ap09 copies loops between an Ammoon AP-09 nano looper and a Linux computer over the pedal's USB cable: download the loop as WAV, listen to it, put any audio file on the pedal, bring back older loops still in memory. It comes as a command-line tool (ap09) and a GTK 4 app (ap09-gui).

The pedal has no Linux software, and the existing open-source tool does not work with it. Its USB protocol was reverse-engineered from the vendor's Windows program. Everything here was written from scratch.

Which pedal

The Ammoon AP-09 nano looper: a small white pedal with one LEVEL knob, a footswitch, a 9 V jack and a USB port on the top. Plugged into a computer it shows up as USB ID 0416:5555 (lsusb calls it "Winbond Electronics Corp. DFU"). Only this model has been tested; see Troubleshooting for similar pedals.

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Features

	Status
Download the current loop → WAV	✅ verified bit-exact
List and download older loops still in memory	✅
Listen to any loop on the computer	✅
Upload WAV / MP3 / FLAC / … → pedal	✅ bit-exact over USB · ⚠️ playback on the pedal not yet confirmed (why)
Cut the file before upload: start/end, or BPM × bars for a loop exactly in time	✅
Make an older loop play again (select)	✅
Delete loops from the list, clear the pedal	✅
Free space scan, device info	✅
Graphical app: waveforms, drag & drop upload, compact sidebar layout	✅

Narrow window, sidebar open	Upload preview with cut
About

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Why this exists

In November 2017 I wanted to get my loops off an Ammoon AP-09 on Linux. The only open-source tool for these cheap looper pedals was reinerh/loopertrx, so I tried it. It answered DEVICE NOT FOUND. I opened loopertrx issue #1 — "Ammoon Looper AP-09" with the lsusb and kernel output. It never got a reply and is still open.

Years later I looked again at why it could not work. There were two reasons, and only the first one is easy to fix:

1. Wrong USB ID. loopertrx was written for the Harley Benton Mini Looper and looks for USB ID 0483:572a. The AP-09 is 0416:5555 (a Rowin OEM chip that shows up as "Winbond … DFU"), so the device is never found.
2. Wrong protocol. With the ID patched in, loopertrx finds the pedal but its handshake times out. loopertrx speaks a mass-storage-style protocol (USBC command blocks over bulk endpoints). The AP-09 is a USB-MIDI device that talks SysEx. A later report on the same chip, loopertrx issue #6 (Rowin Twin Looper), showed one working SysEx message, and nothing more.

The vendor's own software ("LooperSuite") is Windows-only and crashes under Wine. So I disassembled it, worked out the SysEx packet format, the pedal's flash commands, the NAND layout and the loop index, tested every step live on the pedal, and wrote a new tool around that. The details are in docs/PROTOCOL.md.

Issue #1 stays the starting point: if you arrive here from it, this is the answer.

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Install

Quick install (Debian, Ubuntu, Mint, …)

git clone https://github.com/wdog/ap09-tool.git
cd ap09-tool
./install.sh

The script asks before each step that needs sudo. It:

1. offers to install the system packages that are missing (python3-usb pipx ffmpeg python3-gi gir1.2-gtk-4.0 gir1.2-adw-1 gir1.2-gstreamer-1.0 gstreamer1.0-plugins-good python3-numpy);
2. installs the ap09 and ap09-gui commands with pipx into ~/.local/bin;
3. adds AP-09 Looper with its icon to the app menu;
4. installs the udev rule /etc/udev/rules.d/60-ap09.rules, so the pedal works without sudo. Unplug and replug the pedal afterwards.

Options: ./install.sh --no-udev skips the udev rule, ./install.sh --uninstall removes everything it installed. To upgrade, git pull and run ./install.sh again.

Manual install / other distributions

The CLI only needs Python ≥ 3.11 and pyusb; ffmpeg is used to convert non-WAV files on upload. The GUI also needs PyGObject with GTK 4, libadwaita ≥ 1.5, GStreamer (with the "good" plugins) and numpy. Take those from your distribution, then:

pipx install --system-site-packages .       # or: pip install --user .
sudo install -m644 data/60-ap09.rules /etc/udev/rules.d/
sudo udevadm control --reload && sudo udevadm trigger

distribution	packages
Debian / Ubuntu	python3-usb pipx ffmpeg python3-gi gir1.2-gtk-4.0 gir1.2-adw-1 gir1.2-gstreamer-1.0 gstreamer1.0-plugins-good python3-numpy
Fedora	python3-pyusb pipx ffmpeg python3-gobject gtk4 libadwaita gstreamer1-plugins-good python3-numpy
Arch	python-pyusb python-pipx ffmpeg python-gobject gtk4 libadwaita gst-plugins-good python-numpy

Run from the source folder, without installing

python3 ap09.py info
python3 ap09_gui.py

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Quick start

Plug the pedal in with its USB cable. No special mode is needed.

ap09 info                     # what is on the pedal
ap09 download myloop.wav      # save the current loop
ap09 upload song.mp3          # put an audio file on the pedal

After upload, select, delete or clear, unplug and replug the pedal so it loads the change. Or open AP-09 Looper from the app menu and do the same with the mouse.

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The app (ap09-gui)

• Detects the pedal when you plug it in (checks every 2 s).
• Sidebar: Upload (click or drop a file), free-space scan (about 4 min) with a level bar, actions (download all loops to a folder, clear, open the cache folder, about) and device details. On a narrow window it folds away: open it with the sidebar button or F9.
• On the pedal: the current loop with length, waveform, ▶ play, 💾 save as WAV, ✖ clear.
• Upload: drag an audio file anywhere onto the window, or click Upload in the sidebar (Ctrl+O). You see a preview with waveform and length, then confirm. There you can cut the file: set start/end (or click the waveform), or give a BPM and a number of bars so the loop is exactly that long; ▶ plays the cut looped. Progress with % and ETA, and a safe Cancel.
• Loops: every older loop with its state, a small waveform, ▶, 💾, ↩ put on pedal and 🗑 delete.
• Player bar: play/pause, click the waveform to seek, stop.
• Keys: F5 refresh · F9 sidebar · Space play/pause · Ctrl+O upload.

All pedal access runs on one background thread, so the window never freezes.

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The command line (ap09)

Run ap09 -h or ap09 COMMAND -h for all options.

command	what it does
ap09 info	device, model and current loop
ap09 list [--all]	current loop and older loops in memory (--all shows deleted ones)
ap09 play [-r N]	listen on the computer (current loop, or loop #N)
ap09 download [-r N] FILE.wav	save a loop as WAV; -a DIR saves all of them
ap09 upload FILE	put any audio file on the pedal
ap09 select N	make loop #N the one the pedal plays
ap09 delete N	remove loop #N from the list
ap09 clear	leave the pedal without a loop
ap09 space	count free memory (full scan, about 4 min)
ap09 about, ap09 -V	version, author, license

Show what is on the pedal

$ ap09 info
device  0416:5555  bus 3 addr 16
model   0x2715 NANO LOOPER
info    abcdefghabcdefgh 01 00 05 12 13 14 15 16 17 18 19
format  mono  24-bit  46875 Hz
loop    ▶ 19.91 s
size    2799858 B  22 blocks  first 1661
index   record @ +0xc000  seq 0x696

List the loops

The pedal plays one loop. Its index also remembers the loops you recorded before, and their audio usually stays in memory until it gets reused. Loop numbers never change.

$ ap09 list
▶ playing #3  19.91 s

 #    length  blocks  state
 0   13.93 s      15  ● in memory
 1    7.94 s       9  ⚠ damaged 3/9
 3   19.91 s      22  ▶ playing

icon	state	meaning
▶	playing	the loop the pedal plays
●	in memory	older loop, audio still there: download -r N, select N
⚠	damaged N/M	older loop, N of M blocks overwritten by a later loop
✖	deleted	removed with clear / delete (shown with list --all)
■	no loop	pedal empty or cleared

Colours are used on a terminal; set NO_COLOR=1 to turn them off.

Download

ap09 download myloop.wav          # current loop
ap09 download -r 3 old3.wav       # loop #3 from 'list'
ap09 download -a myloops/         # every loop into a folder

About 12 s for a 20 s loop. The file is exactly what the pedal stores: WAV, mono, 24-bit PCM, 46875 Hz (the pedal's native rate, 12 MHz / 256). Any audio program opens it. To convert:

ffmpeg -i myloop.wav -ar 48000 myloop-48k.wav      # 48 kHz
ffmpeg -i myloop.wav -b:a 320k myloop.mp3          # mp3

Upload

ap09 upload song.mp3

• Any format ffmpeg reads works. It is converted to mono, 24-bit, 46875 Hz; stereo is mixed down. A WAV already in that format is sent as is.
• Maximum about 10 minutes (650 blocks). The real limit is how many empty memory blocks the pedal has left, see ap09 space. If there are not enough, the upload stops before writing anything.
• The previous loop is not deleted: it stays in list, and select brings it back.
• Speed: about 1 s per second of audio.

Cut the file first, to the exact sample, for a loop that is precisely in time (times are seconds or m:ss.mmm):

ap09 upload song.wav --start 1:02.345 --end 1:10.345
ap09 upload song.wav --start 3.21 --length 8
ap09 upload song.wav --start 3.21 --bpm 120 --bars 4    # 4 bars of 4/4 = 8.000 s

--beats N changes the beats per bar (default 4).

Bring back, delete, clear

ap09 select 3       # loop #3 plays again (no audio is copied, only the index changes)
ap09 delete 2       # hide loop #2 from the list (asks first; -y to skip)
ap09 clear          # the pedal has no loop (asks first; -y to skip)
ap09 list --all     # deleted loops are still there, marked ✖; 'select' restores them

The pedal ignores the erase command over USB, so audio is never really wiped: delete only hides a loop, and it can be restored until its memory is reused.

Free space

$ ap09 space
free    162 blocks  ~151 s of audio
max     151 s per upload (pedal limit 10 min)
slots   29 free in the index (upload/select/clear use 1)

Debug commands

ap09 dump 1 0xF780000 0x60      # raw memory read: area, address, length
ap09 probe 11                   # raw command (hex) + optional hex body

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CLI and GUI are the same tool

Both use the functions in ap09.py. They share loop numbers, state names and icons, and the audio cache in ~/.cache/ap09/: a loop read by one is not read over USB again by the other.

	ap09	ap09-gui
device + current loop	info	"On the pedal" card, sidebar → Device
list loops	list	"Loops" list
show deleted loops	list --all	"deleted" switch
listen	play [-r N]	▶ buttons + player bar
save as WAV	download, download -a DIR	💾, sidebar → Download all
upload	upload FILE [--start --end --bpm --bars]	Upload / drag & drop, cut in the preview
make a loop play again	select N	↩ put on pedal
delete from the list	delete N	🗑
leave the pedal empty	clear	✖, sidebar → Clear
free space	space	sidebar → Memory → Scan

The pedal serves one program at a time: don't run ap09 while the app is working on it.

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Troubleshooting

message / symptom	fix
permission denied	install the udev rule (./install.sh, or see Manual install) and replug, or use sudo
looper 0416:5555 not found	check the cable (some are charge-only) and lsusb | grep 0416:5555
pedal busy	another ap09 or the app is using the pedal; wait for it to finish
not enough empty memory	fewer free blocks than the file needs; try a shorter file (see ap09 space)
loop index block is full	record any loop on the pedal once, so it compacts its index
the pedal still plays the old loop	unplug and replug it after every change
ap09: command not found	run pipx ensurepath and open a new terminal

Only the AP-09 (model 0x2715, "NANO LOOPER") has been tested. Other Rowin-made loopers with USB ID 0416:5555 (sold as Ammoon, Donner, FAME, Rowin, …) may use the same protocol with a different memory layout. Reports are welcome in the issues.

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How it works

In short: the pedal is a USB-MIDI device. Every command is a packet 00 59 | cmd | len | body | checksum, packed into 7-bit bytes and wrapped in a SysEx message F0 … F7. There are commands to read, write, erase and checksum the internal flash and a 256 MiB NAND. Loops are raw 24-bit PCM in 128 KiB NAND blocks, and a log of index records in block 1980 says which blocks make up each loop.

Full write-up — packet format, command table, NAND layout, index record, upload algorithm, open questions: docs/PROTOCOL.md.

Project layout

path
ap09.py	CLI and core library: transport, protocol, index, download, upload, select, clear, space
ap09_gui.py	GTK 4 / libadwaita app on top of ap09.py
install.sh	user install / uninstall (pipx, app menu entry, udev rule)
pyproject.toml	Python packaging: ap09 and ap09-gui entry points
data/	app icon, .desktop entry, udev rule
docs/	protocol notes, logo, screenshots

Lint: ruff check .

Credits

• Reiner Herrmann's loopertrx, where this started (issue #1).
• The reporter of loopertrx issue #6, for the first working SysEx message.

Author and license

wdog — wdog666@gmail.com

Released under the MIT License: you may use, copy, modify, improve and redistribute this software, provided that the copyright notice with the author's name (Copyright (c) 2026 wdog <wdog666@gmail.com>) and the license text are kept in all copies and derivative works.

Not affiliated with Ammoon or Rowin. The protocol was reverse-engineered for interoperability; use at your own risk.