[asterisk-bugs] [Asterisk 0018474]: [patch] "Caller*ID failed checksum" on Wildcard TDM2400P and TDM410

[Asterisk Bug Tracker]

The following issue requires your FEEDBACK. 
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https://issues.asterisk.org/view.php?id=18474 
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Reported By:                nivek
Assigned To:                rmudgett
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Project:                    Asterisk
Issue ID:                   18474
Category:                   Channels/chan_dahdi
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     feedback
Asterisk Version:           1.8.1 
JIRA:                       SWP-2751 
Regression:                 No 
Reviewboard Link:            
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Request Review:              
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Date Submitted:             2010-12-14 16:12 CST
Last Modified:              2011-03-02 13:44 CST
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Summary:                    [patch] "Caller*ID failed checksum" on Wildcard
TDM2400P and TDM410
Description: 
Receiving message "Caller*ID failed checksum" on every call.  Changing
"cidrw_gain" did nothing.  Other cid-based parameters did nothing.
Tested line using a analog phone with the Caller ID feature and received
caller id.

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 (0132535) rmudgett (administrator) - 2011-03-02 13:44
 https://issues.asterisk.org/view.php?id=18474#c132535 
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Bit 8 of 'b' is set when parity error.
Bit 9 of 'b' is set when framing error.

I think that your 'b' value looked like 0x02xx where bit 9 was set.
Am I correct in what your 'b' value looked like?

If only bits 8 or 9 are set then your first patch is better because the
checksum is the last character in the message and we can tolerate a
framing/parity error there.  The checksum character validates the message.

A framing error in the checksum could be because:
1) The sender did not send a full stop bit.
2) The sender cut off the FSK carrier too soon.
3) The sender opted to send zero of the specified zero to 10 trailing mark
bits and round-off errors in the code resulted in the code not being where
it thought it was in the demodulated bit stream. 

Issue History 
Date Modified    Username       Field                    Change               
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2011-03-02 13:44 rmudgett       Note Added: 0132535                          
2011-03-02 13:44 rmudgett       Status                   assigned => feedback
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