Pascal Wistinghausen's Raspberry Pi CM4-Powered Sigmoid S7P 3D Print Control Board Hits Kickstarter

This 3D printer control system aims to have just about as many features as you could possible need — all in one-and-a-bit boards.

Gareth Halfacree
22 days ago3D Printing

A new all-in-one control board for 3D printers, powered by a Raspberry Pi Compute Module 4 working in tandem with an STMicro STM32MPU1 microcontroller, is funding on Kickstarter: the Sigmoid S7P.

"Like its mathematical sibling the sigmoid curve, the Sigmoid S7P 3D printer control board connects the two control levels of modern hobbyists and enthusiasts 3D printers," claims embedded engineer Pascal Wistinghausen of the system he has developed. "A powerful real-time microcontroller for motion control, sensor interfacing and temperature management operating on a low abstraction level directly on the hardware and an even more powerful multicore application CPU providing high level programming options, user interfaces and advanced management functions."

The Sigmoid S7P 3D printer control board aims to have absolutely every feature you could need. (📹: Pascal Wistinghausen)

The all-in-one board features seven TMC2209 stepper drivers, four thermistor channels, eight end-stop channels, a 30A power MOSFET, two extruder heater channels, three power switches, three fan channels with speed monitoring, and a BLTouch connector. In addition to the STM32MPU1, which handles real-time control, the board includes a Raspberry Pi Compute Module 4 with HDMI, Camera Serial Interface (CSI), gigabit Ethernet, Wi-Fi, and four USB 2.0 ports.

Elsewhere in the design Wistinghausen has included an emergency-stop circuit implemented in hardware, a user controllable relay with both normally-open and normally-closed (NO and NC) contacts, a CAN bus channel, expansion connectors with UART, I2C, and SPI buses, and car fuses for power protection.

"When I first got the idea of an all integrated 3D printer control board the only option available were the Raspberry Pi Compute Modules in SODIMM format but I could not wrap my head around it so it was basically discarded before becoming a concept," Wistinghausen says of the project's origins.

"Then in 2019 I visited a workshop from ST about their all new STM32MPU1 and I was: Hey, this could actually work. I even started designing the hardware from scratch and then somebody with the same idea came and killed the project because the MPU was not powerful enough to run OctoPrint. So it was postponed again. But than came the release of the Raspberry Pi Compute Module 4 with its all new form factor and I was back on track because I knew it would not get better anytime soon. So I once again started working on it with a result I'm still absolutely amazed of."

Developed in partnership with the community which has sprung up around the Vor9on 3D printer, the Sigmoid S7P is said to "eradicate most compromises of the boards available today." Software support is largely universal, its creator claims, with Marlin, Klipper, OctoPrint, Mainsail, RepRapFirmware, and Duet Web Control included among the list of supported packages.

Wistinghausen is looking to raise funds for production via crowdfunding site Kickstarter, where the board is available to back with rewards starting at €220 (around $260 exc. shipping and taxes); the user is advised to supply their own Raspberry Pi Compute Module 4, or a model with Wi-Fi and 2GB of RAM can be selected as an add-on when backing.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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