|
| From: | Bas Prins |
| Subject: | Re: [lwip-users] lwip-users Digest, Vol 214, Issue 8 |
| Date: | Mon, 7 Jun 2021 23:23:15 +0200 |
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Today's Topics:
1. Re: pppos sent packets optionally start with 0x7e, why?
(Rüdiger Asche)
----------------------------------------------------------------------
Message: 1
Date: Mon, 7 Jun 2021 23:12:08 +0200
From: Rüdiger Asche <ruediger_asche@t-online.de>
To: "Mailing list for lwIP users" <lwip-users@nongnu.org>
Subject: Re: [lwip-users] pppos sent packets optionally start with
0x7e, why?
Message-ID: <BA745CE95ED940CCB793BEA922328F28@RACTOMCOVE>
Content-Type: text/plain; charset="utf-8"
Hi Bas,
if you have access to the ISO 3309 spec which defines HDLC, look for the statement
"A single flag may be used as both the closing flag for one frame and the opening flag for the next frame."
in chapter 4.1.
I suspect that this explains the observation you make. The closing frame character of the last frame is recycled as the frame start character for the next frame, remembered by the peer.
The easiest way to verify this is to look at the HDLC frame parser and -generator in lwip. I can't tell you where to look since it's been decades I worked with PPP (never under lwip), but it shouldn't be too hard to find in the code base.
Thanks Rüdiger
----- Original Message -----
From: Bas Prins
To: lwip-users@nongnu.org
Sent: Monday, June 07, 2021 10:43 PM
Subject: Re: [lwip-users] lwip-users Digest, Vol 214, Issue 6
Dear Rüdiger ,
Thanks for the detailed answer and the link (haven't read that, learned a lot from reading).
When I read this, I understand what you mentioned, and that the sender is allowed to omit the TRAILING 0x7e byte. But in my case, it's not really the trailing byte (or I am still missing the obvious here... :))
It might be hard to digest from the CSV data, but this is what I can see in my logic analyzer:
STM starts (after modem reaches data mode):
0x7e ..... 0x7e - send first packet, wrapped in 0x7e bytes.
After roughly 500us the peer replies:
0x7e ...... 0x7e - again a ppp packet wrapped in 0x7e bytes
STM responds and sends a second packet:
0xFF .. 0x7e : This is what struck me. Shouldn't this BEGIN with a 0x7e?
It already sent it's "omitable leading 0x7e byte" to enclose the first packet. So it should start with a 0x7e byte now, right? Or does the peer accept the trailing 0x7e byte of the FIRST sent packet as leading 0x7e for the second packet??
I interpreted this part as the FIRST 0x7e byte of the second sent PPP packet is omitted.
What am I still missing?
Best regards, bas
Op ma 7 jun. 2021 om 21:28 schreef <lwip-users-request@nongnu.org>:
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When replying, please edit your Subject line so it is more specific
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Today's Topics:
1. Re: pppos sent packets optionally start with 0x7e, why?
(Rüdiger Asche)
----------------------------------------------------------------------
Message: 1
Date: Mon, 7 Jun 2021 21:27:33 +0200
From: Rüdiger Asche <ruediger_asche@t-online.de>
To: "Mailing list for lwIP users" <lwip-users@nongnu.org>
Subject: Re: [lwip-users] pppos sent packets optionally start with
0x7e, why?
Message-ID: <F01ACCC173FC4DFB8EC67D8A6C1E9859@RACTOMCOVE>
Content-Type: text/plain; charset="utf-8"
Hi there Bas,
have you looked at the HDLC encoding rules? In https://en.wikipedia.org/wiki/Point-to-Point_Protocol , about half way down, it reads
"0x7E, omitted for successive PPP packets"
for the frame END character. So to me it looks as if it's not the leading frame character but the trailing one that's missing, which is specification compliant. Makes sense too to omit it because the inner structure of a frame past the sync char allows for full parsing of a well formed packet (of course taking into account the negotiated PFC and AFC compression restrictions). Note that the first LCP packet (decoded here) is still fully framed:
ff03 c021 1 1 => LCP conf request
0 14 => length
2 6 0 0 0 0 =>
5 6 40 b1 9c e9 => magic number
7 2 => Protocol field compression
8 2 => AFC compression
38 b7 => => frame checksum
Afterwards, both sides have all the information they need to parse a peer's frame without a trailing framing character.
----- Original Message -----
From: Bas Prins
To: lwip-users@nongnu.org
Sent: Monday, June 07, 2021 7:00 PM
Subject: Re: [lwip-users] pppos sent packets optionally start with 0x7e, why?
I think the CSV attachment was dropped by server. Trying to add the CSV as plain text below.
Async Serial == RX
Async Serial [1] == TX
Leading 0x7E byte is not provided by LWIP in when it calls sio_write.
name type start_time duration data
Async Serial [1] data 5.80629 8.25E-05 0x41
Async Serial [1] data 5.806378 8.25E-05 0x54
Async Serial [1] data 5.806466 8.25E-05 0x0D
Async Serial [1] data 6.936377 8.25E-05 0x2B
Async Serial [1] data 6.946236 8.25E-05 0x2B
Async Serial [1] data 6.95636 8.25E-05 0x2B
Async Serial data 7.865252 8.25E-05 0x0D
Async Serial data 7.865339 8.25E-05 0x0A
Async Serial data 7.865426 8.25E-05 0x4F
Async Serial data 7.865513 8.25E-05 0x4B
Async Serial data 7.865599 8.25E-05 0x0D
Async Serial data 7.865686 8.25E-05 0x0A
Async Serial [1] data 7.869666 8.25E-05 0x41
Async Serial [1] data 7.869754 8.25E-05 0x54
Async Serial [1] data 7.869842 8.25E-05 0x4F
Async Serial [1] data 7.86993 8.25E-05 0x0D
Async Serial data 7.871056 8.25E-05 0x0D
Async Serial data 7.871143 8.25E-05 0x0A
Async Serial data 7.87123 8.25E-05 0x43
Async Serial data 7.871317 8.25E-05 0x4F
Async Serial data 7.871403 8.25E-05 0x4E
Async Serial data 7.87149 8.25E-05 0x4E
Async Serial data 7.871577 8.25E-05 0x45
Async Serial data 7.871664 8.25E-05 0x43
Async Serial data 7.871751 8.25E-05 0x54
Async Serial data 7.871837 8.25E-05 0x20
Async Serial data 7.871924 8.25E-05 0x31
Async Serial data 7.872011 8.25E-05 0x31
Async Serial data 7.872098 8.25E-05 0x35
Async Serial data 7.872185 8.25E-05 0x32
Async Serial data 7.872271 8.25E-05 0x30
Async Serial data 7.872358 8.25E-05 0x30
Async Serial data 7.872445 8.25E-05 0x0D
Async Serial data 7.872532 8.25E-05 0x0A up until here is AT commands to put modem in ppp. That succeeded here.
Async Serial [1] data 7.895673 8.25E-05 0x7E First packet sent over uart from STM
Async Serial [1] data 7.895761 8.25E-05 0xFF
Async Serial [1] data 7.895849 8.25E-05 0x7D
Async Serial [1] data 7.895937 8.25E-05 0x23
Async Serial [1] data 7.896025 8.25E-05 0xC0
Async Serial [1] data 7.896113 8.25E-05 0x21
Async Serial [1] data 7.896201 8.25E-05 0x7D
Async Serial [1] data 7.896289 8.25E-05 0x21
Async Serial [1] data 7.896377 8.25E-05 0x7D
Async Serial [1] data 7.896465 8.25E-05 0x21
Async Serial [1] data 7.896553 8.25E-05 0x7D
Async Serial [1] data 7.896641 8.25E-05 0x20
Async Serial [1] data 7.896729 8.25E-05 0x7D
Async Serial [1] data 7.896817 8.25E-05 0x34
Async Serial [1] data 7.896905 8.25E-05 0x7D
Async Serial [1] data 7.896993 8.25E-05 0x22
Async Serial [1] data 7.897081 8.25E-05 0x7D
Async Serial [1] data 7.897169 8.25E-05 0x26
Async Serial [1] data 7.897257 8.25E-05 0x7D
Async Serial [1] data 7.897345 8.25E-05 0x20
Async Serial [1] data 7.897433 8.25E-05 0x7D
Async Serial [1] data 7.897521 8.25E-05 0x20
Async Serial [1] data 7.897609 8.25E-05 0x7D
Async Serial [1] data 7.897697 8.25E-05 0x20
Async Serial [1] data 7.897785 8.25E-05 0x7D
Async Serial [1] data 7.897872 8.25E-05 0x20
Async Serial [1] data 7.89796 8.25E-05 0x7D
Async Serial [1] data 7.898048 8.25E-05 0x25
Async Serial [1] data 7.898136 8.25E-05 0x7D
Async Serial [1] data 7.898224 8.25E-05 0x26
Async Serial [1] data 7.898312 8.25E-05 0x40
Async Serial [1] data 7.8984 8.25E-05 0xB1
Async Serial [1] data 7.898488 8.25E-05 0x9C
Async Serial [1] data 7.898576 8.25E-05 0xE9
Async Serial [1] data 7.898664 8.25E-05 0x7D
Async Serial [1] data 7.898752 8.25E-05 0x27
Async Serial [1] data 7.89884 8.25E-05 0x7D
Async Serial [1] data 7.898928 8.25E-05 0x22
Async Serial [1] data 7.899017 8.25E-05 0x7D
Async Serial [1] data 7.899105 8.25E-05 0x28
Async Serial [1] data 7.899193 8.25E-05 0x7D
Async Serial [1] data 7.899281 8.25E-05 0x22
Async Serial [1] data 7.899369 8.25E-05 0x38
Async Serial [1] data 7.899457 8.25E-05 0xB7
Async Serial [1] data 7.899545 8.25E-05 0x7E end first packet
Async Serial data 7.900403 8.25E-05 0x7E first received ppp packet on rx line
Async Serial data 7.90049 8.25E-05 0xFF
Async Serial data 7.900576 8.25E-05 0x7D
Async Serial data 7.900663 8.25E-05 0x23
Async Serial data 7.90075 8.25E-05 0xC0
Async Serial data 7.900837 8.25E-05 0x21
Async Serial data 7.900924 8.25E-05 0x7D
Async Serial data 7.90101 8.25E-05 0x21
Async Serial data 7.901097 8.25E-05 0xE5
Async Serial data 7.901184 8.25E-05 0x7D
Async Serial data 7.901271 8.25E-05 0x20
Async Serial data 7.901358 8.25E-05 0x7D
Async Serial data 7.901444 8.25E-05 0x39
Async Serial data 7.901531 8.25E-05 0x7D
Async Serial data 7.901618 8.25E-05 0x22
Async Serial data 7.901705 8.25E-05 0x7D
Async Serial data 7.901792 8.25E-05 0x26
Async Serial data 7.901878 8.25E-05 0x7D
Async Serial data 7.901965 8.25E-05 0x20
Async Serial data 7.902052 8.25E-05 0x7D
Async Serial data 7.902139 8.25E-05 0x20
Async Serial data 7.902226 8.25E-05 0x7D
Async Serial data 7.902312 8.25E-05 0x20
Async Serial data 7.902399 8.25E-05 0x7D
Async Serial data 7.902486 8.25E-05 0x20
Async Serial data 7.902573 8.25E-05 0x7D
Async Serial data 7.90266 8.25E-05 0x23
Async Serial data 7.902746 8.25E-05 0x7D
Async Serial data 7.902833 8.25E-05 0x25
Async Serial data 7.90292 8.25E-05 0xC2
Async Serial data 7.903007 8.25E-05 0x23
Async Serial data 7.903094 8.25E-05 0x7D
Async Serial data 7.90318 8.25E-05 0x25
Async Serial data 7.903267 8.25E-05 0x7D
Async Serial data 7.903354 8.25E-05 0x25
Async Serial data 7.903441 8.25E-05 0x7D
Async Serial data 7.903528 8.25E-05 0x26
Async Serial data 7.903614 8.25E-05 0x26
Async Serial data 7.903701 8.25E-05 0xA6
Async Serial data 7.903788 8.25E-05 0x32
Async Serial data 7.903875 8.25E-05 0x2F
Async Serial data 7.903962 8.25E-05 0x7D
Async Serial data 7.904049 8.25E-05 0x27
Async Serial data 7.904135 8.25E-05 0x7D
Async Serial data 7.904222 8.25E-05 0x22
Async Serial data 7.904309 8.25E-05 0x7D
Async Serial data 7.904396 8.25E-05 0x28
Async Serial data 7.904483 8.25E-05 0x7D
Async Serial data 7.904569 8.25E-05 0x22
Async Serial data 7.904656 8.25E-05 0xD7
Async Serial data 7.904743 8.25E-05 0x73
Async Serial data 7.90483 8.25E-05 0x7E
Async Serial data 7.904917 8.25E-05 0x7E
Async Serial data 7.905003 8.25E-05 0xFF
Async Serial data 7.90509 8.25E-05 0x7D
Async Serial data 7.905177 8.25E-05 0x23
Async Serial data 7.905264 8.25E-05 0xC0
Async Serial data 7.905351 8.25E-05 0x21
Async Serial data 7.905437 8.25E-05 0x7D
Async Serial data 7.905524 8.25E-05 0x22
Async Serial data 7.905611 8.25E-05 0x7D
Async Serial data 7.905698 8.25E-05 0x21
Async Serial data 7.905785 8.25E-05 0x7D
Async Serial data 7.905871 8.25E-05 0x20
Async Serial data 7.905958 8.25E-05 0x7D
Async Serial data 7.906045 8.25E-05 0x34
Async Serial data 7.906132 8.25E-05 0x7D
Async Serial data 7.906219 8.25E-05 0x22
Async Serial data 7.906305 8.25E-05 0x7D
Async Serial data 7.906392 8.25E-05 0x26
Async Serial data 7.906479 8.25E-05 0x7D
Async Serial data 7.906566 8.25E-05 0x20
Async Serial data 7.906653 8.25E-05 0x7D
Async Serial data 7.906739 8.25E-05 0x20
Async Serial data 7.906826 8.25E-05 0x7D
Async Serial data 7.906913 8.25E-05 0x20
Async Serial data 7.907 8.25E-05 0x7D
Async Serial data 7.907087 8.25E-05 0x20
Async Serial data 7.907173 8.25E-05 0x7D
Async Serial data 7.90726 8.25E-05 0x25
Async Serial data 7.907347 8.25E-05 0x7D
Async Serial data 7.907434 8.25E-05 0x26
Async Serial data 7.907521 8.25E-05 0x40
Async Serial data 7.907608 8.25E-05 0xB1
Async Serial data 7.907694 8.25E-05 0x9C
Async Serial data 7.907781 8.25E-05 0xE9
Async Serial data 7.907868 8.25E-05 0x7D
Async Serial data 7.907955 8.25E-05 0x27
Async Serial data 7.908042 8.25E-05 0x7D
Async Serial data 7.908128 8.25E-05 0x22
Async Serial data 7.908215 8.25E-05 0x7D
Async Serial data 7.908302 8.25E-05 0x28
Async Serial data 7.908389 8.25E-05 0x7D
Async Serial data 7.908476 8.25E-05 0x22
Async Serial data 7.908562 8.25E-05 0xD3
Async Serial data 7.908649 8.25E-05 0xDE
Async Serial data 7.908736 8.25E-05 0x7E end first received ppp packet
Async Serial [1] data 7.913322 8.25E-05 0xFF second ppp packet sent by STM, why is the 0x7E byte ommitted? I also attached debugger to get data bytes provided by LWIP, first byte is -0xFF
Async Serial [1] data 7.91341 8.25E-05 0x7D
Async Serial [1] data 7.913498 8.25E-05 0x23
Async Serial [1] data 7.913586 8.25E-05 0xC0
Async Serial [1] data 7.913674 8.25E-05 0x21
Async Serial [1] data 7.913762 8.25E-05 0x7D
Async Serial [1] data 7.91385 8.25E-05 0x24
Async Serial [1] data 7.913938 8.25E-05 0xE5
Async Serial [1] data 7.914026 8.25E-05 0x7D
Async Serial [1] data 7.914114 8.25E-05 0x20
Async Serial [1] data 7.914202 8.25E-05 0x7D
Async Serial [1] data 7.91429 8.25E-05 0x29
Async Serial [1] data 7.914378 8.25E-05 0x7D
Async Serial [1] data 7.914466 8.25E-05 0x23
Async Serial [1] data 7.914554 8.25E-05 0x7D
Async Serial [1] data 7.914642 8.25E-05 0x25
Async Serial [1] data 7.91473 8.25E-05 0xC2
Async Serial [1] data 7.914818 8.25E-05 0x23
Async Serial [1] data 7.914906 8.25E-05 0x7D
Async Serial [1] data 7.914994 8.25E-05 0x25
Async Serial [1] data 7.915082 8.25E-05 0x7A
Async Serial [1] data 7.91517 8.25E-05 0xEF
Async Serial [1] data 7.915258 8.25E-05 0x7E
Async Serial data 7.915929 8.25E-05 0x7E
Async Serial data 7.916016 8.25E-05 0xFF
Async Serial data 7.916102 8.25E-05 0x7D
Async Serial data 7.916189 8.25E-05 0x23
Async Serial data 7.916276 8.25E-05 0xC0
Async Serial data 7.916363 8.25E-05 0x21
Async Serial data 7.91645 8.25E-05 0x7D
Async Serial data 7.916536 8.25E-05 0x21
Async Serial data 7.916623 8.25E-05 0xE6
Async Serial data 7.91671 8.25E-05 0x7D
Async Serial data 7.916797 8.25E-05 0x20
Async Serial data 7.916884 8.25E-05 0x7D
Async Serial data 7.916971 8.25E-05 0x34
Async Serial data 7.917057 8.25E-05 0x7D
Async Serial data 7.917144 8.25E-05 0x22
Async Serial data 7.917231 8.25E-05 0x7D
Async Serial data 7.917318 8.25E-05 0x26
Async Serial data 7.917405 8.25E-05 0x7D
Async Serial data 7.917491 8.25E-05 0x20
Async Serial data 7.917578 8.25E-05 0x7D
Async Serial data 7.917665 8.25E-05 0x20
Async Serial data 7.917752 8.25E-05 0x7D
Async Serial data 7.917839 8.25E-05 0x20
Async Serial data 7.917925 8.25E-05 0x7D
Async Serial data 7.918012 8.25E-05 0x20
Async Serial data 7.918099 8.25E-05 0x7D
Async Serial data 7.918186 8.25E-05 0x25
Async Serial data 7.918273 8.25E-05 0x7D
Async Serial data 7.918359 8.25E-05 0x26
Async Serial data 7.918446 8.25E-05 0x26
Async Serial data 7.918533 8.25E-05 0xA6
Async Serial data 7.91862 8.25E-05 0x32
Async Serial data 7.918707 8.25E-05 0x2F
Async Serial data 7.918793 8.25E-05 0x7D
Async Serial data 7.91888 8.25E-05 0x27
Async Serial data 7.918967 8.25E-05 0x7D
Async Serial data 7.919054 8.25E-05 0x22
Async Serial data 7.919141 8.25E-05 0x7D
Async Serial data 7.919227 8.25E-05 0x28
Async Serial data 7.919314 8.25E-05 0x7D
Async Serial data 7.919401 8.25E-05 0x22
Async Serial data 7.919488 8.25E-05 0x46
Async Serial data 7.919575 8.25E-05 0xDA
Async Serial data 7.919661 8.25E-05 0x7E
Async Serial [1] data 7.9253 8.25E-05 0xFF
Async Serial [1] data 7.925388 8.25E-05 0x7D
Async Serial [1] data 7.925476 8.25E-05 0x23
Async Serial [1] data 7.925564 8.25E-05 0xC0
Async Serial [1] data 7.925652 8.25E-05 0x21
Async Serial [1] data 7.92574 8.25E-05 0x7D
Async Serial [1] data 7.925828 8.25E-05 0x22
Async Serial [1] data 7.925916 8.25E-05 0xE6
Async Serial [1] data 7.926004 8.25E-05 0x7D
Async Serial [1] data 7.926092 8.25E-05 0x20
Async Serial [1] data 7.92618 8.25E-05 0x7D
Async Serial [1] data 7.926268 8.25E-05 0x34
Async Serial [1] data 7.926356 8.25E-05 0x7D
Async Serial [1] data 7.926444 8.25E-05 0x22
Async Serial [1] data 7.926532 8.25E-05 0x7D
Async Serial [1] data 7.92662 8.25E-05 0x26
Async Serial [1] data 7.926708 8.25E-05 0x7D
Async Serial [1] data 7.926796 8.25E-05 0x20
Async Serial [1] data 7.926884 8.25E-05 0x7D
Async Serial [1] data 7.926972 8.25E-05 0x20
Async Serial [1] data 7.92706 8.25E-05 0x7D
Async Serial [1] data 7.927149 8.25E-05 0x20
Async Serial [1] data 7.927237 8.25E-05 0x7D
Async Serial [1] data 7.927325 8.25E-05 0x20
Async Serial [1] data 7.927413 8.25E-05 0x7D
Async Serial [1] data 7.927501 8.25E-05 0x25
Async Serial [1] data 7.927589 8.25E-05 0x7D
Async Serial [1] data 7.927677 8.25E-05 0x26
Async Serial [1] data 7.927765 8.25E-05 0x26
Async Serial [1] data 7.927853 8.25E-05 0xA6
Async Serial [1] data 7.927941 8.25E-05 0x32
Async Serial [1] data 7.928029 8.25E-05 0x2F
Async Serial [1] data 7.928117 8.25E-05 0x7D
Async Serial [1] data 7.928205 8.25E-05 0x27
Async Serial [1] data 7.928293 8.25E-05 0x7D
Async Serial [1] data 7.928381 8.25E-05 0x22
Async Serial [1] data 7.928469 8.25E-05 0x7D
Async Serial [1] data 7.928557 8.25E-05 0x28
Async Serial [1] data 7.928645 8.25E-05 0x7D
Async Serial [1] data 7.928733 8.25E-05 0x22
Async Serial [1] data 7.928821 8.25E-05 0xAD
Async Serial [1] data 7.928909 8.25E-05 0xB3
Async Serial [1] data 7.928997 8.25E-05 0x7E
Async Serial [1] data 7.929411 8.25E-05 0xFF
Async Serial [1] data 7.929499 8.25E-05 0x03
Async Serial [1] data 7.929587 8.25E-05 0x80
Async Serial data 7.929658 8.25E-05 0x7E
Async Serial [1] data 7.929675 8.25E-05 0x21
Async Serial data 7.929744 8.25E-05 0xFF
Async Serial [1] data 7.929763 8.25E-05 0x01
Async Serial data 7.929831 8.25E-05 0x7D
Async Serial [1] data 7.929851 8.25E-05 0x01
Async Serial data 7.929918 8.25E-05 0x23
Async Serial [1] data 7.929939 8.25E-05 0x00
Async Serial data 7.930005 8.25E-05 0xC0
Async Serial [1] data 7.930027 8.25E-05 0x0A
Async Serial data 7.930092 8.25E-05 0x21
Async Serial [1] data 7.930115 8.25E-05 0x03
Async Serial data 7.930178 8.25E-05 0x7D
Async Serial [1] data 7.930203 8.25E-05 0x06
Async Serial data 7.930265 8.25E-05 0x2B
Async Serial [1] data 7.930291 8.25E-05 0x00
Async Serial data 7.930352 8.25E-05 0xE7
Async Serial [1] data 7.930379 8.25E-05 0x00
Async Serial data 7.930439 8.25E-05 0x7D
Async Serial [1] data 7.930467 8.25E-05 0x00
Async Serial data 7.930526 8.25E-05 0x20
Async Serial [1] data 7.930555 8.25E-05 0x00
Async Serial data 7.930612 8.25E-05 0x7D
Async Serial data 7.930699 8.25E-05 0x28
Async Serial data 7.930786 8.25E-05 0x26
Async Serial data 7.930873 8.25E-05 0xA6
Async Serial data 7.93096 8.25E-05 0x32
Async Serial data 7.931046 8.25E-05 0x2F
Async Serial data 7.931133 8.25E-05 0x74
Async Serial data 7.93122 8.25E-05 0xC1
Async Serial data 7.931307 8.25E-05 0x7E
Async Serial [1] data 7.931541 8.25E-05 0x13
Async Serial [1] data 7.931629 8.25E-05 0x28
Async Serial [1] data 7.931717 8.25E-05 0x7E
Async Serial data 7.93236 8.25E-05 0x7E
Async Serial data 7.932447 8.25E-05 0x80
Async Serial data 7.932534 8.25E-05 0x21
Async Serial data 7.93262 8.25E-05 0x01
Async Serial data 7.932707 8.25E-05 0xFD
Async Serial data 7.932794 8.25E-05 0x00
Async Serial data 7.932881 8.25E-05 0x04
Async Serial data 7.932968 8.25E-05 0x2C
Async Serial data 7.933054 8.25E-05 0xB0
Async Serial data 7.933141 8.25E-05 0x7E
Async Serial data 7.933228 8.25E-05 0x7E
Async Serial data 7.933315 8.25E-05 0x80
Async Serial data 7.933402 8.25E-05 0x21
Async Serial data 7.933488 8.25E-05 0x03
Async Serial data 7.933575 8.25E-05 0x01
Async Serial data 7.933662 8.25E-05 0x00
Async Serial data 7.933749 8.25E-05 0x0A
Async Serial data 7.933836 8.25E-05 0x03
Async Serial data 7.933922 8.25E-05 0x06
Async Serial data 7.934009 8.25E-05 0x0A
Async Serial data 7.934096 8.25E-05 0x81
Async Serial data 7.934183 8.25E-05 0x4B
Async Serial data 7.93427 8.25E-05 0x67
Async Serial data 7.934356 8.25E-05 0xCA
Async Serial data 7.934443 8.25E-05 0xA1
Async Serial data 7.93453 8.25E-05 0x7E
Async Serial [1] data 7.939163 8.25E-05 0xFF
Async Serial [1] data 7.939251 8.25E-05 0x03
Async Serial [1] data 7.939339 8.25E-05 0x80
Async Serial [1] data 7.939427 8.25E-05 0x21
Async Serial [1] data 7.939515 8.25E-05 0x03
Async Serial [1] data 7.939603 8.25E-05 0xFD
Async Serial [1] data 7.939691 8.25E-05 0x00
Async Serial [1] data 7.939779 8.25E-05 0x0A
Async Serial [1] data 7.939867 8.25E-05 0x03
Async Serial [1] data 7.939955 8.25E-05 0x06
Async Serial [1] data 7.940043 8.25E-05 0x00
Async Serial [1] data 7.940131 8.25E-05 0x00
Async Serial [1] data 7.940219 8.25E-05 0x00
Async Serial [1] data 7.940307 8.25E-05 0x00
Async Serial [1] data 7.940395 8.25E-05 0x6B
Async Serial [1] data 7.940483 8.25E-05 0x1A
Async Serial [1] data 7.940571 8.25E-05 0x7E
Async Serial [1] data 7.941107 8.25E-05 0xFF
Async Serial [1] data 7.941195 8.25E-05 0x03
Async Serial data 7.9412 8.25E-05 0x7E
Async Serial [1] data 7.941283 8.25E-05 0x80
Async Serial data 7.941287 8.25E-05 0x80
Async Serial [1] data 7.941371 8.25E-05 0x21
Async Serial data 7.941374 8.25E-05 0x21
Async Serial [1] data 7.94146 8.25E-05 0x01
Async Serial data 7.94146 8.25E-05 0x01
Async Serial data 7.941547 8.25E-05 0xFE
Async Serial [1] data 7.941548 8.25E-05 0x02
Async Serial data 7.941634 8.25E-05 0x00
Async Serial [1] data 7.941636 8.25E-05 0x00
Async Serial data 7.941721 8.25E-05 0x04
Async Serial data 7.941808 8.25E-05 0x48
Async Serial data 7.941894 8.25E-05 0x5F
Async Serial data 7.941981 8.25E-05 0x7E
Async Serial [1] data 7.942683 8.25E-05 0x0A
Async Serial [1] data 7.942771 8.25E-05 0x03
Async Serial [1] data 7.942859 8.25E-05 0x06
Async Serial [1] data 7.942947 8.25E-05 0x0A
Async Serial [1] data 7.943035 8.25E-05 0x81
Async Serial [1] data 7.943123 8.25E-05 0x4B
Async Serial [1] data 7.943211 8.25E-05 0x67
Async Serial [1] data 7.943299 8.25E-05 0xFD
Async Serial [1] data 7.943387 8.25E-05 0xC1
Async Serial [1] data 7.943475 8.25E-05 0x7E
Async Serial data 7.944092 8.25E-05 0x7E
Async Serial data 7.944178 8.25E-05 0x80
Async Serial data 7.944265 8.25E-05 0x21
Async Serial data 7.944352 8.25E-05 0x02
Async Serial data 7.944439 8.25E-05 0x02
Async Serial data 7.944526 8.25E-05 0x00
Async Serial data 7.944612 8.25E-05 0x0A
Async Serial data 7.944699 8.25E-05 0x03
Async Serial data 7.944786 8.25E-05 0x06
Async Serial data 7.944873 8.25E-05 0x0A
Async Serial data 7.94496 8.25E-05 0x81
Async Serial data 7.945046 8.25E-05 0x4B
Async Serial data 7.945133 8.25E-05 0x67
Async Serial data 7.94522 8.25E-05 0xEA
Async Serial data 7.945307 8.25E-05 0x5B
Async Serial data 7.945394 8.25E-05 0x7E
Async Serial [1] data 7.949159 8.25E-05 0xFF
Async Serial [1] data 7.949247 8.25E-05 0x03
Async Serial [1] data 7.949335 8.25E-05 0x80
Async Serial [1] data 7.949423 8.25E-05 0x21
Async Serial [1] data 7.949511 8.25E-05 0x02
Async Serial [1] data 7.949599 8.25E-05 0xFE
Async Serial [1] data 7.949687 8.25E-05 0x00
Async Serial [1] data 7.949775 8.25E-05 0x04
Async Serial [1] data 7.949863 8.25E-05 0x3E
Async Serial [1] data 7.949951 8.25E-05 0x54
Async Serial [1] data 7.950039 8.25E-05 0x7E
Op ma 7 jun. 2021 om 16:19 schreef Bas Prins <bas.prins3@gmail.com>:
Dear,
I was looking at the data being sent/received over uart when ppp is being negotiated. I was surprised to see that the received byte stream is always wrapped in 0x7e bytes (leading + trailing).
But for some reason this is not the case for the bytes lwip sends (/provides to my sio_write function). Even stronger, sometimes it does start with a leading 0x7e, sometimes it doesn't.
On the wiki I read:
"PPP packets all start and end with 0x7E. If you don't see these, something is wrong with your low level driver"
When I look at fsm.c where the PPP header is created, I don't see 0x7e being added as part of the opening header.
pppos works, lwip works, I can open sockets, download from FTP, etc. So what's the deal with this? Should I investigate further and is there a bug sitting in my code? Or is this "perfectly normal" behavior and is the wiki wrong?
I added the logic analyzer export to this email.
Hopefully someone can shed some light on this.
best regards, bas
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