Real Time Embedded Systems Monitor in Python?

[frikk]

Hey Everyone!
I've got a question regarding the capabilities of python in a real
time environment. I'll start by saying I'm a little bit flaky when it
comes to terminology, so please correct me or ask where it seems I'm
not beings specific or using the wrong wording.

I am looking into a project for the company I work for. Essentially
it involves setting up a real time monitor / signal injector in
between a CPU board and a system controller. The system controller
sends signals (message packets) to the CPU board. We would like to
create an environment where we can modify signals, inject new
messages, drop signals, etc. This would simulate communication
failures and message dropouts to see how the CPU board responds. The
application monitor would use a COM port to send and receive
messages. The most important part about this monitor is that
absolutely no messages get delayed or dropped due to inturrupts or lag
on the PC that the monitor is running on. What would be the expected
sampling time range that I could expect to handle?

I have seen similar applications written for other projects that we
have which were done in Visual Basic. I assume that if VB is up to the
task, Python should be as well. What kind of libraries am I looking
at? I will probably use wxWindows, but what about for the serial ports
and packet timing?

Like I said - I'm not sure what kind of "real time" this is - all I
know is that I need messages to not get dropped when they're received.

Thanks!
Blaine Booher

[Hendrik van Rooyen]

Re: Real Time Embedded Systems Monitor in Python?


"frikk" <frikker@gmail. comwrote:

>
I am looking into a project for the company I work for. Essentially
it involves setting up a real time monitor / signal injector in
between a CPU board and a system controller. The system controller
sends signals (message packets) to the CPU board. We would like to
create an environment where we can modify signals, inject new
messages, drop signals, etc. This would simulate communication
failures and message dropouts to see how the CPU board responds. The
application monitor would use a COM port to send and receive
messages. The most important part about this monitor is that
absolutely no messages get delayed or dropped due to inturrupts or lag
on the PC that the monitor is running on. What would be the expected
sampling time range that I could expect to handle?

What speed is the serial port running at? I have run a port at 115200 Baud
(albeit not carrying back to back packets), on a pentium II running Linux.

If you are not trying to do something insane like a Fast Fourier Transform in
real time, then Python should do the job for you - I would suggest you just
try it, starting with the smallest subset of commands - should take no longer
than about a week to get a prototype running.

When you say "in between" do you mean in one port and out of another?
So that you have to handle an upstream and downstream serial port?

The sampling time range will be directly (more or less, given some spillage
for turn around times) related to the baud rate, unless its a sort of sliding
window full duplex protocol. (I assume there is some sort of error
detection and recovery scheme - these normally waste about 10% of the
available bandwidth)

>
I have seen similar applications written for other projects that we
have which were done in Visual Basic. I assume that if VB is up to the
task, Python should be as well. What kind of libraries am I looking
at? I will probably use wxWindows, but what about for the serial ports
and packet timing?

Start off with a basic character interface, and use the serial module,
solving the protocol hassles first.
You can add the pretty pictures afterwards.

hth - Hendrik