PO-12 Pattern Reset?

Hi all !!!

I’m using my PO-12 with my modular and slaving the PO-12 to Mutable Instruments Yarns module. Works super good but can I reset the pattern with any external gate?
I have seen http://hackingthepo.weebly.com for hacking my PO-12 but don’t know where to start. Any DIY pro’s that can help me?


By “reseting the pattern” you mean toggling the Play button?

If yes, in the POTS & KEYS section there is a picture of the button pinout. You need to generate two pulse transitions from 3V to 0V at the Play button input. Not sure how fast the PO debounces and responds to key presses, so you would need to experimento with the pulse widths. I’m assuming you want to use a modular CV pulse as a trigger, so you need to be careful with the voltage conversions, since the PO MCU is not tolerante to voltage levels higher than the its own power supply. I’m more into SW, so don’t know which is the best HW way to achieve that.

By the way, I created that hackingthepo site! :slight_smile:

So if I solder the positive pin on the reset pad ( 2nd pad bottom row) and the negative pin on the ground pad (1st pad bottom row) it should work? I would still need my Yarns to send two quick triggers to reset a pattern right? I would use a female mono jack… Great PO hacks ressources on your site btw!

Applying a pulse to the RESET pad you refer to will force the PO to restart, as if turned off and on. If you just want to force the sequencer back to step 1 then you prabably should use the Play button input pin, as I mentioned before. Anyway, both are triggered by a logic level low, so you need Yarns to generate an inverse pulse, i.e., a normaly high level output that pulses to 0V. Does it support that?

Also, make sure you add a reverse polarized 1N4148 or similar diode to the positive Yarns output, so that no voltage flows while the pulse is idle and only the 0V pulse gets thru. I think Yarns output at 5V, not 3V required by the PO, so that should keep things safe even with the voltage level difference.

Yes go back to step one

Yarns outputs 5v p to p gates

As per the Yarns manual, “Gates are +5V, positive polarity (ON = +5V)”, so it will not work unless you add some extra circuit in there to reverse the pulse, i.e., ON = 0V.

Is it conplicated to do?

I tried this solution based on a single NPN transistor working as an open collector inverter and it seems to work. You will need the following:

- 1 transistor 2N3904
- 1 resistor 10K, 1/8W or lower

Solder both transistor leads to the Play button pins as shown in the picture below. Make sure the flat side of the transistor is facing towards the display. The transistor middle pin should be connected to a resistor lead. The other resistor lead should go to the positive Yarns gate output (green wire). The negative Yarns gate output should go to a PO ground pad in the back (GND). The button or pot metal chassis is also a good ground point.

Note that you may use additional transistors attached to other pins and drive them all using your modular!

Please let me know if you need more details.

Wow thanks!!

I still need to send two triggers with that setup right?

I’d love to hear this when you are done!

Each trigger will count as a key press. So, if the sequencer is running, the first trigger will stop it and the second will restart it from step one.

Now, if you connect transistors to keys 1-16, you could independently control each one, e.g., send a single (longer) pulse to play just that sound while the sequencer is stopped!


Is there a video which shows this hack working?