PreenFM > preenfm2 and preenfm3

PCB Only/BOM problem reports

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1. You forgot to mention the 330nF capacitor in the bom. Now I need to make a new order for it :/ Or can I use something else?
2. I ordered the encoder alternative PEC11R. Unfortunatly it has 2 pins to much (on the other side). Should I cut them?
3. The mini usb connector (female) looks different. How should I solder?

Thanks :)

1. Sorry.. Just added.
I'll leave the text at the top of the BOM page one more week  ;)
This 330nF capacitor is used to filter the input 7-9V DC in before the 5V (7805) regulator.
It's not essential at all. Should work without. Can be replaced by anything bigger.
In the worst case put a 100nF here.

2. Yes, the alternative encoder has a switch. And the 2 aditionnal pins are the pins for this switch. You can cut them.

3. Contact 2 and 3 (the one that needs to be plug to the PreenFM PCB) shows up clearly in this PDF :
I think you can plug the black part directly in the CERB40 board. Metal parts will make things thicker.


Okay, I finished everything. I still didn't got my display, but it should work without display, right?
Unfortunately I can't get it to work :/ Jumper 1 and 2 are closed.

I uploaded the bootloader and firmware to the cerb40, which worked great (I set a jumper to jump3 and connected a usb cable directly to the mini usb connector of cerb).

(btw. I didn't add any capacitor on the 330nf place)

Now nothing works (except puting it again to dfu).
- If I connect an usb cable directly to the cerb I can't see any device on my computer (if cerb isn't in dfu mode)
- If i connect a 9v 1a to it, nothing happens. I tried so send midi notes to it via the din5 connector, but it isn't working.
- The only thing I can see is my blinking usb storage stick if I connect it to the usb connection.

Any idea why? :/

Oh and for what is the usb connection (not the host one for usb storage)? Only for usb midi or also for powering it without power cable? If also for powering, it isn't working either. :/

Without display it's of course hard to see, if it's running. Should the led blink if it's receive midi notes? And how can I activate usb midi blind without display?

Yes the USB midi also power the PreenFM.
The Led is currently not used.

Initial test:
. Do the led of the LCD turn on when the PreenFM is power up ?
. Display : have you tried to turn the LCD contrast resistor to the 2 extreme position ?
. Did you remove jm3 after having flashed the firmware ? jmp3 force the PreenFM2 to boot in DFU mode.
. Double check the command you used to flash the bootloader and firmware and do it again. Did you run the command from the zip file ?

To check if the bootlader is correctly flashed.
. see . Open Jmp3.  power up the PreenFM while pressing button 3. You should see the device on your computer exactly as if Jm3 is closed.

To Activate USB midi without display, download the attached "settings.pfm" and copy it on your USB stick in "/pfm2/" folder.
But you should hear sound when sending notes to Din5 input any way.

Let me know how it goes,
If no progress, i'll upload a picture to check the ground, 3.3V and 5V on the PCB.


Sorry for the false alarm, everything is working fine.

Because I still don't have the lcd display, i was confused, if it's working. However USB midi showed me the device on my mac and I could play notes :) Awesome synth.

A suggestion:
Replace the two headers for usb connection with a female usb a connector. I found the process of soldering the cable a bit hard. I destroyed the mouser mini male connector, because the pins were too close each other and I melted the plastic. 0.3m mini usb cables are everywhere available and it would allow to just connect the cable without soldering.


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