Hardware example

nRF5340 Product Specification

PDM can be configured with a single microphone (mono), or with two microphones.

When a single microphone is used, connect the microphone clock to CLK, and data to DIN.

Figure 5. Example of a single PDM microphone, wired as left
Page-1 Sheet.83 Sheet.84 Sheet.85 Sheet.86 Sheet.87 Sheet.88 Sheet.89 Sheet.90 CLK CLK Sheet.91 Vdd Vdd Sheet.92 DATA DATA Sheet.93 L/R L/R Sheet.94 Sheet.95 Sheet.96 Sheet.97 Sheet.98 Sheet.99 CLK CLK Sheet.100 DIN DIN Sheet.101 nRFxxxxx nRFxxxxx Sheet.102 Page-1 Sheet.5 Sheet.6 Sheet.7 CLK CLK Sheet.8 DIN DIN Sheet.9 Sheet.10 Sheet.11 Sheet.12 Sheet.13 Sheet.14 Sheet.15 Sheet.16
Figure 6. Example of a single PDM microphone, wired as right
Page-1 Sheet.129 Sheet.130 Sheet.131 Sheet.132 Sheet.133 Sheet.134 Sheet.135 CLK CLK Sheet.136 Vdd Vdd Sheet.137 DATA DATA Sheet.138 L/R L/R Sheet.139 Sheet.140 Sheet.141 Sheet.142 Sheet.143 Sheet.144 CLK CLK Sheet.145 DIN DIN Sheet.146 nRFxxxxx nRFxxxxx Sheet.147 Page-1 Sheet.17 Sheet.18 Sheet.19 Sheet.20 Sheet.21 Sheet.22 Sheet.23 Sheet.24 Sheet.25 CLK CLK Sheet.26 DIN DIN Sheet.27 Sheet.28 Sheet.29

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.

Figure 7. Example of two PDM microphones
Example of two PDM microphones Page-1 Sheet.30 Sheet.31 Sheet.32 CLK CLK Sheet.33 DIN DIN Sheet.34 Sheet.35 Sheet.36 Sheet.37 Sheet.38 Sheet.39 Sheet.40 Sheet.41 Sheet.42 Sheet.43 Sheet.44