Camera Feedback, the 4th

Once again the discussion of how to get camera feedback on Hermes Flight 3 reared it's head, this time because of a remarkable discovery by Dennis G. Dennis discovered UART connections to the camera microcontroller allow for detailed insight into the camera's status.

This was incredibly exciting, as it was discovered that the SATA cable has 2 UART lines on it already, which would be enough for camera feedback from the two radial facing cameras in the avionics bay.

A brief discussion was held about the reliability of the UART feedback vs Photodiode feedback. There was no consensus. Filtering and detecting camera starts from the photodiode may be difficult. Dennis brought up concerns about inconsistent light patterns, but Charlie suspects that this is a function of how the camera is used (i.e. charging lights won't override recording lights) but testing would be needed to determine this conclusively. James had concerns about the reliability of human legible UART outputs, and how much parsing would need to happen to get useable data from them.

There was discussion of UART Muxing, which I don't understand, it might let us talk to all cameras, it might be hard for Pyxida to interpret. Someone more Course 6 than me please chime in.

Dennis thinks we can command the cameras via UART. If this is the case, the BBC can be eliminated entirely. It is unclear if this is possible. James notes that the 2 UART lines may be TX/RX so if we need both for Pyxida RX, we may not be able to command and receive from two cameras.

Unfortunately, the UART pins are buried on pads surrounded by components, so connecting to them reliably will not be straightforward. Dennis says there are two unused pins on the weird 10 pin USB, so we could solder thin wires from the UART pads to the USB, then use a camera breakout board to pull those two wire to a SATA breakout for the UART. We'd have mechanical concerns if we just run wires straight to those pads.

A separate but related discussion indicted the surface mount soldering of the battery leads. It has been proposed to replace the leads with a locking surface mount JST connector.

It is hoped that the cameras can also report diagnostic data like battery voltage and processor temperature which Pyxida could report to the ground station. This is a stretch goal. The only critical functionality is confirming that the camera is on and recording.