Thanks Collin80, I think I did my due diligence with the design but I've never used CAN so it makes sense to ask those that have.

Mind you the same applies to just about everything on this board

I've replaced the RS resistors with two digital pots, mostly because I was desperate for some more CPU pins and doing that freed up 4 of them.

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Rob

That makes sense, AFAIK all register access with CMSIS is performed through structures that mimic the physical registers, anything that packs the structs will cause havoc.


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Rob

You're thinking of IDE as Integrated Development Environment.

Quite right, at my age one's memory doesn't go back that far

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Rob

the 80 conductor ribbon cable version of an IDE cable.

What is this cable? The IDE is software it doesn't really have a cable, but if it did it would be the USB cable.

Oh hang on, IDC. Ok as vasquo says it's easy to make your own, get the parts and squeeze the halves onto the cable in a vice.

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Rob

will using RS485 be a good solution?

Yes but there may be simpler ways, EG just tri-state buffers or software control of the IO pins.

What is distance and speed of the link?

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Rob

Because of the lack of reverse current protection in the regulator chip, we need to use a jumper to select the power source.

Can you bump the regulator output a bit and pass it through a schottky diode?

Does anyone see a requirement to have a 5V 3A continuous supply on an Arduino platform?

3A might be nice but if you currently have 2.4A I would think that's enough. It's heaps better that any standard Arduino.

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Rob

As some will know I am working on a new Due-style board, it will have both the SAM's CAN ports broken out to transceivers with the current circuit being as follows.



Are there any CAN experts here that can comment on this and/or suggest modifications?

NUP2202W1 is an ESD protection device.

MCP4242 is a digital pot, I may use that instead of the resistors to set the slew rate.

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Rob

Another problem with this sort of project is reliably detecting the human, a PIR will only detect movement, if they sit still for 5 minutes it will think they have left the room.

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Rob

[totally]

One can only assume that the guys writing the code got it right and a function called micros() actually has a resolution of 1uS. If that was not the case I'm sure we would have heard about it by now.

if the prescaler is 64 in the stock Arduino code,

I'm not familiar with the code but the hardware is totally different, any prescaler referred to in AVR code will have no bearing on ARM code. On an ARM I would think they are reading the systick counter directly.

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Rob

Documentation is one of the most neglected fields IMO, probably because not many people like doing it at any time much less at the end of a project when you want to get to the next fun thing.

I'm one of the few that actually enjoys documenting things.

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Rob

No questions but I'm interested in how you go, that looks like a nice module.

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Rob

I just need to signal low voltage

Then use a supervisor chip or a comparator.

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Rob

latching relay or some clever work with FET or two.

I think Retrolefty had posted a good circuit using a relay before.

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Rob

Looking good.

5V 3A peak with up to 28V input.

How do you get 3A with such a small inductor?

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Rob

I'm curious how fragmentation of RAM is dealt with. It's probably more info than my brain will handle though.

It's not dealt with at all, so your brain should be able to handle the process

Typically in an embedded system you should malloc() only when configuring the program at the start and never again.

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Rob