STM32F4 - Onboard DAC - Use as CV?

[Phatline]

is there any Driver-code out there - in the MidiboxWorld - to use the onboard Audio DAC for CV? (0-127)

i just need it for Velocity Control for the Accent of a TR606 which need a Voltage from ~4V to 15V (a little scale with an OP amp should do the trick hardwareside - i think)

In the past i have done Accent with a Shiftregister, 8 Varistors and a Transistor... worked well, but steppy.

 

thx phat

Edited June 1, 2016 by Phatline

[Psykhaze]

i re quote here =)
From Core32 Ucapps Page :

Quote

• Pin mapping suboptimal in some cases. E.g., the outputs of the integrated DAC (not the on-board Audio-DAC) overlay SPI1 pins. However, one DAC channel has been freed up with the small drawback that SPI1 can't be used in slave mode.
  The IO pins of the SDIO peripheral (high speed SD Card access) conflicts with the on-board Audio DAC, so that it can't be used.
  Although the chip contains 6 UARTs, only 4 RX and TX pins could be found for MIDI IN/OUT. IN3/OUT3 even have to use two different UARTs.

So using on board DAC will cause conflicts with SD/ Midi Interface. We can don't care about it , or using serial registers. It sounds better to me,moreover for this resolution =) 74HC595 & 74HC165 have a 8 bit-wide resolution, wich give you from 0 up to 254 value per adress, so twice more we need =)
if still steppy, we can use 2 registers adresses instead of one per parameter to increase definition : the trick is filtering/mixing signals to keep each register working with a half (high or low) range part of the signal.

If Amplitude scaling necessary to bring back the signals to the correct voltage , could be done trough a classic amplifying OpAmp setup (like mcp6004)

Hope it helped

Edited June 1, 2016 by Psykhaze