NRF52811-QCAA-R7 datasheet(132/444 Pages) NORDIC

132 / 444 page

Peripherals

Note that in a single-microphone (mono) configuration, depending on the microphone’s implementation,

either the left or the right channel (sampled at falling or rising CLK edge respectively) will contain reliable

data. If two microphones are used, one of them has to be set as left, the other as right (L/R pin tied high or

to GND on the respective microphone). It is strongly recommended to use two microphones of exactly the

same brand and type so that their timings in left and right operation match.

CLK

Vdd

DATA

L/R

CLK

DIN

nRFxxxxx

CLK

Vdd

DATA

L/R

CLK

DIN

Figure 44: Example of two PDM microphones

6.10.6 Pin configuration

The CLK and DIN signals associated to the PDM module are mapped to physical pins according to the

configuration specified in the PSEL.CLK and PSEL.DIN registers respectively. If the CONNECT field in any

PSEL register is set to Disconnected, the associated PDM module signal will not be connected to the

required physical pins, and will not operate properly.

The PSEL.CLK and PSEL.DIN registers and their configurations are only used as long as the PDM module is

enabled, and retained only as long as the device is in System ON mode. See POWER — Power supply on

page 48 for more information about power modes. When the peripheral is disabled, the pins will behave

as regular GPIOs, and use the configuration in their respective OUT bit field and PIN_CNF[n] register.

To ensure correct behaviour in the PDM module, the pins used by the PDM module must be configured

in the GPIO peripheral as described in GPIO configuration before enabling peripheral on page 132

before enabling the PDM module. This is to ensure that the pins used by the PDM module are driven

correctly if the PDM module itself is temporarily disabled or the device temporarily enters System OFF.

This configuration must be retained in the GPIO for the selected I/Os as long as the PDM module is

supposed to be connected to an external PDM circuit.

Only one peripheral can be assigned to drive a particular GPIO pin at a time. Failing to do so may result in

unpredictable behaviour.

PDM signal

PDM pin

Direction

Output value

Comment

CLK

As specified in PSEL.CLK

Output

DIN

As specified in PSEL.DIN

Input

Not applicable

Table 44: GPIO configuration before enabling peripheral

6.10.7 Registers

Base address

Peripheral

Instance

Description

Configuration

0x4001D000

PDM

Pulse-density modulation (digital

microphone interface)

Table 45: Instances

4454_140 v1.0

132

NRF52811-QCAA-R7 Datasheet(PDF) 132 Page - Nordic Semiconductor

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