I got back to my Windows 2000 system and looked more carefully at the
driver.  It turns out there are 3 drivers on the disk which Windows is
willing to install.  After picking the one that had the best sounding
pathname given my system, the USB adapter worked like it did on the Windows
XP Home system.  The path to this driver was quite different than the one
shown in the installation instructions that came with the unit.

The converter would work with an EasyProg with my loopback adapter inserted
in between, but would not work directly.  This adapter has pins 1-4-6
shorted and 7-8 shorted at the COM port end.  I suspected that it probably
was only responding to CTS and not DSR or DCD.  To test this I opened pins
1, 4, and 6.  It still worked as I expected.  So, this USB serial adapter
has a bug where it wants CTS driven even when RTS/CTS flow control is
expclicitly disabled in the software.

I then modified an EasyProg by shorting pins 7 and 8 on the bottom of the
DB-9 connector.  This allowed the USB serial port to work with the EasyProg
directly without any adapter.  It was still slower than a real serial port.
Programming a full 16F876 and reading it back at two voltages took 64.2
seconds instead of 55.5 with a real serial port.  That's 16% slower, which
may be acceptable in many cases.


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Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com
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