[mythtv-users] AM2 Motherboard with PCI slots galore

[Yan Seiner]

Brian Wood
> Ronald Frazier wrote:
>
>>
>> Interesting. I had no idea those IR devices worked like that, or that
>> those adapters weren't true serial ports either. I've seen other
>> devices besides those adapter cables...thing in the form of a box that
>> had multiple (as many as 4) serial ports. I wonder if those suffer the
>> same problem or if they do a true emulation.
>
> I'm not sure what you mean by a "true" serial port. A USB-Serial adapter
> can be used for any application that meets the RS-232 spec, assuming you
> have good drivers for the adapter. It's the blasters that are not "true"
> serial devices.

Not quite....  You cannot toggle the RTS/DSR lines directly.  This messes
up some devices that need a specific timed handshake with those lines. 
LIRC with the homebrew serial receiver uses the CD line (IIRC) to sense
the IR signals and it needs precise timing of those signals.  Thus it
won't work on the USB serial ports.

> The multi-serial adapters that I have seen are also "true" serial
> devices in that they meet the RS-232 spec. Some use RJ type connectors,
> and some have external dongles as you mentioned. They were common back
> when we often used modem banks or terminal servers, they're not so
> common now.

Many of them leave off DSR/CTS/CD/etc lines; opting instead for just 3
lines:  Send, Receive, and Ground.

(This is a bit of a peeve of mine since I spent a couple of years working
around devices that *required* an AT keyboard or a timed signal on the RTS
line to reset.  Both are hard to come by when all you have in the field is
a laptop and a USB serial port....)

-- 
Windows is like a canary in a coal mine, it's the first thing to die on
your network.