[Arm-netbook] [EOMA68] RS232 on SoCs

[joem]

On Sat, 2013-08-31 at 14:36 +0100, luke.leighton wrote:
> On Sat, Aug 31, 2013 at 2:16 PM, Henrik Nordström
> <henrik at henriknordstrom.net> wrote:
> 
> > Yes, once the SoC is powered then there is no problem to connect 3.3V to
> > the RX pin. But it is generally not OK to provide power to an SoC I/O
> > pin with the I/O bank powered off.
> 
>  ... ah.  right.
> 
>  so, really, this should be noted in the EOMA68 specification, because
> i've added UART (not just for convenience but because it's needed for
> debugging as well as for programming / booting things like the STM32F
> on the flying squirrel).
> 
> so, really, hmmm... *ponders*.... actually this EOMA68-A20 CPU Card
> breaks the specification: the pins should be tri-state (floating).  i
> didn't realise the A20 would... arg ok.
> 
> so what's best here?

Don't use RS232 to USB converters that requires more than 3 pins to be
connected.