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ADMP441, SSM2529 Speech transmission

I am constructing a hearing aid for my bachelor degree project. This hearing aid will consist of a microphone with a Nordic Semiconductor nRF2460 2.4 GHz transmitter, and a receiver of samë model with a speaker. This device should filter out any unwanted frequencies outside of speech, that is anything outside of 1-5 kHz. We want to sample at 12 kHz. I and my group are designing the PCB's and power supply ourselves. For simplicity we want mostly digital signals on our PCB's. Therefore we want to use the ADMP441 which has an ADC included with an I2S interface. Our transmitter and receiver (which are the same IC), support 16 bit I2S. The SSM2529 will be our DAC and amplifier stage, and also the filter stage.

The question is, can I use the ADMP441, which supports 24 bit, to send a 16 bit signal to my 16 bit compatible transmitter?

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  • I think that there is some confusion about the clocks that we're talking about. It makes sense that the nRF2460 operates with a 256 x fs master clock, but that's probably not the rate of the CLK pin (the I2S port bit clock). Even if the nRF2460 must run at a 32 kHz sampling rate, as long as the CLK output is 64 x 32 kHz (2.048 MHz), then then ADMP441 will work directly with that I2S input port.

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  • I think that there is some confusion about the clocks that we're talking about. It makes sense that the nRF2460 operates with a 256 x fs master clock, but that's probably not the rate of the CLK pin (the I2S port bit clock). Even if the nRF2460 must run at a 32 kHz sampling rate, as long as the CLK output is 64 x 32 kHz (2.048 MHz), then then ADMP441 will work directly with that I2S input port.

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