[PD] Jonathan Wilkes via Pd-list <pd-list at lists.iem.at>

[Jonathan Wilkes via Pd-list]

On 07/16/2014 11:36 PM, Simon Wise via Pd-list wrote:
> On 16/07/14 00:15, Dan Wilcox via Pd-list wrote:
>> The onbopard audio might be better, but from what I could tell by the 
>> press
>> release, it does't add a dedicated USB controller. In that case, it will
>> probably still have the same issues with USB audio devices.
>>
>>> Anybody played with the new Raspberry Pi model?  It claims to 
>>> haveimproved
>> audio; I'm curious how that would effect a running instance of Pd on 
>> the Pi.
>
> Haven't got mine delivered yet (it is on the way) but looking at the 
> (minimal) schematics provided so far they have improved the power .. 
> the miniUSB has gone up from 1.1 amps to 2 amps with a regulator 
> added. Also the whole is said to draw significantly less power 
> (why???) .. so other things have changed also. The USB/Ethernet hub 
> has been changed to the 4-out version of the same chip, maybe this 
> version is also better in other ways? I don't know if this hub is the 
> problem for usb, or if the problem is the usb out of the main chip ... 
> if the model A (without this hub) does better with usb audio cards 
> than model B then the problem is here, but I have not got a model A to 
> test with.
>
> The board layout is completely new, so it might also be cleaner for 
> audio? I will test noise and latency when it gets here.

I ordered one the other day, so I'll definitely test it, too.  (I've 
never played with an RPI before, so I'll probably doing some general 
playing around before getting to Pd specifically.)

>
> I have just received 2 wolfson audio cards, which use the digital PCM 
> link (rather than usb) and also expose another PCM link on a header 
> plus a clock input (to the Pi header). They are quite flexible as far 
> as clocking goes so several Pis could run these and share a single 
> clock source (and pass digital audio between them), so I'll be testing 
> that. It mounts onto the B-rev2 using the digital PCM on the 8 holes 
> near the main 26 pin breakout. The B+ adds more GPIOs to a 40 pin 
> breakout instead which include this stereo PCM link (and several 
> others ... the clock, PWM and most of the digital interfaces can now 
> be used simultaneously) but the digital audio is on different GPIOs so 
> there will need to be some patching and some leads made up to use it 
> on the B+. Unfortunately the wolfson card does not bring out the 
> balanced audio pins from the chip (it has multiple DAC/ADCs) but 
> instead it connects built in stereo mics, 2W amplified outputs and such.
>
> The B rev2 schematics with the old power in and showing the low pass 
> filter circuit on the PWM outputs providing the analogue audio:
>
> http://www.raspberrypi.org/wp-content/uploads/2012/10/Raspberry-Pi-R2.0-Schematics-Issue2.2_027.pdf 
>
>
> or
>
> http://www.raspberrypi.org/documentation/hardware/raspberrypi/Raspberry-Pi-Rev-2.1-Model-AB-Schematics.pdf 
>
>
> power is top of page 1, audio is lower right of page 2.
>
> the new schematics with new power etc, with no mention of changes to 
> the audio filter circuit (just the changes to the audio jack):
>
> http://www.raspberrypi.org/documentation/hardware/raspberrypi/Raspberry-Pi-B-Plus-V1.2-Schematics.pdf 
>
>
> here is a photo with the new layout and new USB chip:
>
> http://www.raspberrypi.org/wp-content/uploads/2014/07/rsz_b-.jpg

This is all very exciting!

-Jonathan

>
>
> Simon
>
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