Esp shield 8jst

ESP32 Shield

A custom-designed KiCad shield for the ESP32 DevKit V1 (30-pin) development board. This board serves as a central connectivity hub, breaking out GPIOs into secure JST connectors and providing dedicated interfacing for an ExpressLRS (ELRS) receiver. It is designed for robotics, RC vehicles, and telemetry applications.

Contents

Schematic & Board Layout Visuals

1. Subsystem Description & Working Principle
2. Pinout & Connector Reference
   • 1. Motor Driver Ports (4-Pin JST-XH)
   • 2. Consolidated Motor Ports (8-Pin JST-XH)
   • 3. RC Receiver Ports (ExpressLRS)
   • 4. Servo & Expansion Headers
   • 5. Extra GPIO Header Ports
   • 6. Power Input & Indicator
3. Hardware Design Warnings & Pin Conflicts
   • 1. Pin Resource Sharing Conflicts
   • 2. Input-Only Hardware Limitations
4. Software Pin Definitions (C++ / Arduino Header)
5. Assembly, Soldering & Manufacturing Guide
   • 1. Bill of Materials (BOM)
   • 2. Manual Rework Checklist (Revision 1.0 Boards)

Schematic & Board Layout Visuals

Schematic Screenshot

🎨 PCB Layout Layers

Top Layer	Bottom Layer	Silkscreen Layer

🎨 3D View

Subsystem Description & Working Principle

• Motor Driver Interfaces: Features seven dedicated 4-pin JST-XH connectors (J1 to J7) designed to interface with IBT-2 motor drivers. Each port delivers 5V, Ground, and two dedicated hardware PWM signals for independent, bi-directional control of up to 7 motors.
• Consolidated Cable Busses: Features two 8-pin JST-XH connectors (J13 and J14) that consolidate power, ground, and 6 PWM signals. These pins are internally bussed directly to 6 of the 7 motor ports, allowing a single 8-pin cable to handle multiple motor drivers and drastically reduce cable clutter.
• ExpressLRS Receiver Interface: Features two 4-pin JST-XH ports (J10 and J12) routed to the ESP32's hardware serial pins for ExpressLRS (ELRS) receivers.
• Logic Power Status LED: An onboard LED (D1) is tied directly to the ESP32's 3.3V rail via a current-limiting resistor (R2) to provide visual confirmation of active logic power.
• Noise Mitigation & Decoupling:
  • A 100µF capacitor (C1) on the 3.3V rail absorbs sudden current spikes, preventing accidental brownouts and system resets.
  • Smoothing capacitors (C2, C4, C7) are placed on power rails (like the ELRS 5V rail) to block motor-induced voltage ripples from interfering with critical RF control links.
• Power Protection: A Schottky diode (D3) is placed between the 5V terminal block input (J16) and the ESP32's VIN pin to act as a one-way safety valve. It blocks power from back-feeding into external supply rails when a USB cable is plugged in for programming, allowing safe flashing of code while the main battery or power supply is connected.

Pinout & Connector Reference

1. Motor Driver Ports (4-Pin JST-XH)

Each connector breaks out 5V, GND, and two PWM control signals (PWM A and PWM B) for bi-directional speed control.

2. Consolidated Motor Ports (8-Pin JST-XH)

These connectors bus the power, ground, and PWM signals of multiple motor channels into single headers to simplify wiring.

• J13 Consolidates Motors 1, 2, & 3:

  Pin 1	Pin 2	Pin 3	Pin 4	Pin 5	Pin 6	Pin 7	Pin 8
  GND	GPIO13 (M3_B)	GPIO27 (M3_A)	GPIO26 (M2_B)	GPIO25 (M2_A)	GPIO33 (M1_B)	GPIO32 (M1_A)	+5V

• J14 Consolidates Motors 5, 6, & 7:

  Pin 1	Pin 2	Pin 3	Pin 4	Pin 5	Pin 6	Pin 7	Pin 8
  GND	GPIO4 (M7_B)	GPIO16 (M7_A)	GPIO17 (M6_B)	GPIO18 (M6_A)	GPIO19 (M5_B)	GPIO21 (M5_A)	+5V

3. RC Receiver Ports (ExpressLRS)

Dedicated ports for ELRS receivers. Note the design details and limitations below:

4. Servo & Expansion Headers

Standard 3-pin servo headers (GND, 5V, Signal).

5. Extra GPIO Header Ports

Breakout headers for general-purpose expansion.

6. Power Input & Indicator

Power terminals and system indicator LEDs.

Hardware Design Warnings & Pin Conflicts

Before writing firmware or deploying the board, review these hardware bugs and resource conflicts:

1. Pin Resource Sharing Conflicts

[!IMPORTANT] To avoid hardware damage and signal contention, do not initialize conflicting peripherals in firmware:

• Motor 4 vs. Servos 1 & 3: J4 (Motor 4 control) shares GPIO23 with J17 (Servo 1) and GPIO22 with J19 (Servo 3).
• Motor 5 vs. Servo 2: J5 (Motor 5 control) shares GPIO21 with J11 (Servo 2).

2. Input-Only Hardware Limitations

[!NOTE]

• ESP32 GPIO34 and GPIO35 are hardware-level input-only pins.
• Since ELRS receiver ports (J10/J12) route to these pins, only receiver-to-ESP32 transmission (RX) is supported. The ESP32 cannot transmit data back to the receiver (TX is unconnected), meaning telemetry telemetry links are not supported on these ports.

Software Pin Definitions (C++ / Arduino Header)

Copy and paste this snippet into your project (pins.h) to quickly define the hardware mappings:

/**
 * @file pins.h
 * @brief Hardware pin mapping definitions for ESP32 Shield Rev 1.0.
 * @note Review the README for pin conflict and footprint routing warnings.
 */

#ifndef PINS_H
#define PINS_H

// ==========================================
// 1. Motor Drivers (IBT-2 PWM Signals)
// ==========================================
#define MOTOR1_PWM_A  32
#define MOTOR1_PWM_B  33

#define MOTOR2_PWM_A  25
#define MOTOR2_PWM_B  26

#define MOTOR3_PWM_A  27
#define MOTOR3_PWM_B  13

#define MOTOR4_PWM_A  23  // Shared with Servo 1
#define MOTOR4_PWM_B  22  // Shared with Servo 3

Assembly, Soldering & Manufacturing Guide

1. Bill of Materials (BOM)

2. Manual Rework Checklist (Revision 1.0 Boards)

Because of a manufacturing offset error and the lack of plated-through hole connectivity on this revision, perform the following assembly steps carefully:

[!CAUTION] 1. Copper Zone Clearance (Short Circuit Risk)

• During manufacturing, the top copper layer shifted slightly to the right. The copper ground fill is dangerously close to several component through-holes.
• Rework Action: Before soldering, inspect the board under magnification. Use an anti-cutter tool to scrape away overlapping copper around component leads that are close to the ground plane, and re-insulate the exposed areas with solder mask.

Reference Images:

Scraped Copper Corrected	Solder Mask Reapplied

[!IMPORTANT] 2. Double-Sided Solder Joints (Layer Bridging)

• The PCB does not have plated-through vias for components. It relies on the component leads themselves to bridge signals between the top and bottom copper layers.
• Solder Action: Solder the component pins on both the top and bottom sides of the PCB for:
  • C2, C4 (Decoupling Caps)
  • R2 (3.3V terminal)
  • D2 (Diode pins)

⚠️ CRITICAL: If you only solder the bottom side, the top copper traces will remain disconnected, breaking logic loops.

[!IMPORTANT] 3. Power & Ground Via Stitching

• All dedicated 5V and GND via holes must be manually bridged.
• Stitching Action: Feed a small piece of component lead wire or bus wire through each power and ground via hole, and solder it securely on both the top and bottom copper layers to form complete power loops.

🛡️ Protective Bottom Enclosure

A 3D-printable Bottom Enclosure (or Base Guard) is included in this repository to isolate the exposed underside of the PCB. It bolts directly to the bottom of the board with M3 screws, protecting the manual via stitches and through-hole pins from getting scraped, damaged, or accidentally shorted against conductive surfaces during operation.

📦 Download the 3D Model: Shield_Base_Guard.stl

3D CAD Render

Click to expand Gallery & Visual References

Physical Assembly (Top View)	Physical Assembly (Bottom View)	Physical Assembly (Side View)

🏭 Manufacturing & Production

If you want to manufacture this board yourself, all necessary production assets are pre-exported and located in the manufacturing_files/ directory:

• Top Layer PDF Top layer pdf – F. copper, F. Solder Mask, F. Silkscreen and Edge cuts is included in this pdf.
• Bottom Layer PDF Bottom layer pdf – B. copper, B. Solder Mask and Edge cuts is included in this pdf.

👤 Author

• Muhaimin Rahman - IUT EEE'23 - GitHub Profile

Editor

• safwansatil - IUT SWE' 23 - GitHub Profile