[Ovmsdev] OVMS Hardware v3.1

[Stephen Casner]

On Wed, 17 Jan 2018, Mark Webb-Johnson wrote:

> The only solution we can see is to continue to use GPIO22 for FL_CS2
> external flash, but use a level converter 3.3V -> 1.8V. We only need
> uni-directional, but it must operate fast enough not to interfere
> with a 40MHz SPI bus. Maybe a resistor voltage divider would be too
> slow / interfere too much, so safer to use a simple single channel
> uni-directional 3.3V->1.8V logic level shifter chip.

Just out of curiousity I looked in DigiKey to see what SMD
unidirectional level translators were available.  They all seem to
have typical propagation delays in the neighborhood of 5ns.  Since the
cycle time for 40MHz is 25ns, it seems like that delay would be a
problem.

                                                        -- Steve