In the DIY 3D printer community, most control boards are outfitted with a microcontroller and motor drivers to move the print head on multiple axis. The Arduino Mega is a popular microcontroller for 3D printing as it can handle RAMPS quite well, but enthusiast pkElectronics wanted something more versatile that could handle additional functionalities, such as Klipper, OctoPrint, and even webcam management. To that end, he decided to develop the all-in-one Sigmoid S7P control board, which packs a STM32MPU1 microcontroller, a TMC2209 stepper driver, and a Raspberry Pi Compute Module 4.
According to pkElectronics, the Sigmoid was designed using Autodesk Fusion 360 and packs many great features, including 4X thermistor channels, 8X endstop channels, power MOSFET, and a pair of heated extruder heads. It also features 3X power switches, 3X fan channels with tachometer, Wi-Fi, HDMI, 4X USB 2.0 ports, Gigabit Ethernet, and a pair of CSI ports for cameras.
“Generally speaking, everything is supported,” pkElectronics explains what software can be used with the Sigmoid. “I tested the connections required for the different Firmwares to the host prior to the PCB design with a Raspberry Pi 4 and an STM32F407 devboard. To flash the firmware, I use the integrated flash bootloader of the STM32 and added dedicated boot and reset lines between the MCU and the RPI. To support the STM32 port of RepRapFirmware and Duet Web Control, I also added an SPI bus connection between the MCU and the RPI.”
While pkElectronics has uploaded a detailed walkthrough of his Sigmoid S7P on his Hackaday project page, he is also considering mass producing the board if there’s enough interest.