XMOS-based Asynchronous USB to I2S interface

[wlowes]

Does anyone have experience with powering WaveIO with an exernal power supply?
I presume one only has to move the jumper to EXT, and attach a supply with sufficient power. Does the LED light up when sufficient power is attached?

I have played around, but did not have sufficient power to get to 5v, and the LED did not light.

What are your impressions of the sound quality difference with external power?

[shoom]

Hi wlowes

i'm using a simple LT1086 reg feeding JLH ripple eater which seems to work pretty well in my set up.

to my ears avoiding the PC +5V Vbus and using a nice linear supply improved the sound a little.

still realy enjoying the board Lorien

take care

[reo]

Originally Posted by wlowes

Does anyone have experience with powering WaveIO with an exernal power supply?
I presume one only has to move the jumper to EXT, and attach a supply with sufficient power. Does the LED light up when sufficient power is attached?

I have played around, but did not have sufficient power to get to 5v, and the LED did not light.

What are your impressions of the sound quality difference with external power?

i am using a Placid HD regulator and the appropriate toroid power supply at 5V@460mA to power WaveI/O .
Yes the LED should light up , but does it need 5V to turn on, i don't know, also i don't know if USB1 gives out enough mA to power the light and the WaveI/O, but USB2 does give out 460mA, providing that you have USB2 from your source.

[rsdio]

Originally Posted by reo

i don't know if USB1 gives out enough mA to power the light and the WaveI/O, but USB2 does give out 460mA, providing that you have USB2 from your source.

USB 1 and USB 2 have identical power specifications. Both provide nominal 5 V, starting at a minimum of 100 mA for all Devices, then as much as 500 mA if the Configuration is successfully negotiated with the USB Host. According to the USB specifications, no more than 500 mA must be provided, although some chargers will exceed that power level if certain conditions are met.

Meanwhile, 460 mA does not appear anywhere in the USB specifications, neither USB1 nor USB2. The only time that value might appear is when a specific USB Device requests 460 mA by placing the value of 230 in the Configuration Descriptor.

[reo]

i have wondered what comes out of my so called usb2 header controler, so i measured the output with a multimeter and it produced closer to a steady 480 +,-, mA , but i did not try the usb1 header so i can't say . And i can not answer in reference to wlowes question pertaining to if sound quality changes when using either usb2 or ext. power since they are both adjusted to equal mA.

[rsdio]

Originally Posted by reo

i have wondered what comes out of my so called usb2 header controler, so i measured the output with a multimeter and it produced closer to a steady 480 +,-, mA , but i did not try the usb1 header so i can't say . And i can not answer in reference to wlowes question pertaining to if sound quality changes when using either usb2 or ext. power since they are both adjusted to equal mA.

An important law of physics is that V=IR, or I=V/R. In other words, for any circuit that controls the voltage with a regulator, you cannot predict the current for all possible attached devices unless you also know the impedance of those devices. You can't just plug in one multimeter and expect to know anything definitive about the current, especially not when you change the Device.

It is possible to limit the maximum current using special protection circuits, but it's not really possible to force more current than the V=IR equation. Thus, with a really high impedance, the current will be much lower than 500 mA.

In your case, perhaps you had a 10.4167 Ω impedance, assuming the port was holding a perfect 5.000 V. Otherwise, there could be any number of reasons why you measured 480 mA. The truth is that if you could measure the current with several different USB Devices attached, then you would see a different current for each Device.

p.s. Just because you adjust an external power source to 480 mA does not mean that it will produce the same audio quality as a USB Host port that provides 480 mA. There are many, many more variables involved than the nominal current consumption.

[wlowes]

Thanks all for the feed back. I realize one layer of error I made. I was setting the wrong jumper (USB). With the correct jumper set to EXT and 4.9 volts of power, I get a steady light on the LED, but the PC will not recognize the WaveIO board. I go back to power from the USB, and it springs to life. I tried a different copy of the OS and installed drivers from scratch, but the card was not seen and driver install was stalled.

Any ideas what I am doing wrong? I just want to minimize the power load in the PC and to supply clean power to WaveIO.
thanks,
Walter

[reo]

I don't think the driver differentiates or couldn't care less what you power your WaveI/O with., unless maybe if you you don't have enough mA. from your external power supply ?. try to bring it up above 450mA. but keep it under 500mA., which is what your usb2 bus from the pc normally delivers.

[hochopeper]

You can't really set the current the device will draw what it needs.

wlowes, have you checked the voltage once the device is drawing current or only on an open circuit? What is the external supply you're trying to use?

[Lorien]

External power supply

--------------------------------------------------------------------------------
Thanks all for the feed back. I realize one layer of error I made. I was setting the wrong jumper (USB). With the correct jumper set to EXT and 4.9 volts of power, I get a steady light on the LED, but the PC will not recognize the WaveIO board. I go back to power from the USB, and it springs to life. I tried a different copy of the OS and installed drivers from scratch, but the card was not seen and driver install was stalled.

Any ideas what I am doing wrong? I just want to minimize the power load in the PC and to supply clean power to WaveIO.
thanks,
Walter

Hello Walter,
make sure that J8 jumper is set on the BRD side all the time! That jumper is used only to switch between on-board (BRD) USB-B connector and EXTernal USB signals available on J1 pin-header for cables like the one in the attached image. In your case, J12 must be placed on EXT option to be able to power up WaveIO using external sources.
Hope it helps,
L