2 relay switches (250V / 10A, controlled via HTTP POST to the board)
2 opto-isolated digital inputs (110VAC-240VAC, state pushed from board to HA via webhook)
NFC/PN532 card reader for access control (optional, via UEXT connector)
No polling — fully event-driven for inputs, command-driven for relays

Installation

Copy custom_components/olimex_esp32_c5 into your Home Assistant config/custom_components/ directory and restart HA.

`esp32_arduino`

Arduino sketch for the ESP32-C5-EVB board.

Hosts a REST API on port 80
Registers a callback URL with HA on startup
POSTs input state changes to HA webhook in real time
Optional NFC card reader integration for relay trigger automation

Arduino IDE Settings

Setting	Value
Board	ESP32C5 Dev Module
Flash Size	4MB
USB CDC On Boot	Enabled

See esp32_arduino/DEPLOYMENT_GUIDE.md for full flashing instructions.

Key Differences from C6-EVB

Feature	C6-EVB	C5-EVB
Relays	4	2 (250V / 10A)
Inputs	4	2 (opto-isolated 110VAC-240VAC)
Relay 1	GPIO 10	GPIO 24
Relay 2	GPIO 11	GPIO 23
Input 1	GPIO 1	GPIO 4
Input 2	GPIO 2	GPIO 5
LED	GPIO 8	GPIO 27
Button	GPIO 9	GPIO 28
NFC UART	GPIO 4/5 (UEXT1)	GPIO 26/25 (UEXT)

Hardware Overview

Pin Configuration

Relays (250V / 10A AC/DC)

Relay 1: GPIO24
Relay 2: GPIO23

Opto-Isolated Inputs (110VAC-240VAC)

Opto Input 1: GPIO4
Opto Input 2: GPIO5

LED & Button

User LED: GPIO27 (active LOW)
User Button: GPIO28 (active LOW, internal pull-up)

UEXT Connector (for NFC reader / additional peripherals)

I2C: SDA=GPIO9, SCL=GPIO8
UART: TX=GPIO26, RX=GPIO25
SPI: CLK=GPIO2, MOSI=GPIO7, MISO=GPIO6

Power & Connectivity

USB-C power input
WiFi 6 (802.11ax) dual-band (2.4 & 5 GHz)
Bluetooth 5.0 LE
Zigbee & Thread capable

API Endpoints

Status & Control

GET /api/status — Returns all relay and input states (JSON)
POST /relay/on?relay=1-2 — Turn relay on
POST /relay/off?relay=1-2 — Turn relay off
GET /relay/status?relay=1-2 — Get relay state

Inputs

GET /input/status?input=1-2 — Get input state

LED

POST /led/on — Turn LED on
POST /led/off — Turn LED off

Home Assistant Integration

POST /register?callback_url=... — Register HA webhook (no auth required for bootstrap)

NFC Access Control

GET /nfc/status — Get NFC module status
GET /nfc/config — Get NFC access control settings
POST /nfc/config?auth_uid=...&relay=1-2&pulse_ms=5000 — Set NFC access config
POST /nfc/enable?state=0|1 — Enable/disable NFC module

Debug

GET /debug — System info (requires basic auth)

All endpoints except /register require Basic HTTP Authentication (default: admin/admin) or HMAC-SHA256 request signing.

Setup Instructions

Flash the firmware
- See DEPLOYMENT_GUIDE.md
Configure WiFi
- Edit WiFi credentials in esp32_arduino.ino (lines ~58-59)
- Set a static IP (currently 192.168.0.240)
- Flash the board
Add to Home Assistant
- Copy custom_components/olimex_esp32_c5/ to ~/.homeassistant/custom_components/
- Restart Home Assistant
- Settings → Devices & Services → Create Integration → Olimex ESP32-C5-EVB
- Enter board IP, port (80), and Home Assistant callback IP
Optional: NFC Card Reader Setup
- Attach PN532 breakout to UEXT connector (TX=GPIO26, RX=GPIO25)
- Open board web UI (http://<ip>/)
- Enable NFC module
- Scan a card to authorize it
- Configure trigger relay and timeout

Home Assistant Integration

Once configured, entities appear automatically:

Switches

switch.olimex_esp32_c5_relay_1
switch.olimex_esp32_c5_relay_2

Binary Sensors

binary_sensor.olimex_esp32_c5_input_1 (opto-isolated input)
binary_sensor.olimex_esp32_c5_input_2 (opto-isolated input)
binary_sensor.olimex_esp32_c5_nfc_card (NFC card present, if enabled)

Automations Create automations to trigger relays on input events, NFC cards, time schedules, etc.

Troubleshooting

Board not reachable

Check WiFi SSID and password in code
Verify board IP with serial console output
Check firewall allows port 80

Inputs not triggering

Verify wiring to opto-isolated inputs (GPIO4, GPIO5)
Use /debug endpoint to check input state
Ensure Home Assistant callback URL is registered

NFC not detecting cards

Check PN532 wiring (TX=GPIO26, RX=GPIO25)
Set PN532 DIP switches to HSU mode (both = 0)
Check serial output for PN532 detection message
Try different baud rates (115200, 9600, 57600, 38400)

Security Notes

Default credentials: admin / admin
Change WEB_PASSWORD in secrets.h before deployment
Enable API_SECRET for HMAC-SHA256 request signing (optional)
Only expose board on trusted local networks
NFC cards trigger relays when authenticated card is present

License & Attribution

Hardware: Olimex
Firmware: Arduino & ESP-IDF
Integration: Home Assistant Custom Component