Re: [hylafax-users] can't get a good connection

[Lee Howard <faxguy@xxxxxxxxxxxxxxxx>]

Jean-Pierre Radley wrote:

> Feb 24 19:02:06.46: [29720]: REMOTE wants 2400 bit/s
> Feb 24 19:02:06.46: [29720]: REMOTE wants A4 page width (215 mm)
> Feb 24 19:02:06.46: [29720]: REMOTE wants unlimited page length
> Feb 24 19:02:06.46: [29720]: REMOTE wants 3.85 line/mm
> Feb 24 19:02:06.46: [29720]: REMOTE wants 2-D MMR
> Feb 24 19:02:06.46: [29720]: REMOTE wants T.30 Annex A, 256-byte ECM
> Feb 24 19:02:06.46: [29720]: RECV training at v.27ter fallback mode 2400 bit/s
> Feb 24 19:02:06.46: [29720]: <-- [10:AT+FRM=24\r]
> Feb 24 19:02:07.76: [29720]: --> [7:CONNECT]
> Feb 24 19:02:09.32: [29720]: RECV: TCF 468 bytes, 0% non-zero, 460 zero-run
> Feb 24 19:02:09.34: [29720]: --> [10:NO CARRIER]
> Feb 24 19:02:09.34: [29720]: <-- [9:AT+FRS=7\r]
> Feb 24 19:02:09.46: [29720]: --> [2:OK]
> Feb 24 19:02:09.46: [29720]: TRAINING succeeded
>  

All of the TCF attempts through V.17 speeds and V.29 failed [from what I 
saw] due to too-short of zero-runs.  Finally V.27ter 2400 bps 
succeeds... which could mean a lot of things.  But the fact that the 
zero runs always seemed short seems to indicate that the modem is slow 
to train in the high-speed modes.  So the CONNECT message comes later 
than it should, and consequently some initial data is missed... and the 
missing TCF data causes a training failure, and so it goes until the 
speed is so slow that few-enough bytes are missed to prevent TCF from 
failing.

What kind of modem is /dev/tty1A ?

> Feb 24 19:02:10.80: [29720]: <-- [10:AT+FRM=24\r]
> Feb 24 19:02:12.40: [29720]: --> [7:CONNECT]
> Feb 24 19:02:12.82: [29720]: Bad HDLC terminating flag received.
> Feb 24 19:02:14.08: [29720]: HDLC frame not byte-oriented.  Trailing byte: 0xfc
> Feb 24 19:02:14.92: [29720]: HDLC frame not byte-oriented.  Trailing byte: 0x80
> Feb 24 19:02:17.44: [29720]: HDLC frame not byte-oriented.  Trailing byte: 0xf8
> Feb 24 19:02:19.57: [29720]: RECV received frame number 41
> Feb 24 19:02:19.57: [29720]: RECV frame FCS check failed
> Feb 24 19:02:19.57: [29720]: HDLC frame not byte-oriented.  Trailing byte: 0xc0
> Feb 24 19:02:22.09: [29720]: HDLC frame not byte-oriented.  Trailing byte: 0xf0
> Feb 24 19:02:23.81: [29720]: RECV received frame number 65
> Feb 24 19:02:23.81: [29720]: RECV received RCP frame
> Feb 24 19:03:11.65: [29720]: --> [10:NO CARRIER]
>  

But this looks rather bad.  At least at V.27ter 2400 bps the signal 
getting through is very poor.

> Feb 24 19:10:42.04: [29720]: RECV send PPR (partial page request)
> Feb 24 19:10:42.04: [29720]: RECV sent fourth PPR
> Feb 24 19:10:42.04: [29720]: <-- [9:AT+FRH=3\r]
> Feb 24 19:10:42.44: [29720]: --> [7:CONNECT]
> Feb 24 19:10:43.44: [29720]: --> [2:OK]
> Feb 24 19:10:43.44: [29720]: RECV recv DCN (disconnect)

The sender gave up... and I can certainly understand why.

So at this point you need to start trying to figure out why TCF is 
failing and why the modem is having such a hard time with the audio, at 
least at V.27ter 2400 bps.

Lee.

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