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Messages - Xavier

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PreenFM2 / Re: Feature request?
« on: May 16, 2017, 09:37:33 AM »

Nice to read you enjoy your preenfm2  :)
I never know how to answer to question that begins by "is it possible"....
Do you ask (1) if it's possible, (2) if it's easy to do, or (3) if i would plan to do it ?

1 - Yes it's possible, the firmware is open source.
The midi to audio conversion is done here :
So you have to modify the code to introduce a delay at this point. Requires a little research to do that.
Then the timers for each instrument must be added somewhere in the settings.
2 - Not very easy
3 - No. It will add some complexity in the menus and settings that is not worth it to my opinion.

Possible Alternative : for the instrument you want to introduce a delay
. Set all mix* params to 0.00
. Set a matrix row like this : env2 1.0 mix*
. Then select the modulation : "Free Env 2" like this : "<D> 0.00 5.0 No"
Where <D> is the delay before your sound will begin.

Pseudo delay effect : can be done by
. using one LFO to pan the sound in the matrix (lfo1 1.0 pan*)
. And the gate target matrix (with an other LFO twice faster) to make the sound hearable only when right or left.

PreenFM2 / Re: Output volume vs polyphony..
« on: May 16, 2017, 09:18:44 AM »

This is how it works.
The voice mixer is 100% digital.

So it maximizes the number of actual bits for each used voice.
Same thing : instrument not used should have their number of voice set to 0 so that it does not take any room in the digital mixer.

Summary : for best resolution, only set the number of voices you really need for each instrument.

PreenFM2 / Re: Can't save to usb
« on: May 15, 2017, 10:48:59 AM »
Thanks for the details (i've modified your subjet).
Sounds like a bug.
Don't know if it's easily fixable as the USB library is the one from STM (the MCU manufacturer).

PreenFM2 / Re: A higher polyphony ??
« on: May 15, 2017, 10:30:52 AM »

What you describe is of course possible, but it's a LOT of work.
No i won't work on that  ;)

You can chain 2 preenfm2. But they'll have to play different instrument.
Polyphony on one instrument cannot be expanded.


PreenFM2 / Re: Stm32F4Discovery port
« on: May 11, 2017, 03:45:36 PM »
Hi Xavier!

Thanks for the tip. I just checked the symbol list, and found, that at 08041AC0 there is the OTG_FS IRQ handler, and thought that the 0x28041AC0 dumped PC value can be the same with a memory mapping offset. I'll try to find it with gdb, though I only used it before to debug a connected target.

Yes RAM adress in the STM32F4 is 0x20000000. So this is the same adress moved into MCU RAM !

PreenFM2 / Re: Harsh noise at 13,5kHz from preenFM2
« on: May 11, 2017, 03:40:37 PM »

Yes this come from the yellow OLED display.
Verify your PCB version and read carefully this :


PreenFM2 / Re: Stm32F4Discovery port
« on: May 11, 2017, 09:38:27 AM »
The goal of this register dump is to be able to find where the firmware crashed.
I'm away from my dev computer and I don't remember exacly the steps to debug.
The PC (program counter) value is where it crashed.

With a mix of gdb, elf binary, 'layout split' or asm, and a gdb function to go to the PC value, you should get the C++ line where it crashed.

PreenFM2 / Re: New slippers -> no USB
« on: May 09, 2017, 02:20:58 PM »
Cool  :)
Thanks for the update...

PreenFM2 / Re: Simulating Karplus Strong with PreenFM2
« on: May 08, 2017, 05:27:48 PM »

Thanks a lot to take the time to share what you've found  :D

PreenFM2 / Re: Can't save to usb
« on: May 08, 2017, 05:17:31 PM »
Could you describe with more details what you're exactly doing ?

PreenFM2 / Re: Connecting..
« on: May 04, 2017, 10:53:47 PM »

First verify you have JMP1 shorted. But if the 7805 is hot i assume it's OK.

I verified and saw you have a kit with a LCD display.
Is the LCD brighter when you switch on the preenfm ?
Have you tried to turn the contrast pot ?

Then check the different voltage as shown in the message #6 of this thread :


PreenFM2 / Re: Connecting..
« on: May 03, 2017, 09:22:28 PM »

9V, + at the center, should work.
That's strange.
Check that your power supply does not provide more than that.
The 7805 is hot, but that should not be a problem.
Reverse polarity should be blocked by the diode D2.

But smoke is a problem ! Maybe a cap in the wrong polarity ?

Midi polarity is important and is explained here :

PreenFM2 / Re: New slippers -> no USB
« on: May 03, 2017, 05:28:13 PM »
Did you check the external USB solder joins on the main PCB ?

You can order a preenF405 from the shop.
It should be compatible with your white PCB (check it's a R5 version) and you won't need a internal USB cable.
I'll get it back and reimbourse you if that does not fix anything.

PreenFM2 / Re: New PreenFM2 user, old PreenFM2
« on: May 03, 2017, 05:23:41 PM »

Have you tried with a standalone USB power supply such as one for tablet/smartphone ?
Or with a 9V power supply ?

You can plug directly a headset to one of the audio output to check the sound quality.

PreenFM2 / Re: New slippers -> no USB
« on: May 02, 2017, 11:59:58 AM »
OK it's a CERB40.
Seems like there's a problem with the internal mini USB cable....

Can you post a picture of your PCB + CERB40 inserted ?

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