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The first two versions of servo_v4 (red and blue) have the TPD2E001 ESD between VBUS and CC1/CC2. This part has a breakdown min voltage of 11V. Therefore for these versions of servo_v4, need to limit VBUS to less than the default 20V value. This CL adds support to read two board ID gpios attached to the gpio expansion part. The max VBUS voltage is limited to 9V for red/blue and allowed to be 20V for black. BUG=b:38351574 BRANCH=servo_v4 TEST=Manual Modified a servo_v4 to add the 2 new pullup resistors. Tested with this unit and with a unit that does not have the pullups. Verified that without the pullups the version ID reads a 0 and the max VBUS voltage that will be requested by the CHG port is 9V. Wih the modified servo_v4, verified that the version reads 3 and the CHG port will request up to 20V. Change-Id: Ic41fcbe3a5c000282552c7322b5ab18ebb203cd2 Signed-off-by: Scott Collyer <scollyer@google.com> Reviewed-on: https://chromium-review.googlesource.com/507027 Commit-Ready: Scott Collyer <scollyer@chromium.org> Tested-by: Scott Collyer <scollyer@chromium.org> Reviewed-by: Nick Sanders <nsanders@chromium.org>
For an overview of the Embedded Controller firmware, refer to http://www.chromium.org/chromium-os/2014-firmware-summit For instructions on building from source, refer to http://www.chromium.org/chromium-os/ec-development/getting-started-building-ec-images-quickly