11 Oct
2014
11 Oct
'14
2:37 a.m.
These days, you can buy 5.0V or 3.3V to USB adapters in the hobbyist or robotics section
of many computer stores. I’ve used them to trouble shoot blown driver chips to verify they
really were toast. Be careful of the voltage levels, though, since many 3.3V products
can’t tolerate 5.0V…
Warner
On Oct 10, 2014, at 2:13 PM, Hans Rosenfeld <rosenfeld(a)grumpf.hope-2000.org> wrote:
Hi Michael,
On Fri, Oct 10, 2014 at 05:26:58PM +0000, Engel, Michael wrote:
The serial cable is working, we tried all sorts
of handshake configurations.
If we get any characters back (the system is running at 9600 baud, I tried
all combinations of 7/8 bit, none/even/odd/mark/space parity and 1/2 stop
bits), these are garbled and contain mostly "1" bits (0xfc, 0xfe, 0xff or
similar).
The UART itself seems to work (exchanged it with the one from the non
working board - same result), so now I suspect the AM26LS32 RS423
driver to be the culprit.
I've had that a few times with PDP11s and VAXen from the 80s. The line
receivers suddenly died, showing exactly the symptoms you describe.
Those were different chips (ua96XX), but the concept is the same.
Replacing them with newer chips from the same family worked without
problems.
Hans
--
%SYSTEM-F-ANARCHISM, The operating system has been overthrown
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