(03-11-2020, 01:00 PM)zaius Wrote:(03-11-2020, 08:53 AM)danielt Wrote: Basically a TTL serial device "parks" at logic high and will always send out 3.3v or 5v when it is not sending characters. In other words unless you are actively typing then there isn't really anything except for the voltage being applied to the RX pin that could be causing the board to hang.
So if high logic makes it hang, then why wouldn't 3.3V on a 3.3V input still make it hang? I'm not saying that using an adapter with a 5V output isn't a problem. I'm questioning whether there might be two problems — a voltage problem and a logic problem.
(From the little I've read, it sounds as though some chipsets park outputs at a high impedance state, so the input is floating rather than held high or low.)
5v is not really logic high (from the Pinebook's point of view), it is over-volting the I/O pins.
So far on the Pinebook Pro forums I have seen multiple independant failure reports with the Pine64 3.5mm serial adapter (over-volting), multiple independant success reports with a variety of different 3.3v adapters (logic high) and, unless I have overlooked something, no failure reports with 3.3v adapters.
3.3v adapters could cause touble (IIRC 3.3v is, strictly speaking, slightly over-volted too... but hopefully it is within engineering tolerances). However if they do cause trouble why are we not getting failure reports for that?
