
Only 6 buttons of 7 are recognized by Triggehappy:
KEY_NEXTSONG
KEY_PREVIOUSSONG
KEY_PLAYPAUSE
KEY_VOLUMEDOWN
KEY_VOLUMEUP
KEY_MIN_INTERESTING (key Headset-Mute)
Key Microphone-Mute is not recognized (or not working on my device

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and this other:
Card: C-Media USB Headphone Set
Chip: USB Mixer
Item: PCM [dB gain: -26.88, -26.88]

the three buttons on this device are recognized by Triggerhappy, so you can avoid using a USB keyboard/Keypad to control the Internet radio, instead you can use "Vol +" and "Vol -" buttons to control audio volume and the other large button to change radio stations or MP3 song (with MPD player playlist).
This is what Triggerhappy sees when you press the three buttons:
root@OpenWrt:~# thd --dump /dev/input/event*
EV_KEY KEY_VOLUMEDOWN 1 /dev/input/event1
# KEY_VOLUMEDOWN 1 command
EV_KEY KEY_VOLUMEDOWN 0 /dev/input/event1
# KEY_VOLUMEDOWN 0 command
EV_KEY KEY_VOLUMEUP 1 /dev/input/event1
# KEY_VOLUMEUP 1 command
EV_KEY KEY_VOLUMEUP 0 /dev/input/event1
# KEY_VOLUMEUP 0 command
EV_KEY KEY_MIN_INTERESTING 1 /dev/input/event1
# KEY_MIN_INTERESTING 1 command
EV_KEY KEY_MIN_INTERESTING 0 /dev/input/event1
# KEY_MIN_INTERESTING 0 command