Hardware reference

Complete hardware documentation for the ED1 Citilab Board Rev 2.3.

Board overview

The ED1 is an ESP32-based educational development board designed by Citilab Edutec. It integrates multiple peripherals for learning embedded systems and IoT development.

Specifications

Parameter	Value
MCU	ESP32-SIP (dual-core, 240MHz)
Flash	Integrated in SIP
RAM	520KB SRAM
WiFi	2.4GHz 802.11 b/g/n
Bluetooth	BLE 4.2
Power Input	USB-C (5V)
Battery	16340/CR123A Li-Ion (3.7V)
Dimensions	~80mm x 60mm

Block diagram

Components

Main controller

Component	Part Number	Description
U5	ESP32-SIP	Main MCU with integrated flash

Power management

Component	Part Number	Function	Notes
J1	105450-0101	USB-C Connector	Power + data
U2	NCP347	USB Overvoltage Protection	Protects against >5.5V
U1	MP2607DL-LF-Z	Li-Po Charger	1A charge rate, load sharing
IC1	PAM2401SCADJ	5V Buck-Boost	From battery to 5V
U9	ADP2108	3.3V Step-Down	System 3.3V rail
Q1, Q2	NMOS/PMOS	Battery Protection	Reverse polarity protection
BT1	16340/CR123A	Battery Holder	3.7V Li-Ion

Communication

Component	Part Number	Function	Notes
U6	CP2102N	USB to UART	Auto-programming support
ANT1	PRO-OB-440	2.4GHz Antenna	PCB antenna

Display

Component	Part Number	Interface	Notes
TFT1	TFT-Z144SN005	SPI	1.44” 128x128 ST7735
LED Matrix	WS2812X	GPIO12	32x8 (256 LEDs) external

Sensors

Ref	Part	Interface	Addr	Notes
U13	MXC6655XA	I2C	0x15	3-axis accelerometer
Q5	ALS-PT19-315C	ADC (GPIO34)	-	Light sensor
U12	TSOP75438TT	GPIO35	-	IR RX 38kHz; GPIO33 on Rev 1.0

Input/Output

Component	Part Number	Function	Notes
T1-T6	Capacitive pads	Touch buttons	6 buttons around display
SW1	JS102011SAQN	Power switch	Slide switch, no GPIO
SW2	PTS820	Reset button	Hardware reset
U11	MCP23009	I2C GPIO Expander	8 additional GPIO @ 0x20
U7, U8	ULN2004A	Stepper Drivers	For 28BYJ-48 motors
U10	PAM8301AAF	Audio Amplifier	For buzzer/speaker
Z1	MLT-8530	Buzzer	Driven by amplifier

Connectors

Connector	Type	Pins	Function
J2-J10	2.54mm Header	4	GPIO expansion
J11	Grove	4	I2C Grove connector
M1, M2	JST-XH	5	Stepper motor (28BYJ-48)

Stepper motor control

The ED1 board includes built-in support for two 28BYJ-48 stepper motors via the MCP23009 I2C GPIO expander and ULN2004A Darlington driver arrays.

Signal path

MCP23009 to motor pin mapping

GPIO	Signal	Driver	Motor	Coil
GP0	I2D	U8 pin 1	M2	D
GP1	I2C	U8 pin 2	M2	C
GP2	I2B	U8 pin 3	M2	B
GP3	I2A	U8 pin 4	M2	A
GP4	I1D	U7 pin 4	M1	D
GP5	I1C	U7 pin 3	M1	C
GP6	I1B	U7 pin 2	M1	B
GP7	I1A	U7 pin 1	M1	A

28BYJ-48 specifications

Step angle: 5.625° (64 steps per motor revolution)
Gear ratio: 64:1
Steps per output revolution: 512 (full-step mode) or 4096 (half-step mode)
Operating voltage: 5V DC
Drive method: Full-step sequence (4 phases) - matching MicroBlocks implementation

MCP23009 initialization

The MCP23009 requires specific register initialization for motor control:

Register	Address	Value	Purpose
IODIR	0x00	0x00	Set all 8 pins as outputs
GPPU	0x06	0xFF	Enable internal pull-ups (required!)
GPIO	0x09	varies	Motor coil patterns

Important: The GPPU register (pull-ups) must be enabled for reliable motor operation. Without this, the ULN2004A drivers may not receive proper signal levels.

Full-step sequence

The step sequence matches the MicroBlocks “ED1 Stepper Motor” library, which was used as the reference implementation. MicroBlocks is the official programming environment for the ED1 board. Source: MicroBlocks ED1 Library

Phase	Pattern	Motor 1 (upper nibble)	Motor 2 (lower nibble)
0	A+D	0x90	0x09
1	A+B	0xC0	0x0C
2	B+C	0x60	0x06
3	C+D	0x30	0x03

Timing: ~2ms between steps (1500µs in MicroBlocks)

ESPHome usage

Include the stepper package:

packages:
  stepper: !include packages/stepper.yaml

This exposes Home Assistant entities for controlling both motors:

Number entities: Set step count (-4096 to +4096) for precise positioning
Button entities: Quick rotation (CW/CCW 512 steps = full rotation)
Stop button: Immediately stop motors and power down coils

The package uses direct I2C register writes (not the ESPHome mcp23008 component) for reliable timing and compatibility with the MicroBlocks implementation.

Power system

Power sources

USB-C (5V): Primary power, also charges battery
Battery (3.7V): 16340/CR123A Li-Ion cell

Power rails

VBUS: Raw USB voltage (5V)
VDD_IN: After overvoltage protection
VBAT: Battery voltage (3.0-4.2V)
VDD5: Regulated 5V (from buck-boost)
VDD33: Regulated 3.3V (system rail)
VDD3A: Analog 3.3V (for ESP32)

Charging

Charge IC: MP2607DL with load sharing
Charge Rate: 1000mA (set by R6)
Status LEDs: STAT1, STAT2, DONE, CHR

Battery protection

When battery is inserted with wrong polarity, Q1 and Q2 transistors isolate the battery from the system, preventing damage.

Power switch (SW1)

The slide switch on the right side of the board (JS102011SAQN) connects/disconnects the battery from the power circuit. This is a purely mechanical switch with no GPIO connection.

Battery monitoring limitations

The ED1 board has no built-in battery monitoring capability. The following cannot be detected programmatically:

Feature	Status	Reason
Battery voltage	Not available	VBAT not connected to any ADC pin
Charging status	Not available	STAT1/STAT2 only connected to LEDs
USB connected	Not available	VBUS not connected to any GPIO
Power switch state	Not available	Switch is mechanical only

The charger status signals (STAT1, STAT2, DONE, CHR) from the MP2607DL are routed only to LED drivers (NL7SZ97), not to ESP32 GPIOs.

Hardware modification for battery monitoring

To read battery voltage, add an external voltage divider to an analog expansion port: This divides the 3.0-4.2V battery range to ~1.5-2.1V, safe for the ESP32 ADC. ESPHome configuration:

sensor:
  - platform: adc
    pin: GPIO36
    name: "Battery Voltage"
    attenuation: 11db
    filters:
      - multiply: 2.0 # Compensate for voltage divider
    update_interval: 60s

Datasheets

Component datasheets are included in docs/datasheets/:

Hardware revisions

This documentation primarily covers ED1 Rev 2.3, but packages have been tested on both revisions.

Revision differences

Component	Rev 1.0	Rev 2.3
Accelerometer	LIS3DH (0x19)	MXC6655XA (0x15)
I/O Expander	MCP23017 (0x20)	MCP23009 (0x20)
Stepper Driver ICs	ULN2004A	ULN2004A
IR Emitter	GPIO32 (Untested)	Not available
IR Receiver	GPIO33	GPIO35 (Tested OK)

Compatibility notes

Core packages (display, buttons, sensors, buzzer, etc.) work on both revisions.
Stepper package (packages/stepper.yaml) is designed for Rev 2.3’s MCP23009.
IR Features:
- Rev 2.3: Receiver works reliably on GPIO35. No emitter hardware.
- Rev 1.0: Receiver on GPIO33, emitter on GPIO32 (both untested in this project).
Accelerometer is not yet implemented in ESPHome packages

Identifying your revision

Check the I2C scan on boot (in ESPHome logs):

0x15 + 0x20 = Rev 2.3 (MXC6655XA + MCP23009)
0x19 + 0x20 = Rev 1.0 (LIS3DH + MCP23017)

The original KiCad design files and full schematics are available from Citilab.

Getting started

Hardware

ESPHome

Project

Hardware reference

Board overview

Specifications

Block diagram

Components

Main controller

Power management

Communication

Display

Sensors

Input/Output

Connectors

Stepper motor control

Signal path

MCP23009 to motor pin mapping

28BYJ-48 specifications

MCP23009 initialization

Full-step sequence

ESPHome usage

Power system

Power sources

Power rails

Charging

Battery protection

Power switch (SW1)

Battery monitoring limitations

Hardware modification for battery monitoring

Datasheets

Hardware revisions

Revision differences

Compatibility notes

Identifying your revision

​Board overview

​Specifications

​Block diagram

​Components

​Main controller

​Power management

​Communication

​Display

​Sensors

​Input/Output

​Connectors

​Stepper motor control

​Signal path

​MCP23009 to motor pin mapping

​28BYJ-48 specifications

​MCP23009 initialization

​Full-step sequence

​ESPHome usage

​Power system

​Power sources

​Power rails

​Charging

​Battery protection

​Power switch (SW1)

​Battery monitoring limitations

​Hardware modification for battery monitoring

​Datasheets

​Hardware revisions

​Revision differences

​Compatibility notes

​Identifying your revision

Board overview

Specifications

Block diagram

Components

Main controller

Power management

Communication

Display

Sensors

Input/Output

Connectors

Stepper motor control

Signal path

MCP23009 to motor pin mapping

28BYJ-48 specifications

MCP23009 initialization

Full-step sequence

ESPHome usage

Power system

Power sources

Power rails

Charging

Battery protection

Power switch (SW1)

Battery monitoring limitations

Hardware modification for battery monitoring

Datasheets

Hardware revisions

Revision differences

Compatibility notes

Identifying your revision