[Coco] raspberry pi 3 model b to coco serial cable

[Joel Rees]

2017/11/05 7:37 "Mathieu Bouchard" <matju at artengine.ca>:
>
> Le 2017-11-04 à 16:47:00, David Ladd a écrit :
>
>> RS232 has ranges of -25V to +25V depending on the status of the bit.
Those
>> kind of voltages would damage the Raspberry Pi's GPIO if you directly
>> connected them to the CoCo's bitbanger without the level shifter.
>
>
> In practice, which devices ever really used the full ±25V range instead
of just ±12V ?

I believe we had a bit of such in the oilfield equipment where I grew up,
1960s or so. I never workedwith it but some of my friends did, and we saw
some in the classroom at the community college. You'll see a bit of such
circuitry in power distribution systems and such.  Many applications where
simplicity is more important than convenience.

I'd guess Gene could tell us about something specific in the broadcast
industry. Or, perhaps, his lathe.

The range was for connection, not function. If you know the endpoints of
your connection are rPI and coco, you really don't need to cover the whole
range. just don't forget and try to hook the converter to something you
don't know, if you do.