Usb - Pro/Con

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Wed Sep 22 20:36:47 2004

> >>> I don't like the fact that you're supposed to pay for an ID
> >>> (and have thr device 'certified') if you want to make your
> >>> own stuff. Never had this problem with RS232 :-)
>
> You need to pay for and get certified if you are going to make a legitimate
> network appliance also [MAC ID]. Of course most products purchase a

You didn't need to pay for anything if you wanted to make an RS232 device.

> pre-sertified module. Same if you are going to create a cellular product [I
> happen to use WaveCom modules in mine].
>
> >>> And the fact that you seem to need special drivers for many
> >>> devices which you can bet are not available for any of my machines.
>
> Although I can not find the link at presend, there is source code for low
> level drivers. Since your environment (by choice) is the use of equipment

Ah, sop now if I buy a product the first thing I have to do is write
special drivers for it..... And hope that I can get enough of a spec on
the product to allow me to do this.

> that is not currently supported, rooling your own drivers seems reasonable
> to me.
>
> >>> And the fact that it's very assymmetric (there are 'masters' and
> >>> 'slaves') is something I don't like either. RS232 was much
> >>> more symmetrical.
>
> RS-232 is an ELECTRICAL Specification. The protocols that are run on
> This are independand. Lets keep it apple and apples.....

OK, Asynchronous bit-serial data, sent LSB first, using the RS232 voltage
and connector specifications :-)

> >>> More modern palmtops have USB ports. They're slaves,
> >>> designed to hang off a PC. You can't link them directly to
> >>> a printer. It's interesting that some of my older handhelds
> >>> have HPIL ports, but by default the handheld is the loop
> >>> controller ('master'), so you can link them straight to a
> >>> printer. But they can be 'slaves' if you want to link them
> >>> to a larger machine. We've gone backwards (as usual)
> >>>
>
> To be honest, I have not looked into the electricals on this. I am NOT sure
> that they are *REQUIRED* to be slaves.

There is, of course, nothing rreally to stop you making a handheld
'master' (althoguh the master has to supply power to all devices on the
USB chain), but the fact remains that AFAIK all handheld machines
currently on sale are 'slaves'

> >>> All my PCs have ISA slots only. Other machines have Unibus,
> >>> Qbus, BBC 1MHz bus/Torch X-bus, various custom I/O slots
> >>> (like on th HP9830), HPIL, PERQlink, etc. Just about all of
> >>> those have RS232 (or compatible) ports, I've nver seen USB
> >>> for any of them
> >>>
>
> Again, development boards ARE out their that give you everything you need to
> interface to nearly any host...

Most of the developemnt boards I've looked at assume you're making a
slave device. This is not what I need.


>
> >>> > I also don't understand your statement that it is not a bus.....
> >>>
> >>> Electrically it's not a bus. If it was, I could just parallel up
> >>> connectors and plug in several devices, there'd be no need
> >>> to _always_
> >>> have a hub (which, from what I've seen, contains a fair
> >>> amount of logic).
>
> By that argument (which has valid aspects), then ArcNet was not a bus
> either, and RS-232 is DEFINITELY not a bus architecture (it is purely point
> to point).

No argument there. But neither of those claim to be a bus.

-tony
Received on Wed Sep 22 2004 - 20:36:47 BST