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Jan 23rd, 2007
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send raw data via serial

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Hi,

got a quick quickie...

Im trying to send commands to a micrcontroller via a USB->serial converter.

Im writing with wxPython on an XP machine it thats important.

I have been using the win32 module along with USPP and so far so good, apart from one thing. As far as i can work out it is only possible to write strings to the port as USPP uses a file handling style.

I am hoping to be able to send simple 8bit packets. I tried converting my data into the corresponding ASCII character and writing that to the port, but for anything lower than 0x20 it wont work as anything lower is an unprintable character...

Any help would be greatly appreciated.


Mark :mrgreen:
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Jan 24th, 2007
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Re: send raw data via serial

hmm... 20 views no replies...

Is this just a really difficult thing to do or have i missed something? done something wrong? i tried searching the forum but came up with nothing.

Thanks,


Mark
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Jan 24th, 2007
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Re: send raw data via serial

Mark, I think it is just a very specialized area. I did a lot of that kind of work in my earlier days using Delphi and the RS232 serial port. The modules (ADAM from Advantech Co., Ltd.) I used exchanged data as strings. It worked very well and was fun!

I trust you have taken a look at PyVisa:
http://pyvisa.sourceforge.net/
Last edited by vegaseat; Jan 24th, 2007 at 5:20 pm. Reason: info
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Jan 24th, 2007
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Re: send raw data via serial

I hadnt actually come across that before - i will dig around the siter and see what it unearths :-)

I feared this wasnt exactly a straight forward thing to do... never mind though - thats half the fun of programming :-)

Thanks for the link,


Mark
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Jan 25th, 2007
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Re: send raw data via serial

It almost seems like what you need is a simple C function to write the char to the port, and then link it in to your Python program.

Jeff
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Jan 25th, 2007
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Re: send raw data via serial

Click to Expand / Collapse  Quote originally posted by jrcagle ...
It almost seems like what you need is a simple C function to write the char to the port, and then link it in to your Python program.

Jeff
If you use Windows XP forget that, you can only get to the ports using the designated driver. The days you could go directly to a port are long gone!
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Jan 28th, 2007
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Re: send raw data via serial

Yeah - i tried writing a program a few months back in VC++ which ultimately ended in failure when i realised it was near impossible to access serial / parallel ports with out some SERIOUS knowledge of kernals / drivers etc... much more than the basics...

I was under the impression that Python was a lot more user friendly in this aspect and so far i would have to agree... but its this one thing is really holding me up :-(

If it is possible to write a string to the port... why is it not possible to write an int, or hex value?? ARGH! lol


Mark
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Jan 29th, 2007
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Re: send raw data via serial

Click to Expand / Collapse  Quote originally posted by MarkWalker84 ...
If it is possible to write a string to the port... why is it not possible to write an int, or hex value?? ARGH! lol
Wouldn't packing (http://docs.python.org/lib/module-struct.html) the data work for you?

Regards,
Greg
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Jan 29th, 2007
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Re: send raw data via serial

Python has full set of binary operators, but I don't think there is one way to send bitstring to USB chip. Ultimately that is how data would travel in the serial wire.
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Jan 29th, 2007
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Re: send raw data via serial

Its looking a lot like this cant be done...

So i think im going to have to do some sort of work around.

Just seems absolutely ridiculous to me that it is not possible to send binary / hex data to a serial port.


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