SPI bus length?

Started by Tom Becker July 13, 2006
I have a dilemma: I need a fast compass in a complex motorized device
but the motor magnets (which move within the project as the project
moves over Earth) disturb the compass in a complex manner that would, I
expect, be very difficult to correct. I plan on mounting the compass on
an arm that would remove it from the motors.

The CMPS03 uses I2C; the V2Xe uses SPI. It appears that I2C signalling
can run some appreciable distance and should not be problematic over a
few feet, and I expect that slow, bit-banged SPI would be similar over
the same run. But what about the processor SPI bus? How much wire can
hang on it before the processor starts coughing?

> ... How much wire...

Answering myself, not much, apparently. I couldn't get a machine to
run with 14" of SPI bus on it. I'll need to use bit-banged SPI with
the V2Xe.