I'm writing a dissector in wireshark for parse received packets. As we know there three types of RLC packet, that are TM, UM and AM RLC PDU. But how could I know the type of received packet?
There is an LTE RLC dissector in the official sources, see:
- https://code.wireshark.org/review/gitweb?p=wireshark.git;a=blob;f=epan/dissectors/packet-rlc-lte.c
- https://code.wireshark.org/review/gitweb?p=wireshark.git;a=blob;f=epan/dissectors/packet-rlc-lte.h
There are several pieces of information, including the RLC mode, that are not contained in the frame and must be told to the dissector in order for it to decode the PDU properly. In the header file, see struct rlc_lte_info.
It is then up to the calling dissector, e.g. the LTE MAC dissector, to correctly fill in this context information before calling the RLC dissector.
TM RLC PDUs are usually control channel information (BCCH, DL/UL CCCH and PCCH) This where you can indirectly discern TM from AM/UM RLC PDUs. As with UMTS there is no specific bit flag to tell you what mode the PDU is. example excerpt from specs docs.
3GPP TS 36.322 Evolved Universal Terrestial Radio Access (E-UTRA)
....... page 11
An AM RLC entity delivers/receives the following RLC data PDUs:
AMD PDU;
AMD PDU segment.
An AM RLC entity delivers/receives the following RLC control PDU:
STATUS PDU.
.......
Thus you have to follow to the letter what the RLC rules are implemented on this release of the specs. You have to check if line 344 in (https://code.wireshark.org/review/gitweb?p=wireshark.git;a=blob;f=epan/dissectors/packet-rlc-lte.c) follows the rules in 3GPP TS 36.322 Evolved Universal Terrestial Radio Access (E-UTRA).
By the value of logical channel ID.
Related
I've been exploring the ADAM 6717 from Advantech.
This is the ModBus address table for said device:
At first I wanted to modify the value of the Digital output channel 0(DO0), so, as can be seen from the picture above, such address is the 0x0017.
I succeed at this by using a ModBus tool and the following settings:
Sending either "On" or "Off", turns On and off a LED connected to that output. Everything runs smoothly according to my expectation up to this point.
The problem arises when I want to read the Analog Input channel 6 or equivalently, address 400431~40044.
Since that address lies on the Analog Output Holding Registers part of the address table, I though that the following settings would accomplish the job:
However, as can be seen above, the reading shows 0.0 when there is actually 6V connected to that input (a potentiometer)
It is worth mentioning that I've made sure to enable the AI6 channel as well as setting it to Voltage mode instead of current. Also, the web utility for the device shows the AI6 reading correctly as I change the potentiometer's resistance value.
So the problem doesn't lie in the connection from the potentiometer to the AI6 but somewhere else.
Out of nothing and leaving aside what I think I know on this topic, I though of changing the function from 0x03 to 0x04
However, the response is exactly the same.
It bugs me that I can read and write values to the output coils but not the Analog output holding registers.
Is there any configuration that I might be missing over here?
Thanks in advance.
Device settings:
IP address: 10.0.0.1
Port in which the ModBus service is running: 5020
I am struggling trying to implement a packet burst. My data are in a binary file. What I want to do is to send my data in the flow N times per seconds, let's say 2, to simulate a burst transmission.
The "Message Strobe block" seems to be a good candidate but I don't understand how to use it.
Here the (uncorrect) flow I want to have in my transmitter side:
I tried to get insight from
Simple GNU Radio Eventstream Based Burst Extraction and Plotting and
Burst Transmission in GNU Radio Sample Streams with Eventstream without success :(
Thank you a lot
If you have already binary input you have to generate a PDU/message to use Eventstream like shown here. As you can see the flowgraph in the article simply adds up the samples produced from noise source and burst transmission. Then you only have to time messages delivered to the Eventstream block. Maybe you can make use of packetized modems freshly introduced with GNU Radio 3.7.10.
I used the message strobe block and I build my own block to read a file, build a pmt message and output it directly as a new pdu. It seems to work perfectly well that way :)
I'm collecting 802.11 packets using scapy on Ubuntu 16.04 (4.4 kernel). The RadioTap headers for my packets have the following present flags:
present=TSFT+Flags+Rate+Channel+dBm_AntSignal+b14+b29+Ext
Given the description of RadioTap, I would expect Channel to start on the 10th byte following the header and preceding fields (8 for TSFT + 1 each for Flags and Rate). Channel has an alignment of 2, so there is no need for padding. Yet this is what is in the undecoded portion of the packet:
notdecoded=' \x08\x00\x00\x00\x00\x00\x00f\xc0 \x02\x00\x00\x00\x00\x10\x02l\t\xa0\x00\xa9\x00\x00\x00\xa9\x00'
In this case the channel number actually appears at bytes 18-19 ('l\t' = 2412), and im not sure exactly what byte contains the dBm signal strength.
Anyone have an idea as to what i'm missing?
Found the answer after digging into the spec a bit deeper:
Scapy doesn't parse extended headers as signified by bit-32 (though it did tell me about them by stating +Ext above). Those extra headers are stuffed on the front of 'notdecoded' section of the packet. I think scapy should, at minimum, remove those extended headers from not-decoded to avoid future confusion.
In this particular case there are two extra 32 bit extended bitmap headers, accounting for the extra 8 bytes.
If someone wants to write an answer up with more detail, ill accept it, otherwise i will clean this answer up and accept it for perpetuity.
I have the Panasonic MN63Y1210 tag. I have read it with different phones and always I see that the ID is 0x00000000
I've made a program with Arduino and Adafruit's PN532 shield and I have that response too, in ATQB, the PUPI appears like 0x00000000, but when I read the ISO 14443-3 I read this:
A Pseudo-Unique Identifier (PUPI) is used to differenciate PICCs
during anticollision. This 4-byte number may be either a number
dinamically generated by the PICC or a diversified fixed number. The
PUPI shall only be generated by a state transition form the POWER-OFF
to the IDLE state.
For the transition from POWER OFF to IDLE, we need a field, so, I expect that when I try to read the tag this is not in POWER OFF, because I'm applying a field, but I think it is strange to have that PUPI of 0x00000000. I've tested with another tag (same Panasonic model) and I get the same PUPI...
Is this normal? Or what do you think about it?
I would suggest that you start by looking into the datasheet of the MN63Y1210:
On page 26 (table 3-13) you will find that the default value this chip uses for the PUPI is 00000000. You can configure that value, for instance, over the serial interface.
How do I interpret dwParam1 from the midiInProc delegate into midi status message like note-off, or note-on, control change?
Because as long i try dwParam1 is 254, and is not equal to note-off or anything else.
You won't necessarily receive note-offs from every input device. IIRC it is legal for a device to send a note-on with volume=0 as a substitute for note-off. Also a drum stream (from a drum machine and/or on MIDI channel 10) I believe commonly contains only note-ons, no note-offs.
Given that your question mentions dwParam1 and midiInProc, I'm assuming this is for Windows. When you receive MIM_DATA in your midiInProc, you can parse dwParam1 as follows:
For the status byte (command and channel), use LOBYTE(dwParam1).
For the first data byte, use HIBYTE(dwParam1).
If applicable, for the second data byte, use LOBYTE(HIWORD(dwParam1)).
I'm not entirely sure what you are asking, but I think you are trying to figure out how to interpret MIDI data.
I suggest this resource:
http://www.midi.org/techspecs/midimessages.php
MIDI messages related to notes are differentiated by the first 4 bits, not by the whole byte. The last four bits of the first byte specify the channel.
The answer by #Conrad Albrecht is mostly right, but I wanted to chip in with an answer (instead of a comment), as I think that the original poster is probably being confused by MIDI running status.
If you are seeing bytes which don't resemble normal MIDI status bytes, you can assume that they are of the same type as the previous byte which you received. Therefore it is not only legal, but very common, to use MIDI note on events with velocity of 0 as a substitute for MIDI note offs.
You should just interpret these bytes as the normal second two bytes of a MIDI note on event.