You can use tcpdump and wireshark to capture and analyse USB data.

mount -t debugfs / /sys/kernel/debug
modprobe usbmon

At this point you can just `cat /sys/kernel/debug/usb/usbmon/1u` to get 
an ascii representation of the USB traffic, meaning you'll probably have 
to write a parser, or you could use tcpdump to capture the data, and 
wireshark to analyse it.

tcpdump -i usbmon1 -w /tmp/usb_data.pcap
wireshark /tmp/usb_data.pcap

I don't have a suitable device to test wireshark's handling of NMEA with.

So this is more of a store then parse the data solution, rather than 
parse then store.  Maybe useful?  Depends a lot on what you want to do 
with it next.

Andrew



On 07/02/14 13:49, Andrew Mather wrote:
> Hi,
>
> I have recently added an AIS receiver to my gadget collection.  The
> device was supplied by Marinetraffic.com and is configured to send the
> data it receives via the internet to populate the live chart you see
> on the web page there.  There's a number of stations around the place,
> all of which contribute to the chart on a first-in best dressed basis
> for each position report.
>
> One of my areas of interest is VHF propagation and recently I noticed
> on my station's coverage graph that there had been some 'troppo' about
> and I had received signals from over 1000km away.  Unfortunately, the
> Marinetraffic website only shows a sliding 2-day window of coverage
> and so I "lost" the chance to grab a screenshot before I realised.
>
> The device (a Comar SLR300N) also has a USB port through which data
> can be captured locally.  I currently have this talking quite happily
> to OpenCPN on my Kubuntu machine and displaying the data received by
> my station, which I can compare against the live chart on the website.
>
> I'd like to be able to tap the USB output and grab the data as it
> comes off, parse it and store it locally so I can play around with it.
>   I have found various bits and pieces, that do part of the job, but my
> attempts to glue it all together have been a bit Heath-Robinson.
>
> I believe the device sends NMEA sentences.  I have verified this by
> using aisdispatcher and dumping the output and then using an online
> decoder/parser to view the data, but have not yet succeeded in setting
> it up to run a local routine without way more manual intervention than
> I want.
>
> Just wondering if anyone else has played with such devices and done a
> similar thing ?
>
>
> Andrew
>
>

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