ODAC offerings from Various Vendors

[SY]

Are schematics and layouts publicly available for this device? If so, where do I find them? If not, this is one of several promotional threads for a commercial item, and the threads will be merged and put into the Vendors forum.

[GeorgeBoudreau]

You can find the reference schematics on the XMOS page.

I am planning to create, if possible, a XMOS based DIY USB-I2S engine similiar to the Atmel based audio-widget. This will be a base module for an open-source ODAC.

All of this is dependant on XMOS policy regarding their usb library.

George

[SY]

Originally Posted by GeorgeBoudreau

You can find the reference schematics on the XMOS page.

By "reference schematic," do you mean the actual full schematic of the device being sold here?

[fitzfish]

Originally Posted by qusp

yeah I dont get it, why use a 12Mhz clock when the majority of users will be playing 44.1khz material

A reference clock is necessary at any USB target device for internal circuitry that recovers the clock from the USB host interface data (desktop, laptop, etc). This reference clock is also often used as the reference clock for an internal PLL that generates the audio master clock for its Audio interfaces.

It appears that the 9023 clock is driven from the pin 3 output on the 7022 in this case

Cheers,
Dave

[GeorgeBoudreau]

Originally Posted by SY

By "reference schematic," do you mean the actual full schematic of the device being sold here?

The reference schematic refers to the XMOS evaluation board.

I am hoping the group will be able to create a DIY USB->I2S board based on the XMOS cpu product. If XMOS is friendly with their audio library this may be possible. If they require restrictive licensing then a different processor will have to be looked at.

The end target is an open source ODAC with full schematics and firmware available.

[GeorgeBoudreau]

Originally Posted by fitzfish

A reference clock is necessary at any USB target device for internal circuitry that recovers the clock from the USB host interface data (desktop, laptop, etc). This reference clock is also often used as the reference clock for an internal PLL that generates the audio master clock for its Audio interfaces.

It appears that the 9023 clock is driven from the pin 3 output on the 7022 in this case

Cheers,
Dave

That is correct. The I2S signals are:
pin 1 L/R clock
pin 2 Data
pin 3 Master clock
pin 6 Bit clock

[hochopeper]

Originally Posted by GeorgeBoudreau

The reference schematic refers to the XMOS evaluation board.

George, I believe SY is asking about the ODAC design not the future opportunities for an open source design...

[GeorgeBoudreau]

If he is talking about the original ODAC I will have to get back to him later when I get some clarification.

[qusp]

UAC2 devices should be backwards compatible, so there should be no need for doing anything but the UAC2 driver. AFAIK a UAC2 device should drop back to 'UAC1.1' at 96khz if no UAC2 support is available.

[qusp]

Originally Posted by fitzfish

A reference clock is necessary at any USB target device for internal circuitry that recovers the clock from the USB host interface data (desktop, laptop, etc). This reference clock is also often used as the reference clock for an internal PLL that generates the audio master clock for its Audio interfaces.

It appears that the 9023 clock is driven from the pin 3 output on the 7022 in this case

Cheers,
Dave

I realised that after thinking about it, but I wasnt aware it had to share. thats why I asked if it was because it was shared with the MCU etc. it doesnt have to be shared with the audio clocks does it? I realise many do this, but certainly not all. the same is done with many of the UAC2 designs IE. they have a 12Mhz XO thats used for usb data and for the MCU, but anything I would consider has its own audio clocks. I presume the USB clock is needed onboard so it can act as slave sometimes too, while still acting as i2s master as in the case of async where the device. PC side design is certainly not an area I know a whole lot about