# KVM Switch: Mac ↔ Nobara

Software KVM to switch Dell U3821DW monitor and Logitech MX peripherals between Mac and Nobara.

## Hardware

- **Monitor:** Dell U3821DW (USB-C to Mac, HDMI 2 to Nobara)
- **Keyboard:** Logitech MX Keys S
- **Mouse:** Logitech MX Master 3S
- **Bolt #1:** Connected directly to Nobara
- **Bolt #2:** Connected to Dell monitor USB hub (routes to Mac via USB-C)

## Channel Setup

| Channel | Code | Connection | Computer |
|---------|------|------------|----------|
| 2 | 0x01 | Bolt #1 | Nobara |
| 3 | 0x02 | Bolt #2 (via monitor) | Mac |

## Mac Setup

### Prerequisites
```bash
# Install m1ddc (DDC control for Apple Silicon)
brew install m1ddc

# Install hidapitester
curl -sL https://github.com/todbot/hidapitester/releases/latest/download/hidapitester-macos-arm64.zip -o /tmp/hidapitester.zip
unzip -o /tmp/hidapitester.zip -d ~/bin/
chmod +x ~/bin/hidapitester
```

### Install Script
```bash
mkdir -p ~/scripts
cp to_nobara.sh ~/scripts/
chmod +x ~/scripts/to_nobara.sh
```

### Keyboard Shortcut (Logi Options+)
1. Logi Options+ → MX Keys S → Smart Actions
2. Create action triggered by F12
3. Action: Open File → ~/scripts/to_nobara.sh

## Nobara Setup

### Prerequisites
```bash
# Install ddcutil
sudo dnf install -y ddcutil

# Add user to i2c group (REBOOT REQUIRED)
sudo usermod -aG i2c $USER

# Install hidapitester
mkdir -p ~/bin
curl -sL https://github.com/todbot/hidapitester/releases/latest/download/hidapitester-linux-amd64.zip -o /tmp/hidapitester.zip
unzip -o /tmp/hidapitester.zip -d ~/bin/
chmod +x ~/bin/hidapitester
rm /tmp/hidapitester.zip

# Udev rule for non-root HID access
echo 'SUBSYSTEM=="usb", ATTRS{idVendor}=="046d", ATTRS{idProduct}=="c548", MODE="0666"' | \
  sudo tee /etc/udev/rules.d/99-logitech-bolt.rules
sudo udevadm control --reload-rules && sudo udevadm trigger
```

### Install Script
```bash
mkdir -p ~/scripts
cp to_mac.sh ~/scripts/
chmod +x ~/scripts/to_mac.sh
```

### Keyboard Shortcut (GNOME)
1. Settings → Keyboard → Custom Shortcuts
2. Add shortcut:
   - Name: KVM to Mac
   - Command: /home/USER/scripts/to_mac.sh
   - Shortcut: F12

## Pairing Peripherals

Each device must be paired to BOTH Bolt receivers:

### MX Master 3S / MX Keys S
1. Press Easy-Switch button to select channel (2 for Nobara, 3 for Mac)
2. Hold 3 seconds until LED blinks fast
3. Use Logi Options+ (Mac) or Solaar (Linux) to complete pairing

### Install Solaar (Linux)
```bash
sudo dnf install solaar
solaar &
# Click "Pair new device" while peripheral is blinking
```

## Troubleshooting

### Monitor doesn't switch
- Check DDC/CI is enabled: Monitor Menu → Others → DDC/CI → On
- Mac: Ensure USB-C cable supports data (not video-only)
- Linux: Ensure user is in i2c group and rebooted

### Peripherals don't switch
- Verify devices are paired to both Bolt receivers
- Check device indices with: `solaar show` (Linux)
- Device indices (0x01, 0x02) depend on pairing order

### Find correct device indices
```bash
# On Linux with solaar
solaar show

# Or query via HID++
hidapitester --vidpid 046d/c548 --list-detail
```

## DDC Input Codes (Dell U3821DW)

| Input | Code |
|-------|------|
| HDMI 1 | 17 |
| HDMI 2 | 18 |
| USB-C | 27 |
| DP 1 | 15 |
| DP 2 | 16 |