[time-nuts] TBOLT communication
buehl
buehl at superlink.net
Wed Sep 24 09:02:33 EDT 2008
Nevil:
In my business we use/ supply serial to parallel converters for
programming our product originally designed for serial. We ran into
most of the problems you have described. The hanging appears to be a
windows problem (we use XL pro mostly). Ours uses the Prolific
converter and driver.
We found that there are signal voltage level problems associated with
the use of the USB as power source.
This appears to be much worse with laptops than with desktop
computers. We can take the same 'setup' and move it from a
non-functioning laptop connection, and make it work well on a
desktop. Seems that for power savings the laptop makers are reducing
current levels and voltage levels to the lowest values possible; thus
not enough level out of the converter.
An S-P converter with its own power supply should help if it is
designed to up-convert the serial levels to RS 232 standards.
One of the things we did to help this was to reduce the required
serial levels in our product. Of course you cannot change the
tunderbolt parameters.
Since our cable must be computer powered, one of the things I have
wanted to try (never enough time) is shift the serial signal up above
ground by a small amount. Thought was to use a small button cell in
the serial output line.
Thus instead of the serial signal going from 0 to 3.5V, it would go
from 1 to 4.5V or similar. My thought is that serial device logic
does not actually require 0V for low logic state, and the extra volt
on the high side would improve reliability of HI logic state.
If you want to contact me off-line: buehl at superlink.net
Tom Buehl
At 06:58 PM 9/24/2008 +1000, you wrote:
>Hi,
>I have just spent a week or two trying to talk to a Trimble Thunderbolt.
>I have a laptop running VISTA, about which there is little to say.
>The laptop has no serial ports, but I have some USB/Serial converters
>that successfully run
>my HP 3815A and a Samsung GCRU/D, and also communicate with my HOBO
>loggers.
>The USB/Serial converters are a little difficult to use, sometimes
>hanging, necessitating
>unplugging and plugging back in. They get assigned to various Port
>numbers but tend to keep
>the same number from day to day. The ports can be configured in the
>management function.
>However the TBOLT refuses to talk to the converter, to the extent
>that I thought that I must have
>damaged the TBOLT.
>Today, as a last resort, I remembered an old PC, dragged it out and
>stoked it up, and to my delight
>the TBOLT monitoring program ran without difficulty under Windows
>2000 with a conventional serial port.
>Now I vaguely remember talk about RS232 communications and the need
>for pull up or down
>resistors and supplies, but searching the archives I could find
>nothing relevant.
>Can anyone tell me how I could run the TBOLT off a USB/Serial converter?
>cheers, Neville Michie
>
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