Hardware Compatibility

LadderIDE offers twenty boards. They differ in three ways that matter before you buy one: whether you can build for it offline, whether it has been run on real hardware by us, and whether its pins are 5 V or 3.3 V.

The short version

• Arduino Uno, Nano, Mega — everything needed to compile and upload is in the installer. No internet, no downloads, no account. Start here if you are choosing your first board.
• Every other board downloads its board support once, the first time you compile for it. LadderIDE offers the download and installs it for you.
• 3.3 V boards are not 5 V tolerant. Nucleo, Pico, Teensy, ESP32 and ESP8266 will be damaged by a 5 V input. Check before wiring a switch to a pin.

Boards

Bundled means the board support ships inside the installer, so the board compiles with no internet connection.

Verified means a LadderIDE-generated sketch has been compiled, uploaded and run on the physical board. Everything else compiles cleanly and is expected to work, but we have not put one on a bench — which is a statement about our testing, not a known fault.

Board	Core	Logic	SRAM	Bundled	Verified
Arduino Uno	arduino:avr	5 V	2 KB	Yes	Yes
Arduino Nano	arduino:avr	5 V	2 KB	Yes	—
Arduino Mega 2560	arduino:avr	5 V	8 KB	Yes	Yes
Arduino Pro Mini	arduino:avr	5 V	2 KB	Yes	—
Arduino Leonardo	arduino:avr	5 V	2.5 KB	Yes	—
Arduino Micro	arduino:avr	5 V	2.5 KB	Yes	—
Arduino Nano Every	arduino:megaavr	5 V	6 KB	—	Yes
Arduino Due	arduino:sam	3.3 V	96 KB	—	—
Arduino MKR WiFi 1010	arduino:samd	3.3 V	32 KB	—	—
Arduino Nano 33 IoT	arduino:samd	3.3 V	32 KB	—	—
ST Nucleo-64 F401RE	STMicroelectronics:stm32	3.3 V	96 KB	—	—
ST Nucleo-64 F446RE	STMicroelectronics:stm32	3.3 V	128 KB	—	Yes
Raspberry Pi Pico	rp2040:rp2040	3.3 V	264 KB	—	—
Raspberry Pi Pico W	rp2040:rp2040	3.3 V	264 KB	—	—
Raspberry Pi Pico 2	rp2040:rp2040	3.3 V	520 KB	—	Yes
Raspberry Pi Pico 2 W	rp2040:rp2040	3.3 V	520 KB	—	—
Teensy 4.0	teensy:avr	3.3 V	1 MB	—	Yes
Teensy 4.1	teensy:avr	3.3 V	1 MB	—	—
ESP32 Dev Module	esp32:esp32	3.3 V	320 KB	—	—
ESP8266 (NodeMCU)	esp8266:esp8266	3.3 V	80 KB	—	—

Memory is the real limit on an Uno

An Uno has 2 KB of SRAM, and your tags, timers and message buffers live in it. A large program with many monitored tags can run out — the compiler will tell you, and the Output pane reports the percentage used after every build. If you are over about 80 %, the usual causes are a large number of referenced tags or a big message buffer, not the number of rungs.

A Mega (8 KB) or any 32-bit board removes the ceiling entirely. Nothing about your program has to change to move it — pick the new board in Board Config and compile again, and the pin labels follow the new layout.

The serial pins

On most boards D0 and D1 carry the Get Online link and can never be used as ladder I/O. LadderIDE marks them reserved in the Pin Map and refuses to compile a program that uses them.

Boards with native USB are the exception. On a Teensy or a Pico, Get Online rides the USB port itself, so every header pin stays free for your logic. Those boards also provide no serial port until their first upload, which is expected rather than broken — see No ports detected.

Ethernet and fieldbus

Ethernet needs a shield or module — a W5100 or W5500 controller over SPI. These combinations have been verified on real hardware against real equipment:

Combination	Verified
Mega 2560 + W5100 shield	EtherNet/IP server and client, against a CompactLogix L23E
Mega 2560 + Ethernet Shield 2 (W5500)	EtherNet/IP and Modbus TCP servers
Nucleo F446RE + Ethernet Shield 2 (W5500)	EtherNet/IP and Modbus TCP, server and client
Uno + RS-485 shield	Modbus RTU master, against an AutomationDirect CLICK

Other board-and-shield combinations compile, and are not in this list only because they have not been put on a bench.

Two hardware notes worth having before you order parts:

• An SPI Ethernet module claims the SPI bus pins. On a board where the on-board LED shares SCK — the Nucleo’s D13, for instance — you cannot also use that pin as a ladder output while the shield is attached. LadderIDE checks this and reports it as a pin collision rather than letting it fail quietly.
• Clone W5500 modules are a real risk. Several we bought were defective in ways that look like a software fault: the chip answers, reports its version, and even replies to a ping, while its socket engine never opens a connection. Buy a genuine Ethernet Shield 2 if you can.

Choosing a first board

An Arduino Uno is the right first board for almost everyone: it is the cheapest, it needs no downloads, its 5 V pins survive wiring mistakes that would destroy a 3.3 V board, and every bundled example targets it.

Move up when something specific pushes you: a Mega when you run out of pins or memory, a Nucleo F446RE when you want Ethernet and a PLC to talk to, a Teensy 4.x when you want speed. Your program moves with you.