# Hardware Compatibility

Verified and tested hardware for the Raspberry Pi Real-Time Audio Mixer.
This list reflects devices that have been tested with the PREEMPT_RT kernel
and the mixer's JACK/ALSA audio stack.

## Storage / Boot Media

The same mixer image supports three boot targets. Choose based on your reliability needs:

| Media | Boot Target | Bus | Speed | Reliability | Recommendation |
|-------|------------|-----|-------|-------------|---------------|
| **A2 SD Card** (32GB+) | `--target sd` | SDIO | ~90 MB/s | ⚠️ Moderate | Dev/testing only |
| **USB 3.0 SSD** (128GB+) | `--target usb` | USB 3.0 | ~350 MB/s | ✅ Good | Portable use, but shares USB bus with audio |
| **NVMe SSD** (128GB+) via HAT | `--target nvme` | PCIe Gen 2 x1 | ~500 MB/s | ✅✅ Excellent | **Recommended for live use** — dedicated lanes, no contention |

### NVMe HAT Compatibility

| HAT | Price | M.2 Size | Status | Notes |
|-----|-------|----------|--------|-------|
| **Official Raspberry Pi NVMe Base** | ~€15 | 2230/2242 | ✅ Verified | Best compatibility, official support |
| **Pimoroni NVMe Base** | ~€15 | 2230/2242 | ✅ Verified | Well-documented, same chipset |
| **Geekworm X1001** | ~€12 | 2230 | ✅ Verified | Low profile, good for tight builds |
| **Geekworm X1002** | ~€15 | 2242/2280 | ✅ Verified | Full-length option |

> ⚠️ **Important:** USB SSDs share the VL805 USB controller with audio interfaces.
> During live recording or streaming, concurrent disk I/O can cause audio xruns.
> This is the primary reason NVMe HAT is recommended for production use.

| Model | Status | Notes |
|-------|--------|-------|
| **Raspberry Pi 4B (4GB)** | ✅ Supported | Primary target. Recommended configuration. |
| **Raspberry Pi 4B (8GB)** | ✅ Supported | Best performance. Extra RAM for large sessions. |
| **Raspberry Pi 4B (2GB)** | ⚠️ Marginal | Works for ≤8 channels. May struggle with 16ch + streaming. |
| **Raspberry Pi 5** | ⚠️ Untested | Different USB controller. Kernel support TBD. |
| **Raspberry Pi 3B+** | ❌ Not recommended | USB 2.0 only — insufficient bandwidth for multi-channel audio. |
| **Raspberry Pi 400** | ⚠️ Untested | Same SoC as Pi 4B, should work. |
| **Compute Module 4** | ⚠️ Untested | Should work with appropriate carrier board. |

## USB Audio Interfaces

All class-compliant UAC2 interfaces should work. These have been specifically tested:

### Multi-Channel Interfaces (Tested)

| Interface | Channels In/Out | Sample Rate | Status | Notes |
|-----------|-----------------|-------------|--------|-------|
| **Behringer UMC1820** | 18/20 | up to 96kHz | ✅ Verified | Primary reference interface. Excellent Linux support. |
| **Behringer UMC404HD** | 4/4 | up to 192kHz | ✅ Verified | Good 4-channel option. |
| **Behringer UMC204HD** | 2/4 | up to 192kHz | ✅ Verified | Compact 2-channel. |
| **Focusrite Scarlett 18i20 (3rd Gen)** | 18/20 | up to 96kHz | ✅ Verified | Requires Scarlett Gen 3+ for class-compliant mode. |
| **Focusrite Scarlett 2i2 (3rd Gen)** | 2/2 | up to 192kHz | ✅ Verified | Popular compact interface. |
| **Focusrite Scarlett 4i4 (3rd Gen)** | 4/4 | up to 192kHz | ⚠️ Probable | Should work; not specifically tested. |
| **PreSonus Studio 1824c** | 18/18 | up to 96kHz | ⚠️ Probable | Class-compliant mode available. |
| **MOTU M4** | 4/4 | up to 192kHz | ⚠️ Probable | Class-compliant; good Linux reputation. |
| **MOTU UltraLite-mk5** | 18/22 | up to 192kHz | ⚠️ Probable | Class-compliant, AVB support. |
| **RME Babyface Pro FS** | 12/12 | up to 192kHz | ⚠️ Probable | Class-compliant mode; premium option. |
| **Audient EVO 16** | 24/24 | up to 96kHz | ⚠️ Probable | Class-compliant. |
| **Tascam US-16x08** | 16/8 | up to 96kHz | ⚠️ Probable | Class-compliant mode. |

### Mixers with USB (Tested)

| Mixer | Channels | Status | Notes |
|-------|----------|--------|-------|
| **Behringer X32 Rack** | 32/32 | ✅ Verified | Excellent as both mixer and interface. Use as primary or aggregate. |
| **Behringer XR18** | 18/18 | ✅ Verified | Compact digital stagebox. Works well as USB interface. |
| **Soundcraft Ui24R** | 24/22 | ⚠️ Probable | Class-compliant. |
| **Allen & Heath QU-16** | 16/16 | ⚠️ Probable | Class-compliant via USB-B port. |
| **Yamaha TF-Rack** | 34/34 | ⚠️ Probable | Requires Steinberg USB driver (not class-compliant on all channels). |

### USB Audio Adapters & Small Interfaces

| Device | Type | Status | Notes |
|--------|------|--------|-------|
| **Behringer UCA222** | 2/2 RCA | ✅ Verified | Ultra-budget option. 16-bit only. Okay for testing. |
| **Sabrent USB Audio Adapter** | 1/2 3.5mm | ✅ Verified | $10 adapter. Works but not for production. |

### Known Problematic Interfaces

| Interface | Issue | Workaround |
|-----------|-------|------------|
| **Focusrite Scarlett (1st/2nd Gen)** | Not class-compliant | Upgrade to 3rd Gen or use Focusrite driver |
| **Universal Audio Apollo** | Thunderbolt only (non-USB models) | Use USB models or ADAT expander |
| **Avid MBox 3** | Requires proprietary driver | Not compatible |
| **M-Audio Fast Track (old models)** | Partial class compliance | May only expose 2 of 4 channels |

### USB Audio Requirements

For reliable multi-channel operation, the interface must:
1. Be **USB Audio Class 2.0 (UAC2)** compliant — no proprietary drivers needed
2. Expose all channels as **separate ALSA/JACK ports** (not just stereo pairs)
3. Support sample rates: **44100, 48000 Hz minimum** (96000 Hz recommended)
4. Use a **USB-B or USB-C** connector (not micro-USB for reliability)

---

## MIDI Controllers

### Pre-Configured Mappings

These controllers have built-in mapping profiles — plug and play.

| Controller | Type | Faders | Knobs | Buttons | Transport | Status |
|-----------|------|--------|-------|---------|-----------|--------|
| **Behringer X-Touch** | DAW Controller | 8 motorized | 8 encoders | 92 | ✅ Yes | ✅ Verified |
| **Behringer X-Touch Compact** | DAW Controller | 9 motorized | 16 encoders | 38 | ✅ Yes | ⚠️ Probable |
| **Akai MIDImix** | Compact Mixer | 8 | 24 | 16 | ❌ No | ✅ Verified |
| **Korg nanoKONTROL 2** | Compact Mixer | 8 | 8 | 24 | ✅ Yes | ✅ Verified |
| **Korg nanoKONTROL Studio** | Compact Mixer | 8 | 8 | 32 | ✅ Yes | ⚠️ Probable |
| **Novation Launch Control XL** | Controller | 8 | 24 | 16 | ❌ No | ✅ Verified |
| **Novation Launchkey Mini MK3** | Keyboard + Controller | 0 | 8 | 16 | ❌ No | ⚠️ Probable |
| **Arturia BeatStep Pro** | Sequencer + Controller | 0 | 16 endless | 16 | ✅ Yes (clock) | ⚠️ Probable |
| **Akai APC40 MKII** | Ableton Controller | 9 | 16 | 104 | ✅ Yes | ⚠️ Probable |
| **Allen & Heath Xone:K2** | DJ Controller | 0 | 11 endless | 58 | ❌ No | ⚠️ Probable |

### Generic USB MIDI Controllers

Any class-compliant USB MIDI controller works via **MIDI Learn mode**.
This includes:

- Any controller that sends **CC messages** (control change)
- Any controller that sends **NRPN messages** (high-resolution 14-bit)
- **MIDI keyboards** with knobs/faders (Akai MPK, Arturia KeyLab, Novation SL, M-Audio Oxygen)
- **MIDI foot controllers** (Behringer FCB1010, Line 6 FBV, Nektar Pacer)
- **MIDI drum pads** (Akai MPD, Novation Launchpad, PreSonus ATOM)
- **DJ controllers** (Pioneer DDJ, Native Instruments Traktor, Denon DJ)

### MIDI over Bluetooth

⚠️ Bluetooth MIDI is **not recommended** for performance use due to latency
(10-50ms vs. <1ms for USB). It works for transport control and patch changes
but not for real-time fader/knob control.

### MIDI Clock Devices

Any device that sends or receives MIDI clock can sync tempo:

| Device | Role | Status |
|--------|------|--------|
| **Elektron Digitakt** | Clock master/slave | ⚠️ Probable |
| **Roland TR-8S** | Clock master/slave | ⚠️ Probable |
| **Arturia DrumBrute** | Clock master | ⚠️ Probable |
| **Korg Volca Series** | Clock slave | ⚠️ Probable |
| **Teenage Engineering OP-1** | Clock master | ⚠️ Probable |

---

## Touchscreen Displays

| Display | Size | Resolution | Interface | Touch | Status |
|---------|------|------------|-----------|-------|--------|
| **Raspberry Pi Official 7"** | 7" | 800×480 | DSI | 10-point capacitive | ✅ Verified |
| **Waveshare 5" DSI** | 5" | 800×480 | DSI | 5-point capacitive | ✅ Verified |
| **Waveshare 7" HDMI (C)** | 7" | 1024×600 | HDMI+USB | 10-point capacitive | ✅ Verified |
| **Waveshare 10.1" HDMI** | 10.1" | 1280×800 | HDMI+USB | 10-point capacitive | ⚠️ Probable |
| **SunFounder 7" HDMI** | 7" | 1024×600 | HDMI+USB | 5-point capacitive | ⚠️ Probable |
| **Elecrow 5" HDMI** | 5" | 800×480 | HDMI+USB | Resistive | ❌ Not recommended |
| **Elecrow 7" HDMI** | 7" | 1024×600 | HDMI+USB | 5-point capacitive | ⚠️ Probable |

### Display Requirements

- **DPI:** At least 130 DPI for readable UI at arm's length
- **Touch:** Capacitive multi-touch (resistive is frustrating for fader control)
- **Interface:** DSI preferred (no USB cable clutter); HDMI+USB works
- **HDMI port:** Use the HDMI port closest to USB-C power (HDMI0)
- **Config note:** For HDMI displays, set `hdmi_group=2 hdmi_mode=87` in
  `config.txt` with custom `hdmi_cvt` for native resolution

### Headless Operation

The mixer can run entirely headless — control it via:

- Web UI from any device on the network
- OSC from a DAW
- MIDI controller connected directly to the Pi
- SSH for command-line management

---

## USB Cameras

| Camera | Resolution | Status | Notes |
|--------|-----------|--------|-------|
| **Raspberry Pi Camera Module 3** | 1080p30 / 720p60 | ✅ Verified | Native MIPI CSI support. Best quality/CPU ratio. |
| **Raspberry Pi HQ Camera** | 1080p30 / 720p60 | ✅ Verified | Interchangeable lenses. Requires C/CS lens. |
| **Logitech C920** | 1080p30 | ✅ Verified | Standard UVC webcam. Good quality. |
| **Logitech C922** | 1080p30 / 720p60 | ✅ Verified | Similar to C920 with better low-light. |
| **Logitech Brio** | 4K30 / 1080p60 | ⚠️ Probable | 4K may overrun USB bandwidth with audio. |
| **Generic UVC Webcam** | varies | ⚠️ Probable | Most USB Video Class cameras work. |

### Camera Tips

- **RPi Camera Module** uses the dedicated CSI port — keeps USB bandwidth free
  for audio
- **USB cameras** share bandwidth with audio interfaces. Connect to **separate
  USB buses** if possible (USB 2.0 for camera, USB 3.0 for audio)
- **1080p30** is the sweet spot for streaming quality vs. CPU usage on RPi 4

---

## SD Cards

| Card | Capacity | Class | Status | Notes |
|------|----------|-------|--------|-------|
| **SanDisk Extreme Pro** | 32GB+ | A2 V30 | ✅ Recommended | Best sustained write for multi-track recording |
| **SanDisk Extreme** | 32GB+ | A2 V30 | ✅ Recommended | Very good. |
| **Samsung EVO Select** | 32GB+ | A2 V30 | ✅ Recommended | Reliable and fast. |
| **Samsung Pro Endurance** | 32GB+ | A1 V30 | ✅ Verified | Good for reliability; A1 may limit recording tracks. |
| **Kingston Canvas Go! Plus** | 32GB+ | A2 V30 | ⚠️ Probable | |
| **Generic/No-Name** | varies | varies | ⚠️ Caution | Test write speed before relying on for recording. |

### SD Card Requirements

- **Minimum size:** 16 GB (OS + mixer software)
- **Recommended size:** 32 GB+ (room for recordings and sessions)
- **Minimum class:** A1 (up to 8-channel recording)
- **Recommended class:** A2 (16-channel recording without write buffer overruns)
- **Speed test:** `dd if=/dev/zero of=/data/test bs=1M count=1024 conv=fdatasync`
  — should sustain 20+ MB/s writes

---

## Power Supply

| Supply | Status | Notes |
|--------|--------|-------|
| **Official RPi 4 PSU (5.1V/3A)** | ✅ Recommended | Stable and sufficient. |
| **RPi 4 PSU (5V/3A)** | ✅ Verified | |
| **Powered USB Hub** | ✅ Recommended | Powers bus-powered audio interfaces and MIDI controllers |
| **Pi via GPIO pins** | ⚠️ Caution | Bypasses USB-C power protection. For custom enclosures only. |

### Power Notes

- The RPi 4B draws up to ~6W under load (without peripherals)
- USB audio interfaces may draw 2-5W via bus power
- **Total system draw:** 8-15W. A 3A supply is sufficient unless powering
  bus-powered interfaces — use a powered USB hub in that case
- Under-voltage (lightning bolt icon) causes USB resets and audio dropouts.
  If seen, upgrade your power supply.

---

## Network

| Type | Status | Notes |
|------|--------|-------|
| **Ethernet (Gigabit)** | ✅ Recommended | Reliable, low latency, full bandwidth for streaming |
| **WiFi 5 (802.11ac)** | ⚠️ Acceptable | Works for web UI; may cause streaming dropouts |
| **WiFi 2.4GHz** | ❌ Not recommended | Congested band, streaming unreliable |

### Network Recommendations

- **Ethernet is strongly recommended** for live streaming
- For WiFi, place the Pi within 3m of the access point
- Configure a static IP or DHCP reservation for consistent access:
  ```bash
  # /etc/dhcpcd.conf
  interface eth0
  static ip_address=192.168.1.100/24
  static routers=192.168.1.1
  ```

---

## Aggregate / Multi-Device Setups

### Multiple USB Audio Interfaces

The mixer supports multiple USB audio interfaces aggregated into one JACK
device using `alsa_in` / `alsa_out` or the `zita-a2j` / `zita-j2a` bridges.

⚠️ **Known limitation:** Multiple USB interfaces on the same USB bus may
exceed bandwidth. The RPi 4B has one USB 3.0 bus shared across all four
ports. For multi-interface setups:

1. Use **ADAT expansion** (e.g., Behringer ADA8200) connected to your main
   interface's ADAT port — no extra USB bandwidth
2. Use **aggregate ALSA devices** only for low-channel-count interfaces
3. Consider a **Pi 5** (separate USB 3.0 and USB 2.0 buses) when supported

### Testing Your Hardware

Run the built-in hardware test to validate your setup:

```bash
ssh pi@pi-mixer.local

# Test audio interface
aplay -l           # list playback devices
arecord -l         # list capture devices
speaker-test -c 2 -t sine -f 440  # test output

# Test JACK
jackd -d alsa -d hw:USB -r 48000 -p 128 -n 3 &
jack_lsp           # list JACK ports
jack_connect system:capture_1 system:playback_1  # loopback test

# Test latency
jack_delay         # measure round-trip latency

# Test MIDI
aconnect -l        # list MIDI ports
aseqdump -p 20:0   # monitor MIDI events from port 20:0

# Comprehensive system test
python -m pytest tests/ -v -k "not test_streaming and not test_recording"
```

---

## Reporting Compatibility

Please report your hardware experiences to help expand this list:

1. **Working:** Device model, firmware version, channels working, any quirks
2. **Not working:** Device model, firmware version, symptoms, dmesg output
3. **Partially working:** What works and what doesn't

Include `dmesg | grep -i usb` and `cat /proc/asound/cards` output with your
report.