Imported from GitHub: enesasengineer/esp32-stm32-elrs-transmitter-pcb · commit d1b3ea8

Description

ESP32 + STM32 + E28 Transmitter Controller PCB Custom two-layer KiCad transmitter-controller PCB integrating ESP32 DevKit, STM32 Bluepill, dual joystick inputs, E28 2.4 GHz RF module interface, RF regulator headers, power switch, and debug test points.

README

ESP32 + STM32 + E28 Transmitter Controller PCB

Overview

This project is a custom two-layer transmitter-controller PCB designed for a prototype drone remote-control system. The board integrates an ESP32 DevKit, STM32 Bluepill, dual analog joystick inputs, an E28 2.4 GHz RF module, external RF regulator headers, power input, slide switch, and multiple debug test points.

The purpose of this PCB is to create a modular controller-core board that can be used as part of a custom drone electronics ecosystem. The design focuses on practical embedded hardware integration, low-cost PCB manufacturing, easy hand assembly, and accessible debugging.

Project Status

Stage	Status
Schematic design	Completed
PCB placement	Completed
PCB routing	Completed
Ground copper pour	Completed
DRC check	Completed / ready for final verification
Fabrication	Pending
Hardware bring-up	Pending
Field testing	Not claimed yet

This project is currently in the fabrication-ready prototype stage. It is intended to demonstrate PCB design, embedded hardware integration, RF module planning, and practical controller-board architecture.

Key Features

• ESP32 DevKit module socket
• STM32 Bluepill module socket
• Dual analog joystick module connectors
• E28 2.4 GHz RF module footprint
• RF regulator input/output headers
• Main power input connector
• PCB-mounted slide switch
• ESP32 5V jumper option
• RF test points
• GND test point
• DIO2 / DIO3 debug test points
• 2-layer FR-4 PCB design
• Prototype-friendly THT headers
• Ground copper pour
• RF antenna keep-out awareness

System Concept

The STM32 Bluepill can be used for joystick acquisition and low-level control processing. The ESP32 can be used for communication handling, system logic, or RF module control depending on firmware architecture.

Main Hardware Blocks

1. ESP32 DevKit Interface

The PCB includes two long socket rows for an ESP32 DevKit module:

• J_ESP32_L1
• J_ESP32_R1

The ESP32 module is socketed instead of permanently soldered, making it easier to replace, reprogram, or debug.

2. STM32 Bluepill Interface

The PCB includes two socket rows for an STM32 Bluepill module:

• J_BP_L1
• J_BP_R1

The Bluepill is intended to handle joystick-related embedded control tasks and communicate with the ESP32 through internal board routing.

3. Joystick Inputs

The PCB provides connectors for two analog joystick modules:

• J_JOY_L1
• J_JOY_R1

Each joystick connector is designed as a 5-pin 2.54 mm header.

Typical joystick signals:

Signal	Purpose
VCC	Joystick power
GND	Ground
VRx	X-axis analog output
VRy	Y-axis analog output
SW	Push-button switch output

4. E28 2.4 GHz RF Module

The PCB includes a footprint for an E28 2.4 GHz RF module.

Design considerations:

• RF module placed near the board edge
• Antenna keep-out area preserved
• RF-related test points included
• Dedicated RF regulator header path available
• Ground pour used around the RF area while respecting antenna clearance

5. RF Regulator Headers

The design uses external regulator input/output headers:

• J_RFREG_IN1
• J_RFREG_OUT1

This allows the RF module supply path to be separated and debugged independently.

6. Power Input and Switch

The PCB includes a main power input header and a slide switch.

PCB Label	Function
J_PWR_IN1	Main power input
SW1	Power path slide switch
JP_ESP32_5V1	ESP32 5V jumper option

The slide switch should be a straight PCB-mount THT type, not a 90-degree right-angle type.

Recommended switch rating:

Minimum: 0.5A @ 12V DC Preferred: 1A @ 12V DC

7. Test Points

The board includes several test points for debugging and validation:

Test Point	Purpose
TP1	General debug / power test point
TP_E28_DIO2	E28 DIO2 debug
TP_E28_DIO3	E28 DIO3 debug
TP_3V3_RF1	RF 3.3V rail test
TP_GND1	Ground reference test

PCB Design Notes

Design Item	Value / Approach
PCB type	2-layer FR-4
Connector pitch	2.54 mm
Assembly style	Mostly THT module sockets
RF module	SMD / castellated-style module area
Ground	Copper pour
Manufacturing target	Low-cost prototype PCB
Stencil	Not required for first prototype

Suggested PCB Manufacturing Settings

Parameter	Value
Layers	2
Material	FR-4
Thickness	1.6 mm
Copper	1 oz
Solder mask	Green
Surface finish	HASL
Stencil	Not required
Quantity	5 pcs

Bill of Materials

Component	Quantity	Notes
ESP32 DevKit / ESP32-WROOM-32 DevKit	1	Must match PCB socket width and pin count
STM32 Bluepill	1	Must match the 1x20 + 1x20 socket layout
E28 2.4 GHz RF module	1	Soldered to PCB RF area
AMS1117 3.3V regulator module	1	For RF regulator header path
Analog joystick module	2	Left and right joystick
2.4 GHz antenna	1	RF antenna
U.FL / IPEX to SMA pigtail	1	Required if the E28 module uses U.FL antenna output
Jumper cap 2.54 mm	2-3	Jumper headers
3-pin 2-position SPDT slide switch	1	Straight THT PCB type
100nF ceramic capacitor	2-3	RF rail decoupling
10uF capacitor	1-2	RF/regulator rail support
Test point / 1x01 header	5+	Debug test points

Important Component Notes

ESP32 DevKit Compatibility

ESP32 DevKit boards can have different physical widths and pin counts depending on manufacturer. The purchased ESP32 module must match the socket spacing and pin count used in the PCB footprint.

STM32 Bluepill Compatibility

The STM32 Bluepill module should match the standard dual-row 1x20 + 1x20 2.54 mm layout.

Slide Switch Compatibility

The slide switch footprint must be matched with the exact purchased part. The recommended type is: 3-pin 2-position SPDT ON-OFF or ON-ON usable depending on wiring Straight THT PCB-mount Not 90-degree right-angle Minimum 0.5A @ 12V DC Preferred 1A @ 12V DC

RF Module Assembly

The E28 RF module should be soldered carefully using flux and a fine soldering tip. The antenna area should remain clear of copper, components, and unnecessary routing according to the module placement strategy.