# Printer Communication

## Summary

The printer communication system handles serial port connections to 3D printers, sending G-code commands, receiving responses, and managing print state. It uses a stream-based architecture for G-code processing with modular transformers for features like print leveling, pause handling, and temperature monitoring.

## Technical Description

### PrinterConnection Class

`PrinterConnection` is the main class managing printer communication:

**Communication States:**
| State | Description |
|-------|-------------|
| `Disconnected` | No active connection |
| `AttemptingToConnect` | Connection in progress |
| `FailedToConnect` | Connection attempt failed |
| `Connected` | Ready to receive commands |
| `PreparingToPrint` | Setting up for print |
| `Printing` | Active print from host |
| `PrintingFromSd` | Printing from SD card |
| `Paused` | Print paused |
| `FinishedPrint` | Print completed |
| `Disconnecting` | Closing connection |
| `ConnectionLost` | Unexpected disconnect |

**Supported Firmware:**
- Marlin
- Repetier
- Sprinter
- Smoothie

### Serial Communication

Connection parameters:
- `BaudRate` - Typically 115200 or 250000
- `SerialPort` - Platform-specific via `IFrostedSerialPort`
- Checksum support for error detection
- Line-by-line send/receive with buffering

**Response Parsing:**
```csharp
// Register callbacks for specific responses
readLineStartCallBacks.Register("ok", PrintingCanContinue);
readLineStartCallBacks.Register("T:", ReadTemperatures);
readLineStartCallBacks.Register("Error:", PrinterReportsError);
```

**Write Callbacks:**
```csharp
writeLineStartCallBacks.Register("M104", HotendTemperatureWasWritenToPrinter);
writeLineStartCallBacks.Register("M140", BedTemperatureWasWritenToPrinter);
```

### G-Code Stream Pipeline

G-code is processed through a chain of `GCodeStream` transformers:

```
GCodeFileStream (source)
└── GCodeSwitcher (file switching)
    └── QueuedCommandsStream (injected commands)
        └── PauseHandlingStream (pause/resume)
            └── RelativeToAbsoluteStream (coordinate conversion)
                └── PrintLevelingStream (bed leveling adjustments)
                    └── BabyStepsStream (live Z offset)
                        └── MaxLengthStream (segment splitting)
                            └── ToolChangeStream (extruder switching)
                                └── ExtrusionMultiplierStream
                                    └── FeedRateMultiplierStream
                                        └── WaitForTempStream
                                            └── RequestTemperaturesStream
                                                └── to Serial Port
```

Each stream can:
- Modify G-code lines passing through
- Inject additional commands
- Block/delay commands
- Monitor state

### Key G-Code Streams

| Stream | Purpose |
|--------|---------|
| `GCodeFileStream` | Reads G-code from file |
| `GCodeSwitcher` | Switches between print files |
| `QueuedCommandsStream` | Injects immediate commands |
| `PauseHandlingStream` | Manages pause/resume logic |
| `PrintLevelingStream` | Applies bed leveling corrections |
| `MaxLengthStream` | Splits long moves into segments |
| `ToolChangeStream` | Handles multi-extruder switching |
| `WaitForTempStream` | Waits for temperature targets |
| `PrintRecoveryStream` | Enables print recovery after failure |
| `ValidatePrintLevelingStream` | Validates leveling data |
| `SoftwareEndstopsStream` | Enforces software limits |
| `BabyStepsStream` | Applies live Z offset adjustments |

### Temperature Management

Temperature tracking for:
- Heated bed (`ActualBedTemperature`, `TargetBedTemperature`)
- Up to 16 hotends (`actualHotendTemperature[]`, `targetHotendTemperature[]`)

**Temperature Reading:**
```csharp
// Parses responses like "T:205.3 /210.0 B:60.0 /60.0"
readLineContainsCallBacks.Register("T:", ReadTemperatures);
```

**Automatic Heater Shutdown:**
- `TimeToHoldTemperature` - Configurable delay
- `SecondsToHoldTemperature` - Countdown timer
- `TurnOffBedAndExtruders(TurnOff.AfterDelay)` - Scheduled shutdown

### Print State Management

**Detailed Printing States:**
| State | Description |
|-------|-------------|
| `HomingAxis` | Executing homing sequence |
| `HeatingBed` | Waiting for bed temperature |
| `HeatingT0` | Waiting for extruder 0 temp |
| `HeatingT1` | Waiting for extruder 1 temp |
| `Printing` | Active G-code execution |

**Events:**
| Event | Description |
|-------|-------------|
| `PrintStarted` | Print begins |
| `PrintFinished` | Print completes |
| `CancelRequested` | Cancel initiated |
| `CancelCompleted` | Cancel finished |
| `PauseOnLayer` | Pause at specific layer |
| `FilamentRunout` | Filament sensor triggered |

### Error Handling

Error detection via response parsing:
```csharp
readLineContainsCallBacks.Register("MINTEMP", PrinterReportsError);
readLineContainsCallBacks.Register("MAXTEMP", PrinterReportsError);
readLineContainsCallBacks.Register("Thermal Runaway", PrinterReportsError);
```

Errors trigger:
1. `ErrorReported` event
2. Print pause (if printing)
3. User notification dialog

### Alternative Drivers

The system supports alternative communication protocols:

| Driver | Location | Purpose |
|--------|----------|---------|
| Emulator | Drivers/Emulator | Virtual printer for testing |
| TCPIP | Drivers/TCPIP | Network-connected printers |
| X3G | Drivers/X3G | MakerBot X3G protocol |

### TerminalLog

All communication is logged via `TerminalLog`:
- Send/receive history
- Exportable for debugging
- Real-time display in UI terminal

### Design Rationale

**Stream Pipeline**: The chain-of-responsibility pattern allows:
- Modular feature implementation
- Easy addition/removal of processing stages
- Clear data flow through transformations
- Independent testing of each stage

**Callback-Based Parsing**: Using `StartsWith` and `Contains` callbacks:
- Efficient string matching
- Handles firmware variations
- Easy to extend for new responses

**State Machine**: The `CommunicationStates` enum ensures:
- Clear state transitions
- Appropriate UI updates
- Safe operation sequencing

## Reference

### Core Classes

| Class | Location | Description |
|-------|----------|-------------|
| `PrinterConnection` | [PrinterCommunication/PrinterConnection.cs](MatterControlLib/PrinterCommunication/PrinterConnection.cs) | Main communication class |
| `TerminalLog` | [PrinterCommunication/TerminalLog.cs](MatterControlLib/PrinterCommunication/TerminalLog.cs) | Communication log |
| `PrinterConfig` | [SlicerConfiguration/PrinterConfig.cs](MatterControlLib/SlicerConfiguration/Settings/PrinterConfig.cs) | Printer configuration |

### G-Code Streams

| Class | Location | Description |
|-------|----------|-------------|
| `GCodeStream` | [PrinterCommunication/Io/GCodeStream.cs](MatterControlLib/PrinterCommunication/Io/GCodeStream.cs) | Base stream class |
| `GCodeSwitcher` | [PrinterCommunication/Io/GCodeSwitcher.cs](MatterControlLib/PrinterCommunication/Io/GCodeSwitcher.cs) | File switching |
| `PauseHandlingStream` | [PrinterCommunication/Io/PauseHandlingStream.cs](MatterControlLib/PrinterCommunication/Io/PauseHandlingStream.cs) | Pause/resume |
| `PrintLevelingStream` | [PrinterCommunication/Io/PrintLevelingStream.cs](MatterControlLib/PrinterCommunication/Io/PrintLevelingStream.cs) | Bed leveling |
| `ToolChangeStream` | [PrinterCommunication/Io/ToolChangeStream.cs](MatterControlLib/PrinterCommunication/Io/ToolChangeStream.cs) | Tool changes |
| `WaitForTempStream` | [PrinterCommunication/Io/WaitForTempStream.cs](MatterControlLib/PrinterCommunication/Io/WaitForTempStream.cs) | Temperature wait |

### Events

| Event | Source | Description |
|-------|--------|-------------|
| `CommunicationStateChanged` | `PrinterConnection` | State transition |
| `TemperatureRead` | `PrinterConnection` | Temp update |
| `LineReceived` | `PrinterConnection` | Serial input |
| `LineSent` | `PrinterConnection` | Serial output |
| `PrintFinished` | `PrinterConnection` | Print complete |
| `ErrorReported` | `PrinterConnection` | Printer error |

### Enums

| Enum | Values |
|------|--------|
| `CommunicationStates` | Disconnected, Connected, Printing, Paused, etc. |
| `DetailedPrintingState` | HomingAxis, HeatingBed, HeatingT0, Printing |
| `FirmwareTypes` | Unknown, Repetier, Marlin, Sprinter, Smoothie |
| `TurnOff` | Now, AfterDelay |
| `Axis` | X, Y, Z, E, XYZ, C |