Stephan Rose <> wrote in
news

_ :
> On Sun, 17 Jun 2007 19:11:30 -0400, Richard Urban wrote:
>
>> It is called a communication port (ex. = Com1). It is up to the
>> device manufacturer to provide software that works within Vista. I
>> have a UPS connected to Com1. Vista doesn't see it.
>>
>> Serial ports are dead technology and I don't ever expect that my UPS
>> will be able to communicate with Vista.
>>
>
> Actually Serial Ports are very much alive. It's exceedingly annoying
> to have a PC without a Serial Port if you do software development for
> embedded hardware. Especially when working with smaller processors
> that are not powerful enough for Ethernet/USB or where having anything
> beyond a serial port would just add too much cost to a device.
It sure can be a costly addition, although you'd be suprised that
sometimes an embedded module w/eth may only cost $5-$10 more than the
same model, except w/o eth.
>
> There are many applications where a serial port is beyond sufficient
> where trying to use Ethernet or USB would be like swatting a fly with
> a nuke! Not to mention the simplicity of a serial port VS Ethernet or
> USB. USB especially is a pain to deal with.
>
> Takes a single instruction to send a byte over Serial.
>
> Takes by magnitudes more code to do the same via either ethernet or
> usb, not to mention transmission overhead. They are also unsuitable
> actually for certain types of communications where you only need to
> transmit a single byte of information and need an immediate response
> in real-time without packet overhead that is by magnitudes larger than
> the actual data.
I concur. Many of the (serial-based) wireless systems we have sold are
doing very fast time-slotted polling, in the range of 100ms per
poll/response. There is no way to get that performance via ethernet. We
also have remote I/O gear that transfers I's at one end to O's at the
other (and visa-versa), and the response time of that is under 25ms from
the edge transition at one end to the output at the other end being set.
Oh yeah, the complete compiled code for the entire I/O functionality is
< 60K in size. And that includes a menu based UI as well.
The poject I am just starting uses ethernet, and just initializing the
CPU module with TCP/IP, doing absolutely nothing else except making it
appear as an active IP on the network, the compiled code is 130K. This is
before any functionality at all, to do anything, is added.