Tech on Sarah's Microblog

Sat, 22 Aug 2026 19:27:28 +0200

So anyways I started ~~blasting~~ redesigning.

Sat, 22 Aug 2026 19:03:10 +0200

Complete RE of the original Frekvens controller and LED matrix board.

Wed, 19 Aug 2026 18:01:38 +0200

The MCU on the controllerboard has the markings 89F112 000, which appears to be the CMS89F112 from Cmsemicon. It’s listed on jlc, for an estimated unit price of 0.3 USD. Hard to beat. The datasheet is in chineese, but looks to have

A 2K x 14 bit flash memory (I’m unfamiliar with the practicality of 14 bit memory?).
144 bytes of RAM.
Inbuilt ADC, comparators, timers, PWM outputs, buzzer driver and a sleep mode.
A voltage range of 1.8-5.5V (at 4MHz, or from 2.5V at 8MHz).

A very capable little device. 144 bytes of RAM is not a lot, a bitfield for the LED matrix would take up 32 bytes, almost a quarter of memory. Still, that is absolutely enough for more complex or interesting effects on the matrix, like iterative or dynamic animations. My claim still stands: TE’s embedded developers dropped the ball on this one.

Tue, 18 Aug 2026 23:49:39 +0200

Scans and sketch of the original circuit:

Cleaner sketch to follow…

Ikea Frekvens LED matrix modding

Mon, 17 Aug 2026 23:22:47 +0200

I found a couple of ikea frekvens LED matrix cubes from that teenage engineering collab in a thrift store in Vienna. They were cheap and I’d heard about people modding them. Plugged in, they provide possibly the most dissapointing lightshow I’ve seen:

The LED matrix cubes 'dancing' to sounds.

Download

Whatever electronics they’ve got in there, it’s doing a very simple job: Show a static frame of a pre-baked five frame looping animation. Monitor a microphone and progress the animation each time a loud sound occurs. Check two buttons on the back to turn the LEDs on or off, and switch between a few different animation sets.
That’s it. Nothing dynamic, nothing exciting. Why not make it just a bit more exciting?

Tue, 11 Aug 2026 21:34:22 +0200

Soldering a v1.1 board of the flying checklist project. Blaming my tools in the solder paste being way out of date and unrefrigerated. Reflow went surprisingly well though. No tombstones, one bridge, a few unconnected pads.

Sun, 09 Aug 2026 22:32:47 +0200

Found a 60x60 LED panel for 20dkk in the thrift store last week. Found an LED driver in the trash a couple days later. Just had to adjust the output power and change the power connector. Who knows, dali control might be broken, but I’m not living in an office. Think it’s gonna be my new work desk light.

Tue, 04 Aug 2026 22:55:31 +0200

Bought a couple of the AKY0477 batteries from TME and got them installed. There’s a bit of free space around the camera lens where extra cable can be tucked in.

Batteries replaced aaand.. it works perfectly.

Now what in the world can I use a little action cam for…? I also found the cage for it with a broken hinge. Maybe worth fixing.

Rollei Bullet HD actioncam with dead batteries

Tue, 04 Aug 2026 00:00:23 +0200

I found a Rollei action camera in the trash. Seems fully functional except it won’t take a charge. The shell clicks open after removing the four visible screws at each side of the camera. The camera has two lipo flat-packs wired in parallel and soldered to the board. Only one of the cells has a protection circuit, the other’s wired in behind it. Both cells have swollen significantly.