[Info-vax] [OT] Serial ports as GPIO devices, was: Re: OpenVMS 5.5 shared folder on a windows network ?

[FredK]

"Simon Clubley" <clubley at remove_me.eisner.decus.org-Earth.UFP> wrote in 
message news:i3gu18$9jv$1 at news.eternal-september.org...
> On 2010-07-29, John Wallace <johnwallace4 at yahoo.co.uk> wrote:
>>
>> The fact that parallel printer ports weren't designed to do simple
>> digital IO hasn't stopped them being used for it quite extensively in
>> the world of low-cost electronic interfaces. In some of those cases,
>> in a modern PC the parallel port chip (or its SuperIO replacement)
>> simply isn't there for some vendor's custom driver to talk to. There's
>> no way that kind of hardware change from parallel to USB can be fixed
>> without heartache of some kind, however much good work various good
>> folks may have done for USB printers.
>>
>
> The control lines on the serial port can also be used for this.
>
> At home, I am using a AVR programming circuit which is attached to the
> serial port control lines and the programmer uses those control lines
> to implement the AVR programming protocol.
>
> There's no way you could do that on a USB serial port with the latency
> involved.
>

It'll only cost a couple bucks to find out :-)