On Wed, Sep 21, 2005 at 04:06:56PM +0200, Wouter van Ooijen wrote:
> > Couldn't this be solved by using a MAX232 or similar, looping 
> > the signal
> > through itself for a voltage boost?
> > Power would be taken from USB or PS/2 connectors (but then 
> > you could as
> > well use a Wisp628 anyway).
> 
> You would loose the no-external-power appeal of the seial-port-powered
> programmers. If you have power available you might (as you say) as 2well
> use a propper programmer :)

No real disagreement there. But the programmer issue is always something
that I see as a "chicken and egg" type problem. To get a "proper" programmer
you need a programmer, though it may be a temporary one.

So I believe there is value in a "no smarts" programmer, even if it's
only purpose is to serve as a code dumper to get to a smart programmer.

My Trivial programmers have served this purpose with parallel ports for
several years. However there is no doubt that parallel ports are a dying
breed, and pretty much dead on laptops. Serial will soon be completely
gone too in my estimation. USB has challenges because it has to be smart
to operate. 

I see USB to serial cables as a potential stopgap, because they are smart
enough, and they are reasonably cheap. However I believe we've all seen
reports about the suspect drivers and modem signals not well synchronized
with the RX, TX signals. Both the WISP628 and the EasyProg only depend on a 3
wire RX/TX/GND connection to function. JDM needs a real serial port with
properly synchronized modem signals to function. There simply are not such
guarantees in the PC serial port market now.

So that's why I'm working on my Trivial Serial BootStrap Programmer. The
preliminary design page is here:

http://www.finitesite.com/d3jsys/tbs555

As built I can properly latch the PIC data with the PIC clock. However
The reverse RX channel isn't working yet. Also I'm now thinking that for
robustness it'll either need a MAX232 or use a transistor based level
shifter a la your El Cheapo that you used to use for WLoader.

It's not a "proper" programmer in the least. But it can server the purpose
of a code dumper when all you have is a serial port that honors RX and TX
only. And unfortunately I think we're going to see more and more of those
as time progresses.

BAJ
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