XMOS-based Asynchronous USB to I2S interface

[suffolk tony]

An observation; I found that when I tried to use an HD Placid to power my Wave IO board it wouldn't produce enough power in its standard form & I had to resort to a 317-based supply before moving up to a Paul Hynes regulator, which sounded appreciably better.

[lindamar]

You are very right Suffolk, I modified the Placid just a bit in order to produce more juice and less pulp (in twispear-terminology ) ... seriously, I re-touched it to provide 750 miliamps and that is more thank enough to power de WaveIO in my humble opinion.

cheers
Pepe

[rsdio]

Originally Posted by Lorien

perhaps it's related to USB descriptors that WaveIO is reporting due enumeration process. Even if I didn't dig too much into XMOS firmware, I remember seeing somewhere that there was one value (or more?) that is/are telling to host the amount of current needed for the device plugged into USB port to function properly. Being a hungry one, WaveIO reports 500mA which I suppose it's too much for iPad (a battery powered device) to give it a shot.
Anyway, thank you for telling me! I'll look into the firmware and on next revision I'll set descriptos accordingly!

Edit: I know that it's too early (given the fact that you received your WaveIO recently) but if I'll find those values and make the changes accordingly, you could send card back to rewrite the firmware hoping that you can use WaveIO with iPad too. Anyway, if those values will be changed, there's no going back to power WaveIO through USB Bus because less than 500mA is a no go for it

The USB Specifications say that a device that can work with both self-power and bus-power should change descriptors accordingly. Such a device needs an input pin on the processor that can detect the source of power. For example, if external power is detected, the Descriptors should indicate self-power, but if external power is missing then the Descriptors should indicate bus-power.

You should also measure the actual current used under bus power and report that instead of just using the maximum of 500 mA, although I suppose that could be difficult to measure if some people are using bus power for the DAC, since that would be unknown because it is different for every chip.

There is no reason to say "there's no going back," because this sort of problem has been solved with many USB Devices.

[ed linssen]

Originally Posted by lindamar

You are very right Suffolk, I modified the Placid just a bit in order to produce more juice and less pulp (in twispear-terminology ) ... seriously, I re-touched it to provide 750 miliamps and that is more thank enough to power de WaveIO in my humble opinion.

cheers
Pepe

Hi Pepe,

Could you share your changes to the standard Placid HD to get the 750mA?
Thanks in advance,
Ed

[Lorien]

@rsdio: I was thinking for future revisions to reserve a pin to change USB descriptors accordingly but in lindamar's case I do want to preserve its WaveIO PCB in actual form (without cutting traces/adding wires or changing the layout in any other possible way) since I hate to do this kind of jobs. What I said before was meant only in lindamar's case (knowing that he is already using external PSU). Anyway, thank you for your help... now I know that what I was thinking off before is confirmed!
Kind regards,
L

[rsdio]

Originally Posted by Lorien

@rsdio: I was thinking for future revisions to reserve a pin to change USB descriptors accordingly but in lindamar's case I do want to preserve its WaveIO PCB in actual form (without cutting traces/adding wires or changing the layout in any other possible way) since I hate to do this kind of jobs. What I said before was meant only in lindamar's case (knowing that he is already using external PSU). Anyway, thank you for your help... now I know that what I was thinking off before is confirmed!

Ah, yes, existing boards might be difficult to fix.

As for future revisions, you have at least three options:

1) Detect USB power, using diodes to protect against external power reaching the I/O pin. Then, if USB power is missing, but the processor is running, then there must be external power, so the Descriptor should indicate self power.

2) Detect External power, again using diodes to protect again USB power reaching that I/O pin. If external power is missing, then report Descriptors showing bus power with the appropriate current.

3) Just have a simple I/O pin with a logic input, set by something as simple as jumpers. This allows for user error, but it would be fairly easy to have a pair of jumpers to select power source and Descriptor variation.

Note that many of the Application Notes for USB processors have example circuits for the self-power versus bus-power detection.

[JamesHill]

Hi Lucian,

Board arrived last week, it is a fantastic piece of engineering and works very well. Thanks for your work on an excellent value product.

Originally Posted by gioz

Hi,
Wave I0 + Alix 3d2 + voyage mpd + 24/192 files
Is it a good idea?? Work well?

Yes it does, sounding excellent with my Buffalo 2 DAC at 24/192 Khz.

Just waiting for the FIFO GB 2 to finish my setup now!

Best Regards,

James.

[analog_sa]

Today i tried hooking the WaveIO to my old 1794 dac. The dac had an AD1896 asrc in front so initially the WaveIO I2S output was connected to the asrc. Worked fine. Removed the 1896 and connected the I2S signal straight to the 1794 and this time also used the WaveIO master clock output. All was fine @24.576 MHz but at sample rates based on 22.5792 MHz there was only noise and distortion. The 1794 is supposed to autodetect the master clock frequency but something isn't working. Am i doing something wrong? Even went as far as checking if the WaveIO is indeed changing the MCLK frequency . It is.
Any ideas?

[pinnocchio]

A little help please..

Hi Lucian, please disregard my PM...

I had totally forgotten to power the isolator with a 3.3V source for the I2S output...

Now I have another problem and maybe someone can shed some light...

I'm getting sound but with extremely high scratching noise when and only when music is playing. At first I thought the USB port might not have been supplying enough current so I plugged in a regulator. Checked the voltage and it was not dropping. 5.08V steady... 3.3V on isolator is also fed by another reg which has its ground connected to the isolated ground and the +V pin.

Could the USB cable length be an issue? If yes, What is the maximum length?

I'm also using JRiver 17 with WASAPI, WASAPI event style and ASIO and they all do the same thing.

Anything you can suggest I test?

Thanks
Do

[ENSen]

I had problems with a 5m usb cable, then switched to a 2m one and it worked fine.

Originally Posted by pinnocchio

A little help please..

Hi Lucian, please disregard my PM...

I had totally forgotten to power the isolator with a 3.3V source for the I2S output...

Now I have another problem and maybe someone can shed some light...

I'm getting sound but with extremely high scratching noise when and only when music is playing. At first I thought the USB port might not have been supplying enough current so I plugged in a regulator. Checked the voltage and it was not dropping. 5.08V steady... 3.3V on isolator is also fed by another reg which has its ground connected to the isolated ground and the +V pin.

Could the USB cable length be an issue? If yes, What is the maximum length?

I'm also using JRiver 17 with WASAPI, WASAPI event style and ASIO and they all do the same thing.

Anything you can suggest I test?

Thanks
Do