Mike, what F4 chip are you using?
A dual DAC I drive uses a I2S port. It is driven via interrupt triggered DMA.
The bit rate/clock is approx 1.4Mhz for 44.1Khz stereo sample rate.
That DMA works great but it doesn't leave much time between interrupts to do other things.. especially if they are slow processes.
Sounds like you ordered a lot of boards.. Kinda has you locked in for the design?
/Blaine
On Jan 30, 2019 8:44 AM, "support support@... [korgpolyex]" <korgpolyex@yahoogroups.com> wrote:
Hi Blaine,See the picture. This is the CPU replacement for the Poly-800. I just ordered 100 pieces to begin testing the hardware and writing new software.The board is based on the STM32F4. Poly-800 owners will have to remove the 80C85 CPU and pop this unit in.With this installed, there is enormous potential to give the Poly new voices. Much like you said below. We could place new voices before, after or in parallel with the Korg filter.Clearly, you have done a large amount of the work. And I don't believe in reinventing the wheel. So I would hope that we could come up with some way to integrate our activities in some way.For one thing, I would like to see if it is feasible to drive a dual D2A via my board. If that is possible, then I could probably reuse most of your code.On Tue, 2019-01-29 at 17:51 -0600, Synthetech bperkins211@... [korgpolyex] wrote:Hi Mike,I would be interested in collaborating with you. Did you have anything in mind or any details?I am still ironing things out with this.. but I believe in another month or so it will be working much more smoothly.It's slow going. I only have some evenings and weekends to dive into the coding. I've been learning alot along the way.It's taken a long time just to study the code to understand it enough to dive in and modify it the way I want it to work.Every night I mess around with it, it gets a bit better :).Honestly I didnt think I'd ever get it working, but I just kept at it and very surprised at the results.It could be possible to use a smaller chip, the F405RG instead of a 407. Get pin size down to 64 instead of 100.The possibilities can be very interesting. This synth could be mixed in with the Poly's original DCO's and perhaps have a way to selectively run it through the Analog Filter chip.Of course the built in FX wont be much good if you used them while running it thru the Poly's VCF.It's also very possible to make a standalone version too.. Could be a side project that people would be interested in.. a cheaper Shruthi.I just got in the $1.08 16/24bit stereo DACs from DigiKey. I'll have to wait a few weeks for some breakout boards I bought on ChinaEbay to mount/test them.Unbelievably cheap how much this stuff is now.I have a ton of ideas, very interested in hearing yours./BlaineOn Mon, Jan 28, 2019 at 6:09 PM support support@... [korgpolyex] <korgpolyex@yahoogroups.com> wrote:
Hi Blaine,it's great work! I am in the process of testing a new board for the Poly-800 that is based on an STM32F4 too! The design doesn't give the Poly any new DCO waveforms so I am very interested in your work and how we could collaborate. I would imagine it would be great to take what you have done and develop it into a board to go into the Poly.Let me know what you think about that./MikeOn Sun, 2019-01-27 at 20:57 -0600, Synthetech bperkins211@... [korgpolyex] wrote:Hey Mike,I noticed it's been awful quiet on the yahoogroups. Been busy?I've been working on and off on this STM32F4 synth chip.It's been a slow progress, but I think I may have something almost usable here.Here is a private/unlisted video..I'm keeping this quiet for now because I'm not sure if I want to share the work I've done so far with the public.Anyway, take a look and let me know what you think./Blaine