[TUHS] Codata restoration - day 1

[Warner Losh]

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 at 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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