The project changed as various engineers reported concerns, both potential
and actual. Instead of one huge board there are now four relatively small
boards, two at the top and two at the bottom. Top-to-bottom comms is a
logical extension of the CAN bus, whilst the I2C bus will run the width of
each board, a distance that doesn't give me any cause for concern, either
in terms of signal length or physical length. So thank you for your
suggestions, but to my relief the potential problem has gone away.
The project is a larger version of a product that has already been built,
and that did use one large board that took the I2C over a significant
length. I used 0.4 mm track width, and all was OK, though being a
demonstrator it hasn't been through environmental testing. So maybe the
roasting is yet to come, both for the board and for myself :)
I wouldn't want to run SPI over anything other than a short distance, as
that would be begging for trouble IMHO. I have in the past run I2C over
many metres of cable with no special drivers (just carefully designed
filtering), but it was only low speed.
Regards,
Robert.
