I was too late, but on the plus side, I already received them today and they are 128k (at least one of the five-pack 
3 Likes
Excellent. Hopefully the rest also work out for you.
1 Like
Im in the US, do you have any more 128k blue pills left?
Is there any documentation to add an octave knob to the braids like on the performance VCOās?
1 Like
You could use one of these:
https://www.elby-designs.com/webtek/synth-modules/octave/octave.htm
The designs there use SMD components but you could build one on stripboard with through hole parts. Resistors on the switch (R101āR108 in the 5U design, R2-R5 in the 3U) and op amp input and feedback resistors (R110 and R112 or R7 and R9) should be matched at the 0.1% level.
If you donāt need to add a bias voltage you could omit everything downstream of the buffer (U101A or U1A).
Wire the output through a 100k resistor to IC9 pin 13. That resistor should be matched to R54.
4 Likes
I donāt know whether the noise issues are related to replacing the C24 capacitor with a polarized one, but typically non-polarized electrolytic capacitors can be substituted by connecting two polarized capacitors of the same value, i.e. you could join two polarized 10Ī¼F by soldering their negative (or positive) leads together and soldering the remaining two leads onto the PCB.
Which results in a capacitance half that of each individual capacitor, i.e. 5 ĀµF in your example, so start with 22 ĀµF if you want to end up at (near) 10 ĀµF.
Youāre absolutely right there, thatās what happens when one writes at silly a.m. Two 20Ī¼F capacitors are needed, or two 22Ī¼F which are more common. I recently had to recap an old preamp that was full of those!
Hey! In your repository you only have the hex file for the mutated version, right? is that this very advanced bees-in-the-trees firmware? For using your modifications with the āstandardā firmware I would need to build the firmware using the source files in your repository?
I would pay good money for the correct blue pill thatās already programmed 
2 Likes
Iāve bought a few Blue Pills and used them in 2 Peaks and 1 Braids (and some experiments) without any problems. Programming them is easy. Iāve found that one out of 7 did not work properly although the MCU āacceptedā the firmware. It was not possible for me to tell which will and which wonāt, but in my experience, most will work. So Iād suggest you buy a few from different vendors and try your luck.
5 Likes
Iām honestly a bit confused how we ever got the right boards in the first place.
According to ST :
- the STM32F103C8x is 64k,
- the STM32F103CBx is 128k
- but the bluepill board was a 'C8 (64k) part
- and then there was a maple mini boards (and clones) that were CB (128k) but they have totally the wrong pinout. (and the original maple mini boards are also discontinued)
So it seems like the original THT Braids project was predicated on a bluepill clone boards that used the wrong (128k) microcontroller, but those are getting hard to find because ST now charges over $7 for the STM32F103CBx chip, so theyāre all using clones of the 'C8 chip.
Maybe itās time to just start looking at porting the Plaits to THT, since thatās based on an M4 chip instead of an M1, maybe we can get a few more years of development boards out of that.
5 Likes