Nakuja N4 Base Station PCB

This repository contains the hardware documentation for the Nakuja N4 rocket base station PCB.

At the moment, this folder includes PCB/schematic images, and firmware development is still underway.

Project Purpose

The board is designed as a base-station-side interface and telemetry/control platform for the Nakuja N4 rocket system.

• An ATmega MCU is used as the main I/O hub because of its large and flexible pin count.
• An ESP module is used for radio/telemetry-side communication.
• The user interface is provided through an LCD, keypad, and indicator LEDs.
• A servo output is provided for actuator/control use.
• Power is taken from an 8.4V input and stepped down to 5V and 3.3V rails.

Available Files

• schematic.png
• Screenshot 2026-02-23 075944.png

Design Links

• EasyEDA design: https://easyeda.com/editor#id=|16e8a1c5dba14926885ca769e663b6ae|140e3c6dc4e1411995634b5713806efc
• Nakuja Project: https://nakujaproject.com/

Confirmed Hardware

• Main MCU: ATmega2560
• Companion module: ESP32 (referred to as ESP34 in initial notes)
• Display: 20x4 I2C LCD
• Bluetooth: HC-05
• ESP-XBee interface: UART
• Servo power: not isolated from the board power distribution

System Overview

Main Controller: ATmega2560

The ATmega is the central controller in this design. It handles:

• LCD control
• Keypad scanning
• Indicator LED driving
• Bluetooth communication
• UART communication with the ESP32 (RX/TX)
• Servo signal output
• Battery-voltage measurement through a voltage divider

Communications Path

• ATmega2560 <-> ESP32: UART (RX/TX)
• ESP32 <-> XBee: UART serial interface for long-range telemetry path
• HC-05 <-> ATmega2560: UART serial interface for nearby wireless control/configuration

Telemetry flow is expected to be:

1. Rocket-side data is received over XBee at the base station.
2. ESP handles the wireless module interface.
3. ATmega handles UI/output/control logic and displays/interprets data.

User Interface

• 20x4 I2C LCD: displays telemetry/status/menu information over I2C.
• Keypad: user command and menu navigation input.
• Indicator LEDs: quick visual status/fault/arming indicators.

Actuation/Control

• Servo interface: PWM control signal generated from the ATmega2560.
• Servo power is currently non-isolated from the main board power rails.

Power Architecture

Input supply is 8.4V.

Power conversion and monitoring include:

• 5V buck converter for 5V devices/logic as needed.
• 3.3V buck converter for 3.3V devices (including ESP32/XBee-side peripherals where applicable).
• Voltage divider feeding an ATmega analog input to estimate battery voltage/percentage.

Connection Summary (Easy Reference)

Pin-level mapping is intentionally left to the schematic to avoid duplication. For exact pins and net names, refer to the schematic image and EasyEDA project link above.

Subsystem	Connected To	Interface Type	Notes
ATmega2560	20x4 I2C LCD	I2C	Display and menu output
ATmega2560	Keypad	GPIO matrix lines	Key scanning
ATmega2560	Indicator LEDs	GPIO digital outputs	Status signaling
ATmega2560	HC-05	UART (TX/RX)	Local wireless link
ATmega2560	ESP32	UART (TX/RX)	Inter-processor communication
ATmega2560	Servo	PWM output	Actuator/control output
ATmega2560	Battery sense divider	ADC input	Battery percentage estimation
ESP32	XBee module	UART	Telemetry radio interface
8.4V input	5V buck	Power conversion	5V rail generation
8.4V input	3.3V buck	Power conversion	3.3V rail generation

Firmware Status

Firmware is currently under development.

Planned firmware responsibilities include:

• Parsing telemetry and command packets
• Updating LCD pages and status indicators
• Managing keypad-driven user interaction
• Forwarding/bridging serial data between subsystems
• Battery monitoring and warning logic
• Servo command generation and safety constraints

Assumptions

• The ESP module is treated as an ESP32-class device.
• The 20x4 LCD is I2C-based (typical backpack interface, e.g., SDA/SCL + power).
• HC-05 and XBee are integrated through UART links as stated.
• Exact pin numbers are maintained in the schematic and are not duplicated here.

Current Hardware Status

• PCB and schematic images are present in this repository.
• Integration/firmware work is in progress.
• Pin-level software configuration will be documented as firmware matures.

Next Documentation Milestones

• Finalized pin map table (ATmega pins, ESP pins, LCD/keypad/LED assignments)
• Communication protocol notes (ATmega <-> ESP, ESP <-> XBee)
• Bring-up checklist and test procedure
• Firmware upload and build instructions

License