MSI MPG 491CQP Control

USB HID control for MSI MPG 491CQP monitor. Rust implementation.

Project Structure

crates/
├── msi-core/       # Core library (protocol, features, monitor API)
├── msi-cli/        # Command-line interface
├── msi-gui/        # Desktop GUI (Dioxus)
└── msi-hwtest/     # Hardware integration tests

docs/
├── protocol/       # Protocol specifications (source of truth)
├── guides/         # User guides
└── research/       # Research notes and data

Before Making Changes

Run
```
cargo test
```
to verify tests pass
Read the relevant AGENTS.md in subdirectories (
```
crates/AGENTS.md
```
,
```
docs/AGENTS.md
```
)

After Making Changes

Run
```
cargo fmt
```
(no approval needed)
Run
```
cargo clippy
```
and fix warnings
Run
```
cargo test
```
to verify nothing broke
For protocol changes, update
```
docs/protocol/usb-hid-reference.md
```

Always Do

Commit changes after each logical step (don't wait to be reminded)
When you discover a missing rule, add it to AGENTS.md
Use Report ID
```
0x01
```
in all USB HID commands (0x00 fails silently)
Encode feature codes as 5 ASCII characters (
```
0x0400
```
→
```
"00400"
```
)
Use 3-digit decimal values for most features (
```
75
```
→
```
"075"
```
)
Document protocol discoveries in
```
docs/protocol/
```

Never Do

Use Report ID
```
0x00
```
(fails silently, no error returned)
Commit binary files (pcap captures, firmware, etc.)
Guess at protocol details without verification from captures
Test unknown feature codes without asking (could have side effects)

Ask First

Testing unknown feature codes on hardware
Adding new dependencies to Cargo.toml
Major architectural changes

Quick Commands

cargo build --release           # Build all
cargo test                # Unit tests
cargo run --bin msi-cli -- list # Test CLI
cargo clippy                    # Lint
just check                      # Full check (requires just)

Hardware Setup

Linux: Install udev rules:

sudo cp config/udev/99-msi-monitor.rules /etc/udev/rules.d/

macOS: No setup required
Windows: HID driver usually automatic

crates/
├── msi-core/       # Core library (protocol, features, monitor API)
├── msi-cli/        # Command-line interface
├── msi-gui/        # Desktop GUI (Dioxus)
└── msi-hwtest/     # Hardware integration tests

docs/
├── protocol/       # Protocol specifications (source of truth)
├── guides/         # User guides
└── research/       # Research notes and data

Always Do

Commit changes after each logical step (don't wait to be reminded)

When you discover a missing rule, add it to AGENTS.md

Use Report ID

0x01

in all USB HID commands (0x00 fails silently)

Encode feature codes as 5 ASCII characters (

0x0400

→

"00400"

)

Use 3-digit decimal values for most features (

→

"075"

)

Document protocol discoveries in

docs/protocol/

cargo build --release           # Build all
cargo test                # Unit tests
cargo run --bin msi-cli -- list # Test CLI
cargo clippy                    # Lint
just check                      # Full check (requires just)

MSI MPG 491CQP Control

MSI MPG 491CQP Control

Project Structure

Before Making Changes

After Making Changes

Always Do

Never Do

Ask First

Quick Commands

Hardware Setup

See Also

Related Skills

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MSI MPG 491CQP Control

Project Structure

Before Making Changes

After Making Changes

Always Do

Never Do

Ask First

Quick Commands

Hardware Setup

See Also