[Arm-netbook] [EOMA68] RS232 on SoCs

[luke.leighton]

On Sat, Aug 31, 2013 at 3:59 PM, Henrik Nordström
<henrik at henriknordstrom.net> wrote:
> lör 2013-08-31 klockan 10:23 -0400 skrev Ryan Mullen:
>> Hi Luke,
>>
>> Sorry, just to clear up my confusion - at what point does RS232 come
>> into play here?
>
> It doesn't. Only terminology confusion. Have given up on trying to
> correct people misuing RS232 term in these contexts.

 oops :)

>>  I was under the impression that the UART lines on the
>> EOMA connector were TTL, and so a USB<->serial adapter that can handle
>> 0-5V signals was what was needed (and is what I am using).
>
> The UART lines are not TTL compatible. Only 3.3V I/O supported.

 hm....

> Same problem is seen on at least i.MX233, and AM335x, and from what I
> can understand many other SoCs as well. Sometimes even clearly specified
> that you must not apply any power to I/O pins before powering the chip.

 ok so it's not just the A20.  and we can't realistically put a
boat-load of buffer ICs on such small boards, so i think the
standard's just gonna have to reflect how things are with the A20.
3.3V I/O levels (not 5.0V), proper power-down of I/O boards and so on.

 l.