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3.5mm Headphone Jack

The Radxa CM4 IO Board features a built-in 3.5mm 4-pole headphone jack that supports both audio input and output.

Hardware Connection​

Insert your 3.5mm headphone plug into the headphone jack on the Radxa CM4 IO Board.

tip

Refer to the Hardware Information guide to locate the headphone jack.

Audio Testing​

View Audio Devices​

Use the aplay -l command to view audio playback devices (speakers), and arecord -l to view audio recording devices (microphone).

  • View Playback Devices
radxa@device$
aplay -l

Terminal output example: The onboard ES8388 audio codec (card 1: rockchipes8388) is typically used for both input (microphone) and output (audio playback) through the 3.5mm headphone jack.

card 0: rockchiphdmi0 [rockchip-hdmi0], device 0: rockchip-hdmi0 i2s-hifi-0 [rockchip-hdmi0 i2s-hifi-0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: rockchipes8388 [rockchip-es8388], device 0: dailink-multicodecs ES8323 HiFi-0 [dailink-multicodecs ES8323 HiFi-0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
  • View Recording Devices
radxa@device$
arecord -l

Example output: The onboard ES8388 audio codec (card 1: rockchipes8388) is typically used for both input (microphone) and output (audio playback) through the 3.5mm headphone jack.

radxa@device$
card 0: rockchiphdmi0 [rockchip-hdmi0], device 0: rockchip-hdmi0 i2s-hifi-0 [rockchip-hdmi0 i2s-hifi-0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: rockchipes8388 [rockchip-es8388], device 0: dailink-multicodecs ES8323 HiFi-0 [dailink-multicodecs ES8323 HiFi-0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

Record Audio​

This feature requires headphones with microphone support. Use the arecord command to record audio.

radxa@device$
sudo arecord -Dhw:1,0 -d 20 -f cd -r 44100 -c 2 -t wav /tmp/tmp.wav
  • -Dhw:1,0: Use device 0 of card 1: rockchipes8388
  • -d 20: Record for 20 seconds
  • -f cd: Use CD audio format (16-bit little-endian, 44100 Hz, stereo)
  • -r 44100: Use 44.1kHz sample rate
  • -c 2: Use stereo (2 channels)
  • -t wav: Output in WAV format
  • /tmp/tmp.wav: Output file path

Play Audio​

Use the aplay command to play audio.

radxa@device$
sudo aplay -Dhw:1,0 /tmp/tmp.wav
  • -Dhw:1,0: Use device 0 of card 1: rockchipes8388
  • /tmp/tmp.wav: Input file path to play

Interface Pin Definitions​

For detailed pin definitions, please refer to the hardware schematics available on the Resource Download page.