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 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-Sche...
or
http://www.raspberrypi.org/documentation/hardware/raspberrypi/Raspberry-Pi-R...
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...
here is a photo with the new layout and new USB chip:
http://www.raspberrypi.org/wp-content/uploads/2014/07/rsz_b-.jpg
Simon