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| Supported Targets | ESP32 | ESP32-C3 | ESP32-C6 | ESP32-S3 |
| ----------------- | ----- | -------- | -------- | -------- |
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# I2S Basic PDM Mode Example
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(See the README.md file in the upper level 'examples' directory for more information about examples.)
This example is going to show how to use the PDM TX and RX mode.
## How to Use Example
### Hardware Required
#### General
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* A development board with any supported Espressif SOC chip (see `Supported Targets` table above)
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* A USB cable for power supply and programming
#### PDM RX
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* For non-ESP32-S3 SoC, a PDM microphone whose `sel` pin is supposed to be pulled down, and connecting its `clk` pin to `EXAMPLE_PDM_RX_CLK_IO` , `data` pin to `EXAMPLE_PDM_RX_DIN_IO` .
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```
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┌───────────────────────┐ ┌──────────────────┐
│ ESP │ │ PDM microphone │
│ │ PDM clock │ │
│ EXAMPLE_PDM_RX_CLK_IO ├──────────────►│ CLK │
│ │ PDM data │ │
│ EXAMPLE_PDM_RX_DIN_IO │◄──────────────┤ DATA │
│ │ │ │
│ │ ┌─────┤ SEL │
│ │ │ │ │
│ GND ├─────────┴─────┤ GND │
│ │ │ │
│ VCC ├───────────────┤ VCC │
└───────────────────────┘ └──────────────────┘
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```
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* For ESP32-S3 SoC, this example shows how to support 8 PDM microphones, in this case, the connection can be:
```
┌──────────────────┐ ┌─────────────────────────┐ ┌──────────────────┐
│ PDM microphone3 │ │ ESP │ │ PDM microphone1 │
│ │ PDM clock │ │ PDM clock │ │
│ CLK │◄───┬───────────────────┤ EXAMPLE_PDM_RX_CLK_IO ├───────────────────┬───►│ CLK │
│ │ │ │ │ │ │ │
│ DATA ├────┼────┐ │ EXAMPLE_PDM_RX_DIN_IO │◄─────────────┬────┼────┤ DATA │
│ │ │ │ │ │ │ │ │ │
│ SEL ├────┼────┼─────────┐ │ │ ┌─────────┼────┼────┤ SEL │
│ │ │ │ │ │ │ │ │ │ │ │
│ GND ├────┼────┼────┐ │ │ │ │ ┌────┼────┼────┤ GND │
│ │ │ │ │ │ │ │ │ │ │ │ │ │
│ VCC ├────┼────┼────┼────┤ │ │ ├────┼────┼────┼────┤ VCC │
└──────────────────┘ │ │ │ │ │ │ │ │ │ │ └──────────────────┘
│ │ │ │ │ │ │ │ │ │
┌──────────────────┐ │ │ │ │ │ │ │ │ │ │ ┌──────────────────┐
│ PDM microphone4 │ │ │ │ │ │ │ │ │ │ │ │ PDM microphone2 │
│ │ │ │ │ │ │ │ │ │ │ │ │ │
│ CLK │◄───┤ │ │ │ │ │ │ │ │ ├───►│ CLK │
│ │ │ │ │ │ │ │ │ │ │ │ │ │
│ DATA ├────┼────┴────┼────┼───►│ EXAMPLE_PDM_RX_DIN1_IO │ │ │ └────┼────┤ DATA │
│ │ │ │ │ │ │ │ │ │ │ │
│ SEL ├────┼─────────┤ │ │ │ │ ├─────────┼────┤ SEL │
│ │ │ │ │ │ │ │ │ │ │ │
│ GND ├────┼─────────┤ │ │ │ │ ├─────────┼────┤ GND │
│ │ │ │ │ │ │ │ │ │ │ │
│ VCC ├────┼─────────┼────┤ │ │ ├────┼─────────┼────┤ VCC │
└──────────────────┘ │ │ │ │ │ │ │ │ └──────────────────┘
│ │ │ │ │ │ │ │
┌──────────────────┐ │ │ │ │ │ │ │ │ ┌──────────────────┐
│ PDM microphone7 │ │ │ │ │ │ │ │ │ │ PDM microphone5 │
│ │ │ │ │ │ │ │ │ │ │ │
│ CLK │◄───┤ │ │ │ │ │ │ ├───►│ CLK │
│ │ │ │ │ │ │ │ │ │ │ │
│ DATA ├────┼────┐ │ │ │ EXAMPLE_PDM_RX_DIN2_IO │◄───┼────┼────┬────┼────┤ DATA │
│ │ │ │ │ │ │ │ │ │ │ │ │ │
│ SEL ├────┼────┼────┼────┤ │ │ ├────┼────┼────┼────┤ SEL │
│ │ │ │ │ │ │ │ │ │ │ │ │ │
│ GND ├────┼────┼────┤ │ │ │ │ ├────┼────┼────┤ GND │
│ │ │ │ │ │ │ │ │ │ │ │ │ │
│ VCC ├────┼────┼────┼────┤ │ │ ├────┼────┼────┼────┤ VCC │
└──────────────────┘ │ │ │ │ │ │ │ │ │ │ └──────────────────┘
│ │ │ │ │ │ │ │ │ │
┌──────────────────┐ │ │ │ │ │ │ │ │ │ │ ┌──────────────────┐
│ PDM microphone8 │ │ │ │ │ │ │ │ │ │ │ │ PDM microphone6 │
│ │ │ │ │ │ │ │ │ │ │ │ │ │
│ CLK │◄───┘ │ │ │ │ │ │ │ │ └───►│ CLK │
│ │ │ │ │ │ │ │ │ │ │ │
│ DATA ├─────────┴────┼────┼───►│ EXAMPLE_PDM_RX_DIN3_IO │ │ │ └─────────┤ DATA │
│ │ │ │ │ │ │ │ │ │
│ SEL ├──────────────┤ │ │ │ │ ├──────────────┤ SEL │
│ │ │ │ │ │ │ │ │ │
│ GND ├──────────────┴────┼────┤ GND ├────┼────┴──────────────┤ GND │
│ │ │ │ │ │ │ │
│ VCC ├───────────────────┴────┤ VCC ├────┴───────────────────┤ VCC │
└──────────────────┘ └─────────────────────────┘ └──────────────────┘
```
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#### PDM TX
* An earphone or a speaker
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* An audio power amplifier that can input PDM signal. If the power amplifier can only receive the analog signal without PDM clock, a low-pass passive or active filter is required to restore the PDM data wave into analog signal, before it is transmitted to the power amplifier.
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**MAX98358**
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Please refer to the [Datasheet of MAX98358 ](https://datasheets.maximintegrated.com/en/ds/MAX98358.pdf ) for more details.
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```
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┌────────────────────────┐ ┌───────────────┐
│ ESP │ │ MAX 98358 │
│ │ PDM clock │ │
│ EXAMPLE_PDM_TX_CLK_IO ├──────────────►│ CLK │ ┌─────────┐
│ │ PDM data │ │ │ Speaker │
│ EXAMPLE_PDM_TX_DOUT_IO ├──────────────►│ DATA OUTP ├───┤ │
│ │ │ │ │ │
│ │ ┌─────┤ SD_MODE OUTN ├───┤ │
│ │ │ │ │ │ │
│ VCC ├─────────┴─────┤ VCC │ └─────────┘
│ │ │ │
│ GND ├───────────────┤ GND │
└────────────────────────┘ └───────────────┘
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```
**NS4150**
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Please refer to the [Datasheet of NS4150 ](http://www.nsiway.com.cn/product/44.html ) for more details.
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```
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┌────────────────────────┐ ┌───────────────┐
│ ESP │ │ NS 4150 │
│ │ │ │
│ EXAMPLE_PDM_TX_CLK_IO │(No need to connect) │ INN │ ┌─────────┐
│ │PDM data┌────────────────┐ │ │ │ Speaker │
│ EXAMPLE_PDM_TX_DOUT_IO ├────────┤ Low-pass Filter├───►│ INP VoP ├───┤ │
│ │ └────────────────┘ │ │ │ │
│ │ ┌───┤ CTRL VoN ├───┤ │
│ │ │ │ │ │ │
│ VCC ├──────────────────────────┴───┤ VCC │ └─────────┘
│ │ │ │
│ GND ├──────────────────────────────┤ GND │
└────────────────────────┘ └───────────────┘
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```
### Configure the Project
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PDM can only works in simplex mode, you can select the PDM direction in the menu config, or just setting the macro `EXAMPLE_PDM_DIR` directly. Setting it to `EXAMPLE_PDM_TX` or `EXAMPLE_PDM_RX` can choose the PDM direction of this example. But currently ESP32-C3 does not support PDM RX mode.
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### Build and Flash
Build the project and flash it to the board, then run monitor tool to view serial output:
```
idf.py -p PORT build flash monitor
```
(To exit the serial monitor, type ``Ctrl-]``.)
See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.
## Example Output
### PDM TX
While `EXAMPLE_PDM_DIR` is set to `EXAMPLE_PDM_TX` , then you can see the following log:
```
I2S PDM TX example start
---------------------------
D (284) i2s_common: tx channel is registered on I2S0 successfully
D (294) i2s_common: DMA malloc info: dma_desc_num = 6, dma_desc_buf_size = dma_frame_num * slot_num * data_bit_width = 500
D (304) i2s_pdm: Clock division info: [sclk] 160000000 Hz [mdiv] 3 [mclk] 49152000 Hz [bdiv] 8 [bclk] 6144000 Hz
D (314) i2s_pdm: The tx channel on I2S0 has been initialized to PDM TX mode successfully
D (324) i2s_common: i2s tx channel enabled
Playing bass `twinkle twinkle little star`
Playing alto `twinkle twinkle little star`
Playing treble `twinkle twinkle little star`
...
```
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You can hear the audio 'twinkle twinkle little star' in three tones if you connect a speaker to it.
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### PDM RX
While `EXAMPLE_PDM_DIR` is set to `EXAMPLE_PDM_RX` , but without connecting a PDM microphone, then you can see the following log:
```
I2S PDM RX example start
---------------------------
D (10) i2s_common: rx channel is registered on I2S0 successfully
D (10) i2s_common: DMA malloc info: dma_desc_num = 6, dma_desc_buf_size = dma_frame_num * slot_num * data_bit_width = 500
D (20) i2s_common: i2s rx channel enabled
Read Task: i2s read 2048 bytes
-----------------------------------
[0] -6595 [1] 0 [2] -29199 [3] -32768
[4] -30203 [5] -32156 [6] -30704 [7] -31348
Read Task: i2s read 2048 bytes
-----------------------------------
[0] -30935 [1] -30935 [2] -30935 [3] -30935
[4] -30935 [5] -30935 [6] -30935 [7] -30935
Read Task: i2s read 2048 bytes
-----------------------------------
[0] -30935 [1] -30935 [2] -30935 [3] -30935
[4] -30935 [5] -30935 [6] -30935 [7] -30935
```
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And only if you connect a PDM microphone, you can see the data changes:
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```
I2S PDM RX example start
---------------------------
D (10) i2s_common: rx channel is registered on I2S0 successfully
D (10) i2s_common: DMA malloc info: dma_desc_num = 6, dma_desc_buf_size = dma_frame_num * slot_num * data_bit_width = 500
D (20) i2s_common: i2s rx channel enabled
Read Task: i2s read 2048 bytes
-----------------------------------
[0] -3181 [1] 0 [2] -7194 [3] -24288
[4] -777 [5] 3650 [6] 109 [7] 571
Read Task: i2s read 2048 bytes
-----------------------------------
[0] 2391 [1] 2378 [2] 2397 [3] 2385
[4] 2399 [5] 2375 [6] 2401 [7] 2389
```
## Troubleshooting
For any technical queries, please open an [issue ](https://github.com/espressif/esp-idf/issues ) on GitHub. We will get back to you soon.
