On Sun, Apr 20, 2014 at 01:54:53AM +0200, Ruben J=F6nsson wrote:
> You can also use a bidirectional level shifter based on a mos fet
> transistor and two resistors.

I'm familiar with this method.  We use it on the OLPC XO laptop, where
we have a slew of different power domain voltages.  Sometimes the
resistors are internal pullups.

http://wiki.laptop.org/images/a/ad/XO_4_Schematics.pdf

On page 5 is the first use, interfacing a 3.3V SPI FLASH ROM to GPIOs
on the SoC that are in the 1.8V power domain.  Meant we could use the
same field service tools.

Another on page 24, interfacing a 2.8V camera module I2C.

Another on page 26, interfacing the 3.3V MSP430 BSL serial programming
path of the touchscreen controller to 1.8V domain of the SoC.

Another on page 27, interfacing HDMI connector signals to the 1.8V
domain.

--=20
James Cameron
http://quozl.linux.org.au/
--=20
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