#28

the aleph uses the AD1939 codec in standalone mode. by default it runs at 48k, but it can be hacked to run at other sampling rates up to 192k. i believe this can be achieved just by setting the ADC control register (p.27 of linked datasheet.)

1 Like
#29

@rick , stm32Cube is awful, you probably want just their ā€œstandard peripheral libraryā€ if there is one for the part youā€™re using.

have also had some success with ChibiOS HAL layer.

#30

handed this off to the most hardcore embedded guru in our office - he couldnā€™t make it go! This guy was debugging on the level of checking registers / pins against microprocessor manual & board schematic, way deeper than Iā€™d have been able to go.

Definitely wouldnā€™t reccomend the nucleo-STM32F746 board to any weekend warriors hoping to quickly get the i2s ports up & running. If anyone has a working recipe for that boardā€™s i2s peripherals, donā€™t be shy about sharing! Kind of a shame since those nucleo boards are cheap as chips, but I guess maybe the atmel M7 offerings may be a better choice for nowā€¦

Oh and by the way I took the plunge and hacked on a linux kernel module to provide a ā€˜codec-lessā€™ i2s driver for the raspberry pi 3. It works pretty good! Just trying to also get the RT-patched kernel cooking on that platform - should be able to distribute an image of my arch setup for anyone trying to get a quick 'n dirty i2s floating-point DSP host on the go with < $100 worth of bitsā€¦

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#31

iā€™d love to get an image or pkgbuild for that moduleā€¦ got a couple rpi3ā€™s here that are earmarked for supercollider experiment, and running arch would be ideal.

2 Likes
#32

tomorrow night I will try and get the RT pi3/arch setup packed up to share, also some rough notes on how the system is set up before I forget everything. Had, wanted to fix the remaining bugs there before distributing an image, but maybe if I just upload it warts and all, others may also be able to help out with those. Itā€™s only an annoying delay on ssh login, also the latency can probably be tuned down further using IRQ fettling - got things down around a couple of milliseconds, and not yet seeing quite the ultra-stable performance under heavy DSP load I anticipated.

Testbench for these initial results is a usbstreamer usb->i2s device and rpi3 running as i2s slave - maybe stability would be improved if the pi3 works as i2s master. On the slightly crazy side, should totally be possible to squeeze a multichannel setup in there using multiple DAC/ADCs with icestick fpga to interleave/deinterleave, but this would require going quite a bit deeper into the kernel module work or hacking on jackā€¦

#33

Wow, I did not know the Axoloti. Itā€™s cheap and seems really cool, does someone here use it ? Been looking for that kind of stuff for months.

#34

Yup Im a big fan of it, use it daily ā€¦ its a lot of fun, and really flexible.
theres a lines post here about it.

if you want to learn more go to the axoloti forum its a vibrant and friendly communityā€¦ and if you have any questions (e.g. about suitability) youā€™ll get the answers there :slight_smile:

#35

Oh, I realize I just watched your videos this morning on their forum, couldnā€™t remember when I saw you, now I know :wink:

Iā€™ll buy it this week. :smiley:

1 Like
#36

For the F7 they only released a HAL library. It seems theyā€™ve made a lot of improvements since I last tried to use it and the code generator from CubeMX is not bad at getting stuff running quickly to test the board. Still will probably ultimately replace most of the generated codeā€¦

#37

afaik noone has demonstrated a working i2s echo program or similar using the marked i2s pins on nucleo F7 boards. Kind of a deal-breaker if you want to roll your own ā€˜reconfigurable sound synthesis HWā€™!

Actually someone from ST finally got back to me on the i2s question - apparently you have to buy two boards in order to satisfy their tech support that i2s master isnā€™t coming to life (90% sure the relevant pins are unresponsive when flashing i2s master program & in fact the ISR to send data is never called in their example code):
https://my.st.com/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/Flat.aspx?RootFolder=https%3A%2F%2Fmy.st.com%2Fpublic%2FSTe2ecommunities%2Fmcu%2FLists%2Fcortex_mx_stm32%2Fnucleo-F746ZG%20I2S%20example&FolderCTID=0x01200200770978C69A1141439FE559EB459D7580009C4E14902C3CDE46A77F0FFD06506F5B&currentviews=32
Would be so awesome to see this issue actually get solved - cortex M7 is quite the alluring beast but rapidly got out of my depth on this oneā€¦

#38

Iā€™m working on getting I2S working right nowā€¦ will let you know :wink:

2 Likes
#39

Might never get round to cleaning up the whole arch system & config for others to use, but here are the bare i2s kernel modules at least!

https://github.com/rick-monster/bare-i2s-pi3

think I tested this guyā€™s pre-compiled RT kernel on arch and it works:

http://www.frank-durr.de/?p=203

Also successfully compiled my own by following his instructions. Hereā€™s the pi kernel with RT patch already applied:
https://github.com/rick-monster/linux

Youā€™ll probably find systemd borks a bit with either frank-durr or custom-compiled kernel. In particular systemd-logind wonā€™t run on startup so ssh logins hang for 20s after password before finally giving up and working. Havenā€™t found a fix for that, but I think it may help to recompile systemd from github HEADā€¦

#40

Hey - curious, did you have any success with the nucleo F7 i2s peripherals?

#41

Yes. It was actually not very hard to set up. It turned out the problem was another fault on the board and not a problem with my programming :slight_smile:

Iā€™m actually using the SAI, which can also speak I2S, but the configuration is similar.

1 Like
#42

Anyway, the easiest way to get everything set up is to use their CubeMX software to generate the code. Most of the work is in setting up the clocking. You need to ensure the peripheral is sending the right master clock, frame clock, and serial clock to your I2S device. That all depends on settings the right PLL multipliers and dividers for the clock rate at which your processor is being run at. It can be a bit tricky to figure out manually, which is why the clock configuration screen in CubeMX is very handy.

1 Like
#43

Hereā€™s another teensy based framework, called Prynth:

2 Likes
#44

its an interesting one, seems to be mainly a small hardware board that has multiplexed analog i/o, so you can have up to 80 analog inputsā€¦ quite nice, as Id assume this could be used with other platforms.
the rest seems fairly ā€˜standardā€™, RPi, supercollider, USB audio interfaceā€¦
I might give this a go, since Iā€™ve got a spare PI2 with a hifiberry fitted (rather than a usb audio interface).
the only ā€˜caveatā€™ I have isā€¦ latency, it doesnā€™t appear to be using realtime OS as far as i can tellā€¦ though of course they could switch this out.

will be a nice project though, if others start sharing project details they create.
(I was a little disappointed they didnā€™t have the schematic/code for the MITT :slight_smile: )

2 Likes
#45

hey
hope you donā€™t mind but i added norns and tried to make the chart a bit more legible

2 Likes
#46

perhaps its should say the Norns CPU is the ARM Cortex A53 (same as the rPI3/PiSound)
for those not knowing what the compute module 3 is.

1 Like
#47

great suggestion

done!