down and selecting “Add shortcut to home screen” or “Install app.”
4. The app will be installed on your device and accessible from the home screen.

Now, you can conveniently use the mobile app to monitor and control your coop door system, even without an internet connection.

🧰 Build instruction

Look out for instruction variations depending on the version of the project you’re building.

First of all, you will need to flash the firmware on the ESP32. Please refer to the instructions here. I do recommend unplugging the motor before flashing the firmware to avoid any connection problems caused by the encoder or any accidental movement of the powered motor.

📋 Requirement

This projet use :

• a ESP32 WEMOS lolin32 lite ( can be any esp32 with BLE),
  
• a H-Bridge l298n,
  
• a motor with a encoder,
  
• and a photoresistor

Additionally, you’ll need some basic items such as wires, soldering equipment (or soldering iron), and a 3D printer or woodworking tools, depending on your preferences.

Please note that you can easily swap out any component of this project for a similar one. It will most likely work out fine, but it may require some extra work. I would recommend it only to experienced thinkers.

🔌 Wiring

As illustrated below, follow these connections:

ESP32:

• Connect encoder signal to pin 2 (yellow) and pin 15 (green).
• Attach a resistor to pin 34 for analog value.
• Control the H-bridge with pins 27 (ENA), 26 (IN1), and 15 (IN2).

Remember to establish a ground connection between the H-bridge and the ESP32.

🚀 Initial Setup

Before Coop Installation:

It’s a good idea to run comprehensive tests before installing the device in the coop. Debugging is much easier and less frustrating when you’re comfortably situated in a well-ventilated room.

Initial ESP32 Boot:

When the ESP32 boots up initially, it assumes the door is closed. If that’s not the case, unplug either the motor or the ESP and manually close the door.

Proper Device Boot:

Now you can properly start up your device. Inside the app, go to settings and then to the door section. Set the number of rotations you want the motor to perform in order to open the door. Click the test button, and the motor will complete a full cycle (going up and then back down). Begin with a small rotation number, and gradually adjust it until you reach your desired door height.

Optimal Rotation Value:

Once you’ve figured out the best number of motor rotations, jot down this value along with the light sensor reading. To sync the ESP32’s time, head to the app’s home page and click on the time badge. A panel will appear, showing the time difference between your phone and the ESP32, along with a sync button.

Setting Conditions:

With that sorted, configure open and closing conditions in the door settings. Base these conditions solely on time, and set the door to stay open for the rest of the day.

Chicken Entry Time:

Return to the coop at the designated chicken entry time to check the light sensor value. If needed, adjust the closing condition within the app’s settings.

Autonomous Operation:

To enable autonomous operation, revisit the settings and door page. Click on ‘auto’ and then ‘apply’.

🪚 Casing Details

You can find the 3D model at this link, and the technical drawing is available //todo.

📶 Wireless comunication

📢 BLE Protocol

Each endpoint can have three properties: writable, readable, and notifyable.

• Writable: It allows the external user to write/edit the endpoint (officially called characteristic in BLE).
• Readable: It allows reading the characteristic’s value.
• Notifyable: It allows getting notified when that value is updated.

A byte is made out of 8 bits, and its value can go from 0 to 255.

To send the desired value in bytes, you must think it through:

• You will need to figure out the array size you will need and the function to convert it back and forth in C and in JS.

Currently, there are five communication subjects:

1. The light sensor (made out of 4 bytes).
2. The time (made out of 9 bytes, 8 to represent UNIX time and 1 to represent the UTC offset).
3. The closing condition
4. The opening condition
5. Door settings

💡 Data size

With BLE the goal is to send the smallest array posible

for each communication subjects i will justify each bytes and explain it’s encoding

1. The light sensor produces 4 bytes of data. Our objective is to transmit the current value, along with the minimum and maximum values recorded by the sensor. To achieve this, we need an additional variable called a “divider.” The maximum sensor value is fixed at 1024, while the highest value representable by a byte is 255.

   Calculating the divider is straightforward: we divide the maximum sensor value of 1024 by 255. This gives us the scaling factor needed for our encoding.

   With the divider in hand, we can create an encoded transmission as follows:

   • Current Value: current_value / divider
   • Minimum Value: min_value / divider
   • Maximum Value: max_value / divider
   • Unused Placeholder: (for the divider value)

   Reverting back to the original values is easy: simply multiply by the divider. This process maintains the integrity of the data throughout the encoding and decoding stages.

2. The time use 9 bytes The initial 8 bytes encode the UNIX time, while the ninth byte stores the user’s country time offset.

   Encoding UNIX Time: To encode the UNIX time:

   • Begin by taking the lowest 8 bits of the time value using a bitwise AND operation with 0xff.
   • Place this extracted value in the current byte of the array.
   • Divide the time value by 256 to discard the lowest 8 bits for the next step.

   Decoding UNIX Time: To decode the UNIX time:

   • Set up a variable to hold the decoded time value.
   • Iterate eight times (for each byte), starting from the most significant byte down to the least:
     • Multiply the current result by 256 (shift left by 8 bits) to make room for the next byte.
     • Add the value of the current byte to the result.

   Encoding Time Offset: Encoding the time offset is simple. You subtract the time offset from 12 and then add back 12 during decoding. This process is necessary because the time offset ranges from -12 to 12.

3. Door Condition use 4 bytes, used by both open condtion and closing condtion. We ne the following value: the door mode (checking for light or time), the threshold and finaly the time The array is form like this [door_mode, light_treshold / 4, time hour, time minutes] The door mode is represented by a single digit, reflecting various modes:

   • 0 : do nothing
   • 1 : change on light condition
   • 2 : change on time condition
   • 3 : change on light and time condition
   • 4 : change on light or time condition By adopting this array format and the corresponding door modes, we efficiently handle door conditions during both opening and closing situations.

4. Door settings use 2 bytes, with the following needed value the door mode and the number of turn.

   The door mode can take on various values:

   • 0: Door closed
   • 1: Door open
   • 2: Test door (opens and closes immediately)
   • 10: Automatic mode with the door closed
   • 11: Automatic mode with the door open

   Number of Turns Encoding: To encode the number of turns, we simply multiply the value by 10.

   Here’s the array structure for encoding: [door_mode, number_of_turns * 10].

⚙️ Code Snippette

Certainly, here’s your code snippet presented in a more readable manner:

Encoding and Decoding Long Numbers to Bytes

Here, we present functions for encoding and decoding long numbers into bytes. These functions are particularly relevant for working with the UNIX time standard. We provide the code snippets for both C and JavaScript:

C Implementation

byte* getBytesFromLong(long x) {
  byte* bytes = new byte[8];
  for (int i = 0; i < 8; i++) {
    bytes[i] = x & 0xff;
    x = (x - bytes[i]) / 256;
  }
  return bytes;
}

long getLongFromBytes(const byte* bytes) {
  long result = 0;
  for (int i = 7; i >= 0; i--) {
    result = (result * 256) + bytes[i];
  }
  return result;
}

JavaScript Implementation

export function getLongFromBytesBuffer(bytes) {
  let result = 0;
  for (let i = 7; i >= 0; i--) {
    result = result * 256 + bytes.getUint8(i);
  }
  return result;
}

export function getArrayFromBuffer(bytes, len) {
  let result = [];
  for (let i = 0; i < len; i++) {
    result.push(bytes.getUint8(i));
  }
  return result;
}

These functions offer efficient ways to convert long numbers to byte arrays and vice versa, which is particularly useful for working with the UNIX time standard. The C and JavaScript implementations cater to different programming environments, ensuring flexibility in usage.

Tutorial

Here is a video that explain how the BLE work //todo