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Documentation Index

Fetch the complete documentation index at: https://mintlify.com/gueritta/primemixxx/llms.txt

Use this file to discover all available pages before exploring further.

This page covers the most common issues encountered when deploying and running primemixxx on Denon Prime Go and Prime 4 hardware. Issues are grouped by symptom. For failed experiments and dead-end approaches, see Broken Experiments.

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Critical Pitfalls

Before diving into individual issues, review these ten critical rules. Violating any of them causes hard-to-diagnose failures:
  1. Never delete .midi.xml files — a missing mapping causes the MIXXX skin to render only a toolbar with no decks or library.
  2. Only lib/bin/mixxx works — mixxx.real crashes with an EGLFS error. bin/mixxx must symlink to ../lib/bin/mixxx.
  3. Mali DDK must be r1p0 — bundle’s libEGL.so/libGLESv2.so must symlink to the device’s native libmali.so.14.0, not the Buildroot r0p0 default.
  4. Bundle must NOT contain system libs — libc.so.6, libm.so.6, libpthread.so.0, libdl.so.2, librt.so.1, libstdc++.so.6, libgcc_s.so.1, ld-linux-armhf.so.3, libatomic.so.1 must come from the device’s /lib.
  5. Restart MIXXX correctly — systemctl restart mixxx-app.service silently fails. Use stop + restart engine.service.
  6. Don’t use print() in MIDI JS — it is silent on device. Use console.warn() or engine.log().
  7. WiFi drops after ~30s — use a keepalive ping or the USB Ethernet gadget at 192.168.42.1.
  8. Audio latency — use latency=5 in soundconfig.xml; latency=4 causes xruns.
  9. USB music library needs seeding — MIXXX won’t scan USB music unless the directories table in the SQLite DB has an entry.
  10. Repo is always source of truth — commit locally first, then deploy. Never edit files directly on the device without updating the repo.

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Connectivity

Check WiFi network: Ensure the development machine and Prime Go are on the same WiFi network. The device advertises via mDNS as primego.local.Use USB Ethernet gadget: Connect a USB-C cable between the device and computer. The device appears at the fixed address 192.168.42.1 — no network configuration required, no dropout risk.
ssh root@192.168.42.1   # password: denonprime4
WiFi keepalive: WiFi SSH sessions drop after ~30 seconds of silence. Run a keepalive ping in a separate terminal:
ping -i 25 <device-ip> > /dev/null &
Alternatively, install 99-wifi-power-save.rules via the device services installer — it permanently disables WiFi power save on the device.
Disable WiFi power save manually. This setting is not persistent across reboots:
iw dev wlan0 set power_save off
For a persistent fix, install the udev rule:
DEVICE_IP=<ip> ./scripts/dev-install-device-services.sh
This installs 99-wifi-power-save.rules, which runs iw dev wlan0 set power_save off automatically whenever wlan0 comes up.

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MIXXX Crashes

Segfaults on startup almost always indicate a library conflict. Check all three causes below before rebooting or reflashing.
Cause 1 — System libs in bundle: The bundle must NOT include these libraries — they must come from the device’s /lib:
  • libc.so.6
  • libm.so.6
  • libpthread.so.0
  • libdl.so.2
  • librt.so.1
  • libstdc++.so.6
  • libgcc_s.so.1
  • ld-linux-armhf.so.3
  • libatomic.so.1
Remove them from the bundle with scripts/dev-fix-device-libs.sh.Cause 2 — Mali DDK mismatch: See the dedicated accordion below.Cause 3 — Wrong binary: See the EGLFS crash accordion below.
The error message DDK is not compatible... r1p0 vs r0p0 means the bundled EGL/GLES libraries were built against Mali DDK r0p0 (Buildroot default), but the device’s kernel driver is r1p0. The fix is to symlink the bundle’s EGL libraries to the device’s native Mali library:
cd $BUNDLE/lib
rm -f libEGL.so libGLESv2.so libGLESv1_CM.so
ln -sf /usr/lib/libmali.so.14.0 libEGL.so
ln -sf /usr/lib/libmali.so.14.0 libGLESv2.so
ln -sf /usr/lib/libmali.so.14.0 libGLESv1_CM.so
Verify the GPU revision before debugging further:
cat /sys/devices/platform/ffa30000.gpu/gpuinfo
# expected: r1p0 0x0750
This crash occurs when using the wrong MIXXX binary. Buildroot produces two outputs:
BinarySizeWorks?
lib/bin/mixxx~10 MB (stripped)✅ Yes
mixxx.real~17 MB (unstripped)❌ No
bin/mixxx must be a symlink pointing to ../lib/bin/mixxx:
ls -la bin/mixxx
# Expected: bin/mixxx -> ../lib/bin/mixxx
# If it points to ../mixxx.real — fix it:
ln -sf ../lib/bin/mixxx bin/mixxx
The Prime 4 uses a DSI-1 display (not LVDS-1 like the Prime Go). MIXXX may segfault during EGL initialization due to DDK/DSI incompatibility with the native display.Use -platform offscreen to verify the binary itself is functional before troubleshooting the display:
/media/az01-internal/mixxx/lib/bin/mixxx -platform offscreen
If MIXXX runs without crashing in offscreen mode, the binary is healthy and the issue is display-specific. Native Prime 4 display support requires further investigation.

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MIXXX Service

If mixxx-app.service is masked, MIXXX will never start — not even after correct restarts.
Check the service state:
systemctl status mixxx-app.service
If the service is masked, unmask it:
systemctl unmask mixxx-app.service
Then follow the correct restart sequence below.
systemctl restart mixxx-app.service silently fails. The TKGL bootstrap script checks whether mixxx-app.service is already active and skips relaunch if so. The unit may appear active even if MIXXX has exited.
The only correct restart sequence is:
# 1. Stop the transient unit first
systemctl stop mixxx-app.service

# 2. Trigger TKGL to recreate it
systemctl restart engine.service
Do NOT use any of these — they will silently fail to restart MIXXX:
  • systemctl restart mixxx-app.service — TKGL sees the unit as running and skips
  • pkill mixxx + systemctl restart engine.service — orphaned unit stays “active”, TKGL skips
  • kill -9 <pid> — same problem as pkill

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Audio

At latency=4 the audio engine produces xruns (buffer underruns) on Prime Go hardware. Increase the latency setting in soundconfig.xml:
<latency>5</latency>
This is the minimum stable value on this hardware given the SCHED_FIFO priority setup and CPU shielding in place. Latency 4 is insufficient even with PREEMPT_RT.

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Music Library

MIXXX requires the directories table in the SQLite database to have at least one entry before it will scan for music. Check the current state:
sqlite3 /media/az01-internal/mixxx/settings/mixxxdb.sqlite \
  "SELECT directory FROM directories;"
If the output is empty, insert the music directory:
sqlite3 /media/az01-internal/mixxx/settings/mixxxdb.sqlite \
  "INSERT INTO directories (id, directory, volume) VALUES (1, '/media/az01-internal/mixxx/music', 1);"
Then restart MIXXX and trigger a library scan from the UI. The seed database (scripts/dev-collect-mixxx-bundle.sh) pre-populates this entry — if it is missing, the seed was not applied correctly.

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Skin and Display

This is caused by a missing MIDI mapping file. MIXXX skips controller initialization entirely when the mapping file cannot be found, and the skin renders only the top toolbar.
Check which mapping file mixxx.cfg references:
grep -A2 '\[ControllerPreset\]' /media/az01-internal/mixxx/settings/mixxx.cfg
Then verify the file exists at that path:
ls -la /media/az01-internal/mixxx/settings/controllers/Denon-Prime-Go.midi.xml
If it is missing, restore it from the mixxx-mapping/ directory in the bundle and restart MIXXX.

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MIDI Mapping Development

print() statements in MIDI mapping JavaScript are silently dropped on the device — output does not appear in logs or the terminal.Use these alternatives instead:
// Visible in MIXXX log output
console.warn("debug value:", myVar);

// Routed through MIXXX's engine logger
engine.log("debug value: " + myVar);
Both methods produce output that can be captured via journalctl -u mixxx-app.service -f.

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