My way of getting Trus Mico to work reasonably on FreeBSD was using pulseaudio, and remapping the pulseaudio input source to mono.



First look in the dmesg to identify where the device ends up:



per@konjak:/usr/home/per$ dmesg | grep uaudio
uaudio0 on uhub2
uaudio0: on usbus0
uaudio0: No playback.
uaudio0: Record[0]: 48000 Hz, 1 ch, 16-bit S-LE PCM format, 2x8ms buffer.
uaudio0: Record[0]: 44100 Hz, 1 ch, 16-bit S-LE PCM format, 2x8ms buffer.
uaudio0: Record[0]: 24000 Hz, 1 ch, 16-bit S-LE PCM format, 2x8ms buffer.
uaudio0: Record[0]: 22050 Hz, 1 ch, 16-bit S-LE PCM format, 2x8ms buffer.
uaudio0: Record[0]: 16000 Hz, 1 ch, 16-bit S-LE PCM format, 2x8ms buffer.
uaudio0: Record[0]: 11025 Hz, 1 ch, 16-bit S-LE PCM format, 2x8ms buffer.
uaudio0: Record[0]: 8000 Hz, 1 ch, 16-bit S-LE PCM format, 2x8ms buffer.
uaudio0: No MIDI sequencer.
pcm3: on uaudio0
uaudio0: No HID volume keys found.
uaudio1 on uhub0
uaudio1: on usbus0
uaudio1: Play[0]: 48000 Hz, 2 ch, 16-bit S-LE PCM format, 2x8ms buffer.
uaudio1: Play[0]: 44100 Hz, 2 ch, 16-bit S-LE PCM format, 2x8ms buffer.
uaudio1: Record[0]: 48000 Hz, 1 ch, 16-bit S-LE PCM format, 2x8ms buffer.
uaudio1: Record[0]: 44100 Hz, 1 ch, 16-bit S-LE PCM format, 2x8ms buffer.
uaudio1: No MIDI sequencer.
pcm4: on uaudio1
uaudio1: HID volume keys found.


Trust Mico is the C-Media device on uaudio1 in this case


As you can see, uadio1 ends up on pcm4


Now we know that the Trus Mico is the C-Media device on uaudio1, and that uaudio1 is connected to pcm4


In case you have pulseaudio installed, you can try this in a terminal:


pactl list sources



Somewhere in the output I found:



Source #6
State: RUNNING
Name: oss_input.dsp4
Description: /dev/dsp4
Driver: module-oss.c
Sample Specification: s16le 2ch 48000Hz
Channel Map: front-left,front-right
Owner Module: 10
Mute: no
Volume: front-left: 0 / 0%, front-right: 0 / 0%
balance 0.00
Base Volume: 65536 / 100%
Monitor of Sink: n/a
Latency: 6083 usec, configured 85333 usec
Flags: HARDWARE HW_VOLUME_CTRL LATENCY
Properties:
device.string = "/dev/dsp4"
device.api = "oss"
device.description = "/dev/dsp4"
device.access_mode = "mmap"
device.buffering.buffer_size = "16384"
device.buffering.fragment_size = "4096"
device.icon_name = "audio-input-microphone"
Formats:
pcm


/dev/dsp4 is the dsp corresponding to the pcm4 device


The pulseaudio source name for this device is listed as:
oss_input.dsp4

Now one can try:

pactl load-module module-remap-source source_name=mono master=oss_input.dsp4

In case everything works, now a new input source should be available after starting pavucontrol.

Now I can set the volume on the new input source (I have it around 125%)

I really hope this works for you too