fix(control)!: unify response frame format#20
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Add response packet format for both success and error cases, per-command response payloads, the framing recovery mechanism, and the undocumented I2C SetFrequency (0x10) command.
Add an explicit status code byte to all responses and make the length field mean total packet length, matching commands. 1) There was no way to distinguish a success response from an error response on the wire. The error code occupied the same position as the first data byte. For example, an I2C read returning 0x10 was indistinguishable from a Timeout error, or a red LED response (R=0xFF) from an error with message. 2) The length field had different semantics depending on whether the response was success or error. Success used payload-only length while error used total packet length. A host parser could not use the length to frame a read without first knowing the response type. Both are resolved by giving every response a status code at byte 3: 0x00 for success, existing codes for errors. BREAKING CHANGE: response format adds a status byte at offset 3
The previous commit changed the response frame format. Bump the firmware version so the host can distinguish protocol versions via bcdDevice.
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Add an explicit status code byte to all responses and make the length field mean total packet length, matching commands.
There was no way to distinguish a success response from an error response on the wire. The error code occupied the same position as the first data byte.
The length field had different semantics depending on whether the response was success or error. Success used payload-only length while error used total packet length.
Both are resolved by giving every response a status code at byte 3: 0x00 for success, existing codes for errors.
Bumps firmware version to v5.1.0 so the host can distinguish protocol versions via bcdDevice.
BREAKING CHANGE: response format adds a status byte at offset 3