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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