How to flush the data accumulated in COM port buffer

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hi monks, I have program that issues commands to device that are attached to COM port and collects the response and then does the pattern matching.Now , i have a command whose response takes some time and that too comes in bits and pieces.I am able to collect that response that i want ,but remaining response keeps on coming even after i completed with that command , when i issue the next commmand the response i get is the leftout response in RX buffer of the previous command. i need to discard the data in the buffer before issuing the next command.How can i do this ? I appreciate your help Thanks, westar.

Comment on How to flush the data accumulated in COM port buffer

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Re: How to flush the data accumulated in COM port buffer by fizbin (Chaplain) on Mar 18, 2005 at 18:42 UTC
First off, it's incredibly hard to read your question. Please fix that. Secondly, as for your question itself, you seem to be asking "how can I clear out any characters waiting in the input buffer for a particular filehandle". The easiest way to accomplish this is with the `Term::ReadKey` module: `use Term::ReadKey; # ... do some stuff to the filehandle COMPORT ... # ... do the command that gives the long response ... # Clear the remaining input while (defined(ReadKey(0.1,COMPORT))) {} # ... do some other command ...` [download] That code will pull characters until the RX buffer is empty and will wait 0.1 seconds on an empty RX buffer to decide that it's really done. You can use "-1" if you want it to exit as soon as the RX buffer is empty and not wait. I do hope that you're using sysread or some similar unbuffered system to deal with serial ports - otherwise, you'll have all sorts of trouble. `-- @/=map{[/./g]}qw/.h_nJ Xapou cets krht ele_ r_ra/; map{y/X_/\n /;print}map{pop@$_}@/for@/` [download]	[reply] [d/l] [select]

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Re: How to flush the data accumulated in COM port buffer
by fizbin (Chaplain) on Mar 18, 2005 at 18:42 UTC

Secondly, as for your question itself, you seem to be asking "how can I clear out any characters waiting in the input buffer for a particular filehandle". The easiest way to accomplish this is with the Term::ReadKey module:

use Term::ReadKey;
# ... do some stuff to the filehandle COMPORT ...
# ... do the command that gives the long response ...

# Clear the remaining input
while (defined(ReadKey(0.1,COMPORT))) {}
# ... do some other command ...
[download]

I do hope that you're using sysread or some similar unbuffered system to deal with serial ports - otherwise, you'll have all sorts of trouble.

--
@/=map{[/./g]}qw/.h_nJ Xapou cets krht ele_ r_ra/;
map{y/X_/\n /;print}map{pop@$_}@/for@/
[download]

[reply]
[d/l]
[select]