stm32

232 Articles

Cheetah 3d printer mobo

Cheetah MX4 Mini: A Pint-Sized 3D Printer Controller

December 28, 2025 by 28 Comments

There’s a seemingly unending list of modifications or upgrades you can make to a 3D printer. Most revolve around the mechanical side of things, many are simple prints or small add-ons. This upgrade is no small task: this 17-year-old hacker [Kai] took on designing and building his own 3D printer control motherboard, the Cheetah MX4 Mini.

He started the build by picking out the MCU to control everything. For that, he settled on the STM32H743, a fast chip with tons of support for all the protocols he could ask for, even as he was still nailing down the exact features to implement. For stepper drivers, [Kai] went with four TMC stepstick slots for silent motor control. There are provisions for sensorless homing and endstops, support for parallel and serial displays, and both USB-C and microSD card slots for receiving G-code. It can drive up to three fans as well as two high-amperage loads, such as for the heated bed.

All these features are packed into a board roughly the size of a drink coaster. Thanks to the STM32H743, the Cheetah MX4 Mini supports both Marlin and Klipper firmware, a smart choice that lets [Kai] leverage the massive amount of work that’s already gone into those projects.

One of the things that stood out about this project is the lengths to which [Kai] went to document what he did. Check out the day-by-day breakdown of the 86 hours that went into this build; reading through it is a fantastic learning aid for others. Thanks [JohnU] for sending in this tip! It’s great to see such an ambitious project not only taken on and accomplished, but documented along the way for others to learn from. This is a fantastic addition to the other 3D printer controllers we’ve seen.

Bare Metal STM32: Increasing The System Clock And Running Dhrystone

December 18, 2025 by 9 Comments

When you start an STM32 MCU with its default configuration, its CPU will tick along at a leisurely number of cycles on the order of 8 to 16 MHz, using the high-speed internal (HSI) clock source as a safe default to bootstrap from. After this phase, we are free to go wild with the system clock, as well as the various clock sources that are available beyond the HSI.

Increasing the system clock doesn’t just affect the CPU either, but also affects the MCU’s internal buses via its prescalers and with it the peripherals like timers on that bus. Hence it’s essential to understand the clock fabric of the target MCU. This article will focus on the general case of increasing the system clock on an STM32F103 MCU from the default to the maximum rated clock speed using the relevant registers, taking into account aspects like Flash wait states and the APB and AHB prescalers.

Although the Dhrystone benchmark is rather old-fashioned now, it’ll be used to demonstrate the difference that a faster CPU makes, as well as how complex accurately benchmarking is. Plus it’s just interesting to get an idea of how a lowly Cortex-M3 based MCU compares to a once top-of-the line Intel Pentium 90 CPU.

Continue reading “Bare Metal STM32: Increasing The System Clock And Running Dhrystone” →

A person's hand wearing a black glove is shown in the right part of the image, making a series of gestures. A representation of a hand mimics those motions on a laptop screen.

Weaving Circuits From Electronic Threads

October 6, 2025 by 6 Comments

Though threading is a old concept in computer science, and fabric computing has been a term for about thirty years, the terminology has so far been more metaphorical than strictly descriptive. [Cedric Honnet]’s FiberCircuits project, on the other hand, takes a much more literal to weaving technology “into the fabric of everyday life,” to borrow the phrase from [Mark Weiser]’s vision of computing which inspired this project. [Cedric] realized that some microcontrollers are small enough to fit into fibers no thicker than a strand of yarn, and used them to design these open-source threads of electronics (open-access paper).

The physical design of the FiberCircuits was inspired by LED filaments: a flexible PCB wrapped in a protective silicone coating, optionally with a protective layer of braiding surrounding it. There are two kinds of fiber: the main fiber and display fibers. The main fiber (1.5 mm wide) holds an STM32 microcontroller, a magnetometer, an accelerometer, and a GPIO pin to interface with external sensors or other fibers. The display fibers are thinner at only one millimeter, and hold an array of addressable LEDs. In testing, the fibers could withstand six Newtons of force and be bent ten thousand times without damage; fibers protected by braiding even survived 40 cycles in a washing machine without any damage. [Cedrik] notes that finding a PCB manufacturer that will make the thin traces required for this circuit board is a bit difficult, but if you’d like to give it a try, the design files are on GitHub.

[Cedrik] also showed off a few interesting applications of the thread, including a cyclist’s beanie with automatic integrated turn signals, a woven fitness tracker, and a glove that senses the wearer’s hand position; we’re sure the community can find many more uses. The fibers could be embroidered onto clothing, or embedded into woven or knitted fabrics. On the programming side, [Cedrik] ported support for this specific STM32 core to the Arduino ecosystem, and it’s now maintained upstream by the STM32duino project, which should make integration (metaphorically) seamless.

One area for future improvement is in power, which is currently supplied by small lithium batteries; it would be interesting to see an integration of this with power over skin. This might be a bit more robust, but it isn’t first knitted piece of electronics we’ve seen. Of course, rather than making wearables more unobtrusive, you can go in the opposite direction. Continue reading “Weaving Circuits From Electronic Threads” →

Franke A600 coffee machine with PicoVoice

Coffee By Command: The Speech2Touch Voice Hack

September 24, 2025 by 1 Comment

If you were to troll your colleagues, you can label your office coffee maker any day with a sticker that says ‘voice activated’. Now [edholmes2232] made it actually come true. With Speech2Touch, he grafts voice control onto a Franke A600 coffee machine using an STM32WB55 USB dongle and some clever firmware hacking.

The office coffee machine has been a suspect for hacking for years and years. Nearly 35 years ago, at Cambridge University, a webcam served a live view of the office coffee pot. It made sure nobody made the trip to the coffee pot for nothing. The funny, but in fact useless HTTP status 418 was brought to life to state that the addressed server using the protocol was in fact a teapot, in answer to its refusal to brew coffee. Enter this hack – that could help you to coffee by shouting from your desk – if only your arms were long enough to hold your coffee cup in place.

Back to the details. The machine itself doesn’t support USB keyboards, but does accept a USB mouse, most likely as a last resort in case the touchscreen becomes irresponsive. That loophole is enough: by emulating touchscreen HID packets instead of mouse movement, the hack avoids clunky cursors and delivers a slick ‘sci-fi’ experience. The STM32 listens through an INMP441 MEMS mic, hands speech recognition to Picovoice, and then translates voice commands straight into touch inputs. Next, simply speaking to it taps the buttons for you.

It’s a neat example of sidestepping SDK lock-in. No reverse-engineering of the machine’s firmware, no shady soldering inside. Instead, it’s USB-level mischief, modular enough that the same trick could power voice control on other touchscreen-only appliances.

Bare Metal STM32: The Various Real Time Clock Flavors

September 10, 2025 by 8 Comments

Keeping track of time is essential, even for microcontrollers, which is why a real-time clock (RTC) peripheral is a common feature in MCUs. In the case of the STM32 family there are three varieties of RTC peripherals, with the newest two creatively called ‘RTC2′ and RTC3’, to contrast them from the very basic and barebones RTC that debuted with the STM32F1 series.

Commonly experienced in the ubiquitous and often cloned STM32F103 MCU, this ‘RTC1’ features little more than a basic 32-bit counter alongside an alarm feature and a collection of battery-backed registers that requires you to do all of the heavy lifting of time and date keeping yourself. This is quite a contrast with the two rather similar successor RTC peripherals, which seem to insist on doing everything possible themselves – except offer you that basic counter – including giving you a full-blown calendar and today’s time with consideration for 12/24 hour format, DST and much more.

With such a wide gulf between RTC1 and its successors, this raises the question of how to best approach these from a low-level perspective.

Continue reading “Bare Metal STM32: The Various Real Time Clock Flavors” →

2025 One Hertz Challenge: STM32 Blinks In Under 50 Bytes

August 16, 2025 by 9 Comments

Many of us have run a Blink program on a microcontroller before. It’s effectively the “Hello, World!” of the embedded space. However, few of us have ever thought about optimizing our Blink code to be as miniscule as possible. But that’s precisely what [Rudra Lad] did for this entry into the 2025 One Hertz Challenge!

This example of Blink, delay_blinky_13, is built specifically for the STM32F4 Discovery microcontroller development board. [Rudra] notes the code is “highly optimized” and compiles down to a binary size of under 50 bytes. The code doesn’t even use RAM, and it aims to get the blink as close to 1 Hz as possible. Many optimizations were used to crunch it down as small as possible. For example, the standard startup code isn’t used, with the entire program instead written in the Reset_Handler to save space. Bit-band is also used to write to peripheral registers to blink the LED, since this uses less instructions than the typical methods. Meanwhile, with many tweaks to the delay counting routine, [Rudra] was eventually able to get the blink frequency to 1.00019 Hz, as measured on a logic analyzer. That’s pretty darn close!

While it’s rare that you have only 50 bytes of binary space to blink an LED, work like this is a great way to flex your coding muscles. Code is on Github for the curious, and if you’ve worked up your own impressive tiny binaries, don’t hesitate to let us know!

2025 Hackaday One Hertz Challenge

PCB Business Card Plays Pong, Attracts Employer

August 13, 2025 by 12 Comments

Facing the horrifying realization that he’s going to graduate soon, EE student [Colin Jackson] AKA [Electronics Guy] needed a business card. Not just any business card: a PCB business card. Not just any PCB business card: a PCB business card that can play pong.

[Colin] was heavily inspired by the card [Ben Eater] was handing out at OpenSauce last year, and openly admits to copying the button holder from it. We can’t blame him: the routed-out fingers to hold a lithium button cell were a great idea. The original idea, a 3D persistence-of-vision display, was a little too ambitious to fit on a business card, so [Colin] repurposed the 64 LED matrix and STM32 processor to play Pong. Aside from the LEDs and the microprocessor, it looks like the board has a shift register to handle all those outputs and a pair of surface-mount buttons.

Of course you can’t get two players on a business card, so the microprocessor is serving as the opponent. With only 64 LEDs, there’s no room for score-keeping — but apparently even the first, nonworking prototype was good enough to get [Colin] a job, so not only can we not complain, we offer our congratulations.

The video is a bit short on detail, but [Colin] promises a PCB-business card tutorial at a later date. If you can’t wait for that, or just want to see other hackers take on the same idea, take a gander at some of the entries to last year’s Business Card Challenge. Continue reading “PCB Business Card Plays Pong, Attracts Employer” →