=========================
Electronics Assembly
=========================

Overview
========
Now that the **Evolutronix GUI** and the **state machine** firmware have been successfully uploaded to the ESP32, we can proceed with connecting the electronics.  
This section covers how to power the servos, connect the **PCA9685 servo driver**, and safely verify the setup before motion testing.

Power Supply and Voltage Regulation
===================================
The servo motors require an external power source. We use a **LiPo battery** connected to a **LM2596 voltage regulator** to step down the voltage to a stable **6V output**.

1. Connect the LiPo battery to the input terminals of the **LM2596**.  
2. Using a multimeter, verify the output voltage on the LM2596 before connecting any components.  
3. Adjust the output voltage:
   - Turn the potentiometer **counter-clockwise** to decrease voltage.
   - Turn **clockwise** to increase voltage.
4. When the output reads **6.0V**, it is ready to power the PCA9685 servo controller.

Once confirmed, connect the LM2596 output to the **V+ and GND terminals** on the PCA9685 board.  
Make sure that the **ESP32** continues to draw its power from the **USB connection** during setup.

.. warning::
   ⚠️ **Critical Polarity Check:**  
   Always verify that the **positive (V+)** and **negative (GND)** wires are connected to the correct terminals.  
   Reversed polarity will **irreversibly damage** the PCA9685 board.

.. figure:: ../images/electronics/LM2596A.png
   :alt: Wiring diagram of ESP32, LM2596, and PCA9685
   :align: center
   :width: 50%

   *Figure 1 – LM2596.*

Connecting the evolutronix breadboard
=====================================
With the power system ready, we can now connect and test the servos.


.. figure:: ../images/electronics/connection.png
   :alt: Wiring diagram of ESP32, LM2596, and PCA9685
   :align: center
   :width: 70%

   *Figure 2 – Wiring overview of the power distribution.* 

Connecting and Centering the Servos
===================================
With the power system ready, we can now connect and test the servos.

1. Connect a single servo to **channel 0** on the PCA9685.
2. Ensure that:
   - The ESP32 is connected to your PC via USB.
   - The **Evolutronix GUI** is open and communicating with the ESP32.

Turn on the LiPo power supply.  
From the GUI, gently move the slider corresponding to the connected servo.  
You should see the **servo horn** respond smoothly to the movement command.

If the servo responds correctly, the communication between the ESP32, PCA9685, and GUI is confirmed.

Centering Procedure
--------------------
Next, we need to **center each servo** before installing the servo horns.

1. Use the GUI to move each servo to its **center position** (typically 90°).  
2. Power off the system temporarily.  
3. Mount the **servo horn** so it aligns symmetrically with the robot’s neutral stance.  
4. Repeat for all servos.

.. note::
   Make sure to keep track of which servo corresponds to which joint or limb.  
   Consistent channel mapping will simplify later motion testing and debugging.

.. figure:: ../images/servo_centering.png
   :alt: Centering a servo before attaching horn
   :align: center
   :width: 60%

   *Figure 2 – Centering servos using the Evolutronix GUI.*

Testing the Sequence Loop
=========================
After all servos are centered and horns attached, we can verify motion sequences.

1. Open the **Evolutronix GUI** and set servo parameters as follows:

   - **Servo 0:** Position = 30°, Speed = 5  
   - **Servo 1:** Position = 45°, Speed = 3

2. Save these positions as a **sequence**.
3. Move the servos to a different position (for example, 60°).
4. Save again as the next sequence step.

Once the sequence is defined, you can play it using:

.. code-block:: text

   <LOOP,1>
   <START>

The ESP32 will now run the stored sequence, cycling through the programmed positions at the specified speeds.

.. figure:: ../images/gui_sequence_run.png
   :alt: Running a servo sequence loop
   :align: center
   :width: 70%

   *Figure 3 – Executing a stored motion sequence.*

Shutdown Procedure
==================
When testing is complete:

1. Power down the LiPo battery first.
2. Disconnect the servos from the PCA9685.
3. Note the channel assignments (e.g., servo 0 = front left leg joint 1).
4. Store your configuration for future calibration.

.. tip::
   During initial calibration, avoid mechanical load or obstacles near the servos.  
   This prevents unexpected overcurrent draw or gear stress during startup.

Summary
========
You have now:

- Assembled the power supply and verified safe voltage output  
- Connected and tested servo communication via the Evolutronix GUI  
- Centered all servo horns  
- Executed and validated a basic motion sequence  

The next chapter will describe the **mechanical assembly** and structural alignment of the robot frame.