The 4pi is a beautiful little 3d printer controller board.

It is 4 by pi inches in size, approximately 100x80mm.

4pi overview

It’s based on Atmel’s SAM3U processor, which runs on a 32-bit ARM Cortex-m3 core.

It includes 5 stepper drivers

each of which is built around an Allegro A4982. The board itself acts as a heatsink. They can handle up to about 1.9A per phase (the chip manufacturer claims 2A).

There is software current and microstepping control for each axis. Each motor driver is brought out to a screw terminal header.

There are 5 FET channels

One for the heatbed, two for your hotends, two for whatever you can think of.

The heatbed FET is rated for 12A continuous, but seems to manage up to 15A without heating up much. It’s brought out to a screw terminal header.

The hotend FETs are rated for 3A continuous, but can handle somewhat more. If you don’t use both at the same time, they have no problem with 5-6A. They are brought out to screw terminal headers.

The two extra fets are brought out to 0.1” headers so you can easily attach anything you like. They can handle at most 3A each.

Thermistors, endstops, and analog inputs

The 4pi board has 4 thermistor connections with a 4.7kOhm pullup on each. These are brought out to 0.1” headers.

There are six endstop connections, three of which can also be configured as extra analog inputs. All of these are also brought out to a 0.1” header.

Memory card reader

You can use any microSD-compatible memory card, and it will communicate with the processor at 25Mbits

Blinky lights

3 software controllable RGB LEDs are installed on the board to blind unsuspecting spectators indicate things.

High-speed USB

The microcontroller communicates with your computer at 480Mbits

Room for expansion

A great amount of expandability has been brought out onto the 0.1” headers along the edge.

3 SPI connections, an I2C connection, and a UART (serial) connection are brought out to the header next to the card reader socket. The same header had VMOT(main supply voltage), 3.3V and ground connections.

In addition, the header next to the USB port has 20 free GPIO pins as well as 5V(from USB), 3.3V and GND.


Firmware is in development at

Here are some additional photos (click for full size)

4pi overview 4pi overview 4pi overview 4pi overview

The fuse is included in the price. The MicroSD card is not.

The price is 168€.

This includes VAT for EU customers, and insured registered airmail shipping for everyone.

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