Compatibility

Firmware — McpIot Library

Board / Platform	Serial	WiFi TCP	Bluetooth	PWM	ADC
ESP32 (all variants)	✅	✅	✅ BLE Serial	✅	✅
ESP32-S2	✅	✅	❌	✅	✅
ESP32-S3	✅	✅	✅ BLE Serial	✅	✅
ESP32-C3	✅	✅	✅ BLE Serial	✅	✅
ESP8266 (NodeMCU)	✅	✅	❌	✅	✅
Arduino Uno (AVR)	✅	❌	❌	⚠️ limited pins	✅
Arduino Mega (AVR)	✅	❌	❌	⚠️ limited pins	✅
Arduino Nano	✅	❌	❌	⚠️ limited pins	✅
RP2040 (Pico)	✅	⚠️ Pico W	❌	✅	✅
STM32 (Arduino core)	✅	❌	❌	✅	✅

Legend: ✅ Fully supported · ⚠️ Partial / limited · ❌ Not available

All 4 pin types: digital_output, digital_input, pwm_output, adc_input
All 3 transports: Serial, WiFiClient, BluetoothSerial
pwm_write uses analogWrite (5 kHz default) — use custom LEDC tool for other frequencies
Up to 32 pins / 32 tools (configurable via MCP_MAX_PINS, MCP_MAX_TOOLS)

#define MCP_MAX_PINS  8
#define MCP_MAX_TOOLS 8

Feature	Status	Reason
Async / non-blocking I/O	❌	Arduino `loop()` is single-threaded
I2C built-in tools	❌	Use custom tools with your sensor library instead
SPI built-in tools	❌	Implement as custom tools
UART passthrough	❌	Out of scope
OTA firmware update	❌	Out of scope
JSON Schema: arrays, nested objects	❌	MCU RAM constraints
JSON Schema: `$ref`, `anyOf`, `allOf`	❌	Same reason
WebSocket transport	❌	Not in v1.0
mDNS / Zeroconf discovery	❌	Not in v1.0
String IDs in JSON-RPC `id` field	⚠️	Parsed as int; string IDs truncate to 0

Method	Format	Example
`SERIAL_PORT` env	port path	`SERIAL_PORT=/dev/ttyACM0`
`SERIAL_BAUD` env	baud rate	`SERIAL_BAUD=9600` (default: 115200)
`DEVICES` env	`id:port:baud` or `id:host:port:tcp`	`esp32:/dev/ttyUSB0:115200`

Feature	Status	Notes
Auto port detection	❌	Explicit config required in v1.0
Hot-plug reconnect	❌	Restart client to reconnect
BLE over Node.js	❌	Bluetooth only works over BluetoothSerial (Classic)
HTTP / SSE transport	❌	stdio only in v1.0
Nested Zod schemas	❌	Flat schemas only (mirrors firmware constraint)
Parallel requests to same device	⚠️	Works (ID matching), but no queue
Bun runtime	❌	Use Node.js instead