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.