[Arm-netbook] rs232 level shifters

[luke.leighton]

On Tue, Nov 19, 2013 at 3:41 PM, mike.valk at gmail.com
<mike.valk at gmail.com> wrote:
>
> 2013/11/19 luke.leighton <luke.leighton at gmail.com>
>
>> On Tue, Nov 19, 2013 at 12:50 PM, mike.valk at gmail.com
>> <mike.valk at gmail.com> wrote:
>> > 2013/11/16 luke.leighton <luke.leighton at gmail.com>
>> >
>> >> On Sat, Nov 16, 2013 at 8:22 PM, Henrik Nordström
>> >> <henrik at henriknordstrom.net> wrote:
>> >> > lör 2013-11-16 klockan 13:23 +0000 skrev luke.leighton:
>> >> >> https://www.sparkfun.com/tutorials/215
>> >> >>
>> >> >> in the end i went with this for the router, using an IMD2A for the
>> >> >> two
>> >> >> transistors.
>> >> >
>> >> > Personally I haven't used RS232 in ages, only different "TTL" serial
>> >> > variants of 5V or 3.3V.
>> >>
>> >>  yehh i have to be reaasonably compatible with RS232, as this is
>> >> actually going to have a 9-pin header on it.  although the only thing
>> >> it will be connected to in most cases is one of those... yup, USB
>> >> serial converters.
>> >
>> >
>> > Why don't we include a USB to TTL-Serial chip on the card and/or
>> > carrier.
>>
>>  USB-to-TTL.... ah, because that would take out one of the 4 USB
>> ports.  in this "product" there's only 1 4-port hub.
>
>
> No, not on the hub. As as separate usb "slave" port.

 ok so free-standing effectively.  so the BOM comparison would be a
USB port (slave.  B is it?  like those you find on printers) plus
USB-to-serial converter IC vs a-bit-of-logic plus an RS232 DB9.  and
it would save a hell of a lot of board space - DB9s are big.

 hmm... it has merit.

l.