CAN Inspector: a CAN node to sample the CAN bus waveforms

Dear CAN bus gurus,

I've been thinking of a design for a CAN node that is able to digitize the waveform on CANH and CANL and then transmit the waveform as multiple CAN messages. The device would also be able to report the CAN power supply voltage. I'm interested in your opinions on this concept.

The design is based around the Texas Instruments ADC08B200 ADC, which digitizes to 8-bits at up to 200 Msps. Its key feature is a 1 kB data buffer that can be read out slowly, so there is no need for the MCU to keep up with the data in realtime.

The motivation for wanting such a device is that I'm using a CAN bus for some remote experiments in Antarctica, and there have been several cases recently where the bus has operated in a degraded mode (CANL shorted to ground, missing terminator - this is on a 70m long bus running at 100 kbps) without anyone being awareof it. The people who are servicing the equipment do not have the expertise or the time to connect up TDRs or oscilloscopes or even multimeters to diagnose problems. The physical environment can be very tough, e.g,. -40C in summer (-80C in winter) and high altitude (over 4000m), so asking someone to connect an oscilloscope and make measurements is asking a lot. The personnel are only on-site for betwen 5 and 21 days over summer each year; the rest of the time the equipment is
  entirely remote.

A "CAN Inspector" node that could be simply placed on the bus would be very valuable. I could remotely monitor the bus, recognise when problems occur, and give repair instructions. An alternative approach could be a small USB-accessible oscilloscope.

One of the big advantages of CAN is its fault tolerance. However, if the fault occurred some years ago, and you are already running in a degraded mode, then you have already used up all your tolerance.

I will post a link to a draft schematic for the CAN Inspector in a subsequent message.

Regards, Michael
-- 
Professor Michael Ashley                   Department of Astrophysics
University of New South Wales       http://www.phys.unsw.edu.au/~mcba
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