140 PDM microphone
140 : PDM microphone
- Author: Jon Nordby & Martin Stensgård
- Description: PDM microphone
- GitHub repository
- Open in 3D viewer
- Clock: 64000000 Hz
How it works
The PDM peripheral outputs a bit clock signal for a PDM microphone, and decodes the returned density signal into Pulse Code Modulation (PCM) words.
Register map
| Address | Name | Access | Description |
|---|---|---|---|
| 0x00 | ENABLE | R/W | Clock gate (0-1). |
| 0x04 | PERIOD | R/W | PDM clock period (0-255). |
| 0x08 | SELECT | R/W | PDM data pin number (0-7). |
| 0x0c | SAMPLE | R | PCM sample, result of conversion. |
ENABLE
Bit 0: Enable clock generation.
PERIOD
Number of system clock cycles per PDM clock cycle. For example, to generate a 1 MHz clock signal, set this to 64.
SELECT
Which input pin to sample data on.
SAMPLE
16-bit signed integer. Clears interrupt when read.
How to test
Connect PDM microphone using DATA and CLK.
Configure the clock rate using PERIOD, and turn the clock on using ENABLE.
External hardware
A PDM microphone is needed. It is most practical to use a microphone on a breakout board. We have tested with AdaFruit PDM MEMS microphone breakout, which has a MP34DT01-M microphone.
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | PDM clock | ||
| 1 | PDM data | ||
| 2 | |||
| 3 | |||
| 4 | |||
| 5 | |||
| 6 | |||
| 7 |