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jfrenzel

CAN decode on a Cerebot?

Question

I have one of the older Cerebot boards which should be equivalent to the Diglent Pro MX7 Embedded Systems Trainer Board that is currently for sale. I would like to capture CAN traffic using an Analog Discovery module and Waveforms software. I have two basic questions.

After studying related posts on this forum, I get the strong sense that Analog Discovery and Waveforms software are better suited for connecting to the "PIC side" of the transceivers (RX and TX), rather than CAN side, where CANH and CANL are differential signals.

(1) Is this correct?

After studying the Cerebot schematic and reference manual, it appears that I can't directly connect to RX and TX for either CAN1 or CAN2. However, it appears that if I short together all of three pins of JP1 and all three pins of JP2, then the RX and TX of CAN1 will be available on pins 1 and 4 of connector JF.

As far as I can tell, shorting all three pins together will not create an electrical short, as nothing on the board is driving the outside pins of JP1 and JP2.

(2) Is this correct?

Thanks!

 

Edited by jfrenzel

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2 answers to this question

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Hi @jfrenzel

1. The Analog Discovery DIOs are supplied at 3v3 and have input logic level threshold at ~1.5V or 0.5V.
The 3v3/0v "PIC" signals are suitable to interface.
To analyze higher voltages (like CANL/H) a series resistor is recommended to reduce the current sink through the protection to internal 3v3 and/or voltage divider for logic level adaptation.

2. I don't see any obstacle in connecting all the 3 pins together on JP1 or JP2.

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