ANC hardware selection

Hello,

I'm working on implementing an active noise control algorithm. I am currently working on an ADSP-221489 EZKIT LITE, because we had one lying around. I am quite new to these things, but I am beginning to suspect that this board and the AD1939 codec on it are not quite suited to my application. I got the algorithm to work, but I feel the system is not working as well as it could be, mainly due to latency issues. I am wondering which hardware would be better for me. I hope you can help. Below I have listed some information about my application:

- Active noise control system with adaptive controller and adaptive plant model.

- Preferred sample frequency: 8 kHz.

- 2 ADCs/input ports.

- 2 DACs/output ports.

- Low latency (currently multiple ms's)

If you need more specific details to answer my question, please let me know.

Regards,

Thijs

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  • Hello Thijs,

    Sorry, I was answering too quickly and going from memory. The AD1939 group delay for the DAC is 521us (not ms) and the ADC is 479us so add to that another 20us (roughly) to transmit the data in one clock period and another 20us to transmit back to the DAC and you are around 1.04ms. So adding to that any processing you are doing and I can see you would get around 1.5ms total latency.

    So back to your questions. The slower sample rate is good for less processing but the problem is that it takes 125us just to transmit the data in one direction. So using a slower sampling rate may be creating more problems then it is solving. This is obviously your design decisions, I am just pointing it out and I do not see the big picture.

    Regarding trying out the ADAU1772. You can purchase an eval board. It is a relatively low cost board. Then you can jumper between the I2S headers on both eval boards. Since the 1772 uses ASRCs you can use the MCLK on the eval board to drive the 1772 so you do not have to supply the MCLK. I am not that familiar with the EZkit but I am fairly certain that the SPORTS come up to headers to allow you to interface to an external board.

    Dave T

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  • Hello Thijs,

    Sorry, I was answering too quickly and going from memory. The AD1939 group delay for the DAC is 521us (not ms) and the ADC is 479us so add to that another 20us (roughly) to transmit the data in one clock period and another 20us to transmit back to the DAC and you are around 1.04ms. So adding to that any processing you are doing and I can see you would get around 1.5ms total latency.

    So back to your questions. The slower sample rate is good for less processing but the problem is that it takes 125us just to transmit the data in one direction. So using a slower sampling rate may be creating more problems then it is solving. This is obviously your design decisions, I am just pointing it out and I do not see the big picture.

    Regarding trying out the ADAU1772. You can purchase an eval board. It is a relatively low cost board. Then you can jumper between the I2S headers on both eval boards. Since the 1772 uses ASRCs you can use the MCLK on the eval board to drive the 1772 so you do not have to supply the MCLK. I am not that familiar with the EZkit but I am fairly certain that the SPORTS come up to headers to allow you to interface to an external board.

    Dave T

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