nRF52840 Maximum I2S Settings

RE: nRF52840 Maximum I2S Settings

haakonsh — Thu, 03 May 2018 06:47:07 GMT

Most likely, it's derived from MCK.

RE: nRF52840 Maximum I2S Settings

rpriddell — Wed, 02 May 2018 15:44:41 GMT

Thanks for the response. How about the restriction on 48 kHz for the frame clock? Is it also a duty cycle issue?

RE: nRF52840 Maximum I2S Settings

haakonsh — Wed, 02 May 2018 11:34:52 GMT

-Edit

The duty cycle goes out of I2S spec (45-55%) above 4MHz, to 60-70%.

RE: nRF52840 Maximum I2S Settings

rpriddell — Mon, 30 Apr 2018 15:46:14 GMT

What drives this though? The configuration examples and register settings indicate you can use a divisor smaller than 8. Empirically I can set it up with a divisor producing an MCLK of 8 MHz and I see no issues on the clock edges. Is this a true limitation, or is there lack of production testing to verify it will work?

RE: nRF52840 Maximum I2S Settings

haakonsh — Sat, 28 Apr 2018 15:47:43 GMT

4MHz is the specified limit, even when operating in slave mode.

RE: nRF52840 Maximum I2S Settings

haakonsh — Sat, 28 Apr 2018 15:37:41 GMT

Hey massimo,

4MHz is the limit for MCK. The MCK is derived from the 32MHz clock and a divisor. In the SDK example the default config is 32MHz /8 = 4MHz.

Cheers,
Håkon H.

RE: nRF52840 Maximum I2S Settings

rpriddell — Fri, 27 Apr 2018 20:14:45 GMT

One further datapoint to add... I would only be interested in the nordic master receiving data over I2S and do not need the transmit path to work. So if there is some restriction on Master TX, i needn't be concerned.

Nordic as Master, I2S Format, Mono, Nordic Rx only (no transmit needed), 62.5 kHz frame clock with 8 MHz master clock desired, 16 bit width.

RE: nRF52840 Maximum I2S Settings

rpriddell — Thu, 26 Apr 2018 07:55:39 GMT

I should also note that my application would be I2s format mono, not stereo.