The Big OneBelow is the initial design document for the serial protocol (see protocol.txt for the latest version, as this will likely change over time).
Protocol Info
Message Structure (bi-directional):
| Segment | Length |
| Frame Start | 1 byte (0x7e) |
| Length | 1 byte |
| Command | 1 byte |
| Payload | 0 - 254 bytes |
| Checksum | 1 byte |
Commands:
There are four logical message types:
- 1) PC initiates a message to Stubby
- 2) Stubby responds to a message from PC
- 3) Stubby initiates a message to PC
- 4) PC responds to a message from Stubby
Message types 1 and 2 comprise the majority of communication. Message types 3 and 4 imply an event-driven programming model. Initially, we do not want to do this as it adds complexity to the new programmer, however we do not want to preclude this from being added at a later date.
Commands have a variable payload. A description of payloads is below. Portions in [square brackets] are optional.
| Command | Direction | Payload |
| SendAcknowledge | Stubby -> PC | Command being ack'd (1 byte) |
| SendComplete | Stubby -> PC | Command completed (1 byte) |
| RequestMove | PC -> Stubby | Distance (2 btyes), Angle (4 bytes), [Speed (1 byte)] |
| RequestTurn | PC -> Stubby | Angle (4 bytes), [Speed (1 byte)] |
| RequestTranslate | PC -> Stubby | Axis (1 byte), Distance (1 byte) |
| RequestRotate | PC -> Stubby | Axis (1 byte), Angle (4 bytes) |
| RequestDistance | PC -> Stubby | Null |
| SendDistance | Stubby -> PC | Distance (2 bytes) |
| RequestOptical | PC -> Stubby | Null |
| SendOptical | Stubby -> PC | 1 byte / sensor (TODO: How many sensors?) |
| RequestBattery | PC -> Stubby | Null |
| SendBattery | Stubby -> PC | 1 byte |
| RequestDebug | PC -> Stubby | Null |
| SendDebug | Stubby -> PC | Variable depending on message, max 254 bytes |
| RequestSetLED | PC -> Stubby | 3 bytes (RGB Value) |
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