Serial port cable

[danielt]

(IIRC 3.3v is, strictly speaking, slightly over-volted too... but hopefully it is within engineering tolerances

not accordingly to the rk3399 datasheet, which claims 3.15 V as the acceptable maximum to that power domain.

I though that was the maximum for the power rail and the power rail is actually running at 3.0v (e.g. a 3.3v adapter will over-volt the RX pin by 0.3v, not 0.15v).

(when I bought my PBP I did also ordered some diodes with a forward drop of 0.3v and intended to use these to make hooking up an external programmer to the SPI FLASH strictly correct... however I'm not sure I can currently find them).

Edit:
Sorry, just realized I rather overlooked the obvious bit (I haven't looked the schematic for a while) which is that the engineering tolerance in the design doesn't come from the power rail anyway: it comes the 100 ohm resistors in series with TX and RX.