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So turns out the pads on the microbit are actually only active on the "front" (LED side) of the uBit. So, I can't use top and bottom rows...I have to use the top two. :( Means when we get to soldering, we may want to clip off the bottom two rows to make it easier.
Next snafu: pins have multiple roles...so, for example, if you want to use P3, you have to turn off the LED. See https://makecode.microbit.org/device/pins for details. But, with that, all pins verified! Just use those two rows furthest from the connector.
So, the kicad model I have for the microbit has a couple issues.
First, it only hooks up odd pins...meaning the top 2 rows of the connector array. I'd definitely prefer we did just the top and bottom; so I'm gonna have to do some electrical tests and play with the layout.
Second, the pin numbering isn't what I'd call intuitive....the "1" pin maps to ground (which is on the right of the connector), and goes right-to-left as pin numbers increase. I read left-to-right rather than right-to-left...so I'm gonna want to invert those.
Hmmmm...but then I noticed it works if you plug the microbit in on the bottom (connector on the top). So, tbd as to whether I'm gonna flip all those or not...but I'll probably do a new Repo for those Kicad libraries.
Got a first stab of the board layout. Changes:
- Screw-holes on bottom...meaning probably double-up the pins there?
- Desire to level-shift P0, P1, and P2...means go to the 8-bit level translator, and break out all 3.
- Need more room above the actual microbit connector pins
- Hole in the middle is a "wibni" for the speaker
- Bring level-shifted LED outputs for P1/2/3 separated a little more and shifted a little more right (away from barrel connector)
- Need to double-check barrel connector dimensions and pinout (Jeff has ordered them)
- Need to double-check switch spacings (Jeff has ordered them)