Parsing Nexmon .pcap files

[munir01]

Thank you for this amazing work! I have a question about parsing CSI and RSSI data using csiread. If I know that the CSI data was collected using RPi 4B using this precompiled binary of Nexmon, is there a way to tell if I should use csiread.Nexmon or csiread.NexmonPull46? Alternatively, given a .pcap file, how can I decide if we should use csiread.Nexmon or csiread.NexmonPull46? I would like to get RSSI in addition to CSI and the only way to get it through csiread.NexmonPull46

Also, there is no csiread.NexmonPull46.read() function. So, I created a similar one like csiread.Nexmon.read(), which basically calls super().read().

Here is the sample code that I am using:

csi_file_path = './abc.pcap'
csidata = csiread.NexmonPull46(csi_file_path, chip='43455c0', bw=80) 
csidata.read()
csidata.display(0)

Here is the output:

63045 packets parsed
0th packet:
  file                : ./abc.pcap
  count               : 63045
  nano                : False
  sec                 : 1720688287
  usec                : 331678
  caplen              : 1084
  wirelen             : 1084
  magic               : 0x1111
  src_addr            : 7c:10:c9:e0:20:dc
  seq                 : 0
  core                : 0
  spatial             : 0
  chan_spec           : 0xe02a
  chip_version        : 0x65
  csi                 : (256,)
  rssi                : 192
  fc                  : 148

Looking at value 192, does it look like it is reading the correct RSSI?

Thank you!

[citysu]

1. When using NexmonPull46, if magic number is 0x1111 and rssi (1byte) is not 0x11 and fc (1byte) is not 0x11, your choice is right. infer_device function in example/utils.py can also tell you which one should be used.
2. NexmonPull46 inherits Nexmon in _csiread.pyx, NexmonPull46.read() does exist (but is not wrapped in core.py, maybe I forgot it ?).
3. _autoscale in NexmonPull46 is 0 while it is 1 in Nexmon. This was introduced in nexmon_csi pull 256. You can set csidata._autoscale = 1 before calling csidata.read() if you don't think the change is right.

[munir01]

Thank you for the prompt response. To follow up,

1. By looking at the values of my magic number (0x1111), rssi (192, not 0x11), and fc (148, not 0x11), I think I should be able to NexmonPull46
2. Yes, I do not see that function in core.py. But I added it manually.
3. I did try autoscale, but the values remain the same. Here is the code:

   csidata = csiread.NexmonPull46(csi_file_path, chip='43455c0', bw=80) 
   csidata._autoscale = 1
   csidata.read()
   csidata.display(0)

   My concern with RSSI value is that 192 does not seem a reasonable value. But when I used CSIKit library to parse the same file, I get RSSI value -64 for the first packet. I noticed that 192-256=-64. Is there an issue for parsing the RSSI bytes? Thanks again!

[citysu]

-64 is right, I'll fix it. You can also use csidata.rssi.astype(np.int8) to fix the value by yourself.

[munir01]

csidata.rssi.astype(np.int8) works like a charm! Will do. Thanks a lot!