exaU2I - Multi-Channel Asynchronous USB to I2S Interface

[AR2]

Exa, here is one aspect that I am confused about.

In the system there should be only one master clock. If we look into one possible configuration, where there is an exa board and three two channel DACs ( ESS 9012 or 9018) all on separate boards, what and how to deal with master clock? You explained earlier that your board will only allow to be configured as master unit, than what to do with DACs? Should they be all set as slaves, even though master clock always should be on DAC board? Does that mean that clocks should be omitted from DAC boards and than master clock distributed from the exa board? If that is the case should clock signal be buffered? Would your board allow for that since it demands to be master?

Does anyone knows if ESS chips allows to be switched from master to slave since they have a proprietary jitter reduction where signal entering chip is reclocked. If switched from master to slave would that eliminate the benefit that chip offers in low jitter performance?

I know, many questions, but I believe anyone using exa board will need to deal with this even if you are using ESS chip (or any other multichannel chip) in the 8 channel mode so all is on one board. I think my question applies there as well.

Your answers greatly appreciated

[qusp]

exa can be set as master or slave, ess can also be slaved or rather run fro the same clock perhaps and thus use external clock as reference for its async clocking, but i share your concerns about the distance

[egberttheone]

To eliminate the distance problem, maybe it is a idea to share the circuit diagram from the Exa so you can buy the chips separate and build your own PCB. It is possible because i think Exa want to gain money on the software instead of hardware.

[qusp]

there are other ways to eliminate distance, i have no desire or the ability to design y own product. i have already registered interest in exa, but there are still roadblocks to the ideal and this thread is about feedback to ake full version as good as it can be. so some way of mounting directly above would be best

[AR2]

Originally Posted by exa065

1. No, the I2S bus needs to use one of the build in oscillators. We have your request on the to-do list for future versions. The built-in clocks are very good and we take care to minimize jitter. ES9018 based DACs are not going to benefit from the use of external reference clock. Other DACs will.

Originally Posted by qusp

exa can be set as master or slave, ess can also be slaved or rather run fro the same clock perhaps and thus use external clock as reference for its async clocking, but i share your concerns about the distance

OK, sorry Exa, in order to respond to Qusp I looked back to one of your previous responses and actually find out that you already have answered to someone else with similar question.

Qusp, thank you for the prompt answers, but as you could see from Exa's response for now his board has to be master. I remembered that answer and that is why I posted question under assumption that exa's board is in the master mode. For anyone else looking for master distribution, I know that Acko is developing master clock distribution board. That would be needed in the scenario of running three DAC boards.

[AR2]

Originally Posted by egberttheone

To eliminate the distance problem, maybe it is a idea to share the circuit diagram from the Exa so you can buy the chips separate and build your own PCB. It is possible because i think Exa want to gain money on the software instead of hardware.

I believe exa's board will be very successfull and it will generate a great deal of interest. Next logical step will be incorporating DAC chips on the same board. Hopefully four chips in two channel mode like, ESS 9012/9018 for high end version, or ESS 9018 in eight channel mode for low end version.

[AR2]

Originally Posted by qusp

there are other ways to eliminate distance, i have no desire or the ability to design y own product. i have already registered interest in exa, but there are still roadblocks to the ideal and this thread is about feedback to ake full version as good as it can be. so some way of mounting directly above would be best

Thank you, that is a good idea.

[RayCtech]

Originally Posted by AR2

OK, sorry Exa, in order to respond to Qusp I looked back to one of your previous responses and actually find out that you already have answered to someone else with similar question.

Qusp, thank you for the prompt answers, but as you could see from Exa's response for now his board has to be master. I remembered that answer and that is why I posted question under assumption that exa's board is in the master mode. For anyone else looking for master distribution, I know that Acko is developing master clock distribution board. That would be needed in the scenario of running three DAC boards.

You can run as many ES9018 boards you like without any I2S issues.
The bit and word clock from the exaU2I are the only clocks that matters.
It is the word clock that latches the data into the ES9018.

The only issue that could cause problems are if you control all ES9018 boards from one I2C master, and then only if you write to registers in all ES9018 in parallel with the identical I2C address on all the ES9018 boards.

For I2S there are no problems.

[AR2]

Originally Posted by RayCtech

You can run as many ES9018 boards you like without any I2S issues.
The bit and word clock from the exaU2I are the only clocks that matters.
It is the word clock that latches the data into the ES9018.

The only issue that could cause problems are if you control all ES9018 boards from one I2C master, and then only if you write to registers in all ES9018 in parallel with the identical I2C address on all the ES9018 boards.

For I2S there are no problems.

Thank you RayCtech. If I do understand you well, with exa board and one DAC per two channels, this really is not going to be an issue, since every DAC will have its own I2S line?

[qusp]

yes thats correct he did say that, i'm aware of the earlier response, but i have private information to the contrary with a few caveats, in its current form its not a straight forward thing because exa has 2 clocks. i probably shouldnt post more here though, perhaps exa will chime in.

also sabre dacs only can choose from a maximum of 2 i2c addresses with onboard mcu, there needs to be an external controller to facilitate more dacs to be controlled, however if crossover is implemented via software before titan, or within titan itself there will be no issue as they do not need to talk to each other