[Interest] Is there a way to simulate serial port data?

[Roland Hughes]

I have to ask, why is it such a sin to have a stand alone program with a 
null modem cable and mini-tester as a testing tool. I have been working 
with serial ports off and on since the days of DOS 3.x and have always 
tested in this manner. The first piece of code one writes on a project 
which needs external inputs is the test tool to generate 1-N pre-defined 
inputs. There "should" be one laying around at the shop which was 
originally used to validate the product.

If you are dealing with a bug that only bites you ever so many years, I 
will leave you with this thought.

Having written a lot of scale software early in my career it was never 
the packet which had the problem that actually caused the problem, it 
was always a data packet 1-N in front of that packet. This happened 
because scale manufacturers would use bounding characters for differing 
packet types and they dutifully calculated a checksum or CRC for the 
packet. Inevitably that byte would collide with a value chosen for one 
of the bounding characters and it would be a seemingly random problem 
usually resulting from a truck being much lighter or heavier than any 
value they used to bench test their error checking byte with.

No idea what your serial project is, but that was always the problem we 
ran into in the field, especially when someone brought in a shiny new 
scale vendor or model.

If your system can be dynamically configured in the field, you should 
add a feature to keep track of the last 10 packets and when the code 
recognizes/traps the error (you obviously have some idea of what and 
where it manifests since you know it is a bug) dump the hex value of the 
last 10 packets to a log.

Won't fix your problem today or quickly, but it will actually identify 
what is causing the problem.

Or perhaps you have already done that and I'm just rambling...

-- 

Roland Hughes, President
Logikal Solutions
(630)-205-1593

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