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Topics - zelea2

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PreenFM2 / VolcaFM as development platform for PreenFM
« on: January 16, 2018, 08:48:33 AM »
I am in the process of adding note velocity on my VolcaFM and while I was reversing the schematics I couldn't stop noticing similarities with a PreenFM2.
MIDI Keys Velocity for Korg VolcaFM

Both devices use an ARM Cortex-M4 so the PreenFM2 firmware could be ported (in theory) to a VolcaFM. Of course the original code will be lost
forever. The Volca uses a companion processor to read the touch keys and the protocol could be quickly reversed by hooking a logic analyzer on the SPI connector. The Volca doesn't have a nice screen, only a 9x7-segment display and neither it has the USB connectivity or pen drive interface. Instead is has a stereo 24-bit DAC.

What do you think; is it worth the effort to port this firmware to a Volca?
The Volca's firmware can be updated via an audio file played from the computer. I'll have a look in the future to see if that can be reversed so we could save the original firmware. Or maybe they've forgotten to fuse protect their Spansion FM4 processor.

PreenFM2 / PreenFM2 SMD version
« on: October 31, 2017, 07:23:02 PM »
I'm in the process of redesigning a SMD version of PreenFM2.
The original goal of this design was probably to make it as easy as possible for people to solder their own kit.
Unfortunately  the Cerb40 module cannot be bought anymore so someone else has to solder the LQFP64.

I plan to build 5 pieces of this new design and make it as cheap as possible. The majority of components
will be bought from Aliexpress and the rest from Farnell.
- there will be just one PCB (15x10cm), no sockets.
- the 2 shift registers replaced with MCP23S17 (port expander)
- the 2 DACs replaced with PCM5102A
- OpAmp replaced with OPA2337
- extra MiniUSB socket placed on the main board
- all resistors and caps as SMD 0603
- cheap LCD 40x4 (no OLED)
I believe the total BOM will be well below 100$ (without the case)
The changes to the firmware to accomodate the new DAC and SPI-expander will be trivial and made with #ifdefs

Since I'm not comfortable with this KiCAD tool I have switched to OrCAD+Specctra and I'll make all design files available.
So far I've been able to export the PCB as GenCAD and after a lot of massaging I've now got an OrCAD PCB of the current
design with SMD passives. This way all the sizes and encoders/switches position will be preserved and I'll be able to use
the same cases.

PreenFM2 / Schematics library
« on: October 28, 2017, 01:34:51 AM »
Hi Xavier,

Would you mind checking the missing "special" Kicad library in git? The schematics looks broken and with missing symbols when I try to load it in Kicad.


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