i2S digital microphone with nRF52832

[worldsnexthero]

I am using a digital microphone using i2S interface with the following signals: BCLK (bit clock), WS (word strobe), SELECT (select for Left/Right) and SDOUT (digital data output).

On nRF52 there are five main signals for i2S including MCLK, LRCLK, SCLK, SDIN and SDOUT.

How are these signals mapped to each other, in particular the MCLK?

Thanks, Faizan

[Anders Strand]

Hello.

The i2s peripheral on the nRF52 is made to cover all use cases. You do not have to use all pins on the nRF52. You can disable the pins you do not need. You can find the documentation of the nRF52 i2s peripheral here, you should read that if you haven't.

You should connect your microphone like this:

Microphone - nRF52
BCLK       - SCLK
WS         - LRCLK
STDOUT     - SDIN 
SELECT     - GND / VDD

I am not sure what WS is, can you post a link to the microphone?

UPDATE April 1st. 2016:

After investigating the data sheet, i now understand the relation between WS and SELECT.WS is to alternate for every frame, and toggle between left and right. When you have two microphones on the same i2s bus, this will toggle between the two microphones. But how do the microphones know if they are left or right? This is where SELECT comes in. Pull the SELECT on one mic to GND, and the SELECT of the other mic to VDD. The microphones will send audio when the WS input matches the SELECT value. This means that WS should be connected to LRCLK, not SELECT as i though before reading the data sheet of the mic. I have updated the above "table". Read about this on page 6 and 7 in the data sheet.

-Anders

[worldsnexthero]

Thanks for your explanation. This makes sense, however I am still unsure about the WS pin. Here is the datasheet of the microphone I'm using:

www.knowles.com/.../SPH0645LM4H-BRevB.PDF

Thanks a lot.

[Anders Strand]

See the updated answer

[Sheikh_Khaled_Dubai]

where are the pins in the nRF52 for : SCLK LRCLK SDIN thnx a lot !!

[NewtoM]

Hi Khaled,

check out the I2S example in the SDK. You will find a line err_code = nrf_drv_i2s_init(&config, data_handler); in the main. If you track down config, you will see it has the type nrf_drv_i2s_config_t and the default values stored in NRF_DRV_I2S_DEFAULT_CONFIG. Now it you look at that more precisely in nrf_drv_i2s.h then you will see that the pins have following values:

#define I2S_CONFIG_SCK_PIN      22
#define I2S_CONFIG_LRCK_PIN     23
#define I2S_CONFIG_SDIN_PIN     25

as defined in nrf_drv_config.h.

Look here to see where those pins are on the development board.

I hope that helps.

NewtoM