Byron A Jeff wrote:
> On Thu, Jul 20, 2006 at 11:18:34PM +0200, Wouter van Ooijen wrote:
>   
>>> It just starts the same round of arguments that always seem 
>>> to float around
>>> when this discussion starts. Most of the time you talk to JDM and Tait
>>> style programmer advocates, they are looking for cheap, 
>>> simple, and instant
>>> gratification. 
>>>       
>> Note that I am not saying that such programmers don't have their place.
>> If your time is cheap by all means try one or two, if they work, fine!
>> But if they don't drop them, and try a design that has a much higher
>> chance of working, but costs a little more. Adding a level booster to a
>> dumb programmer combines the bad aspects of both: it is still a serial
>> port pin wiggler with all the associated XP problems, but the complexity
>> approaches a Wisp628 or other simple but intelligent programmer.
>>     
>
> I'm a firm non-believer in serial ports because of their varibility.
> Unfortunately because of USB both serial and parallel ports are slowly
> dying with no guarantees either will be available in the near future.
> I'll be sorely disappointed when we get to the point where a programmer
> cannot be bootstrapped simply because the interface complexity prohibits
> it. Right now USB to serial converters seems to be the only type of 
> interface that may survive the purge. This has steered my interest in
> figuring out how to bootstrap from them.
>
> BAJ
>   
I have done several designs with USB converters. I agree, its just about 
all that is left.

I realize that USB is replacing parallel ports and serial ports left and 
right, but USB has proven
(to my mind) to be incredibly unreliable, at least under Windows.

The main problem with USB VCP is that there is no visibility. If there 
is an error, there is almost
no ability to see what is wrong. The comm port moves all over the place, 
forcing the user code to
test all available VCP ports to locate your "product". You can't 
reliably bit-bang anything, the timing
is unreliable.

I've tested myriad Win2K, Win98, and  WinXP systems using USB. Win98 
will gladly accept multiple
copies of the same driver. Win2K and WinXP systems are afflicted with 
"Windows sickness"... it just
stops working, no idea why.

A product I am now finishing the firmware on accepts USB (VCP) ports or 
a DB9 connection. The
DB9 connection is infinitely more reliable than the VCP port. Tested 
with 7 different WinXP systems.

--Bob
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