Hi Marek,
On 22/01/15 10:27, Marek Vasut wrote:
On Wednesday, January 21, 2015 at 12:55:15 PM, Graeme Russ wrote:
Section 4.1.2 of Freescale Application Note AN4199 describes the configuration required to operate the mx28 from a 5V source without a battery. This patch implements the changes to the Freescale bootlets which allow this configuration to properly boot the mx28 processor
Signed-off-by: Graeme Russ gruss@tss-engineering.com
I have to admit I don't really like this boatload of new ifdeffery. Isn't it possible to detect if the battery is or isn't connected at runtime ?
I doubt it. If you look at the circuit in AN4199, the BATTERY and DCDC_BATT pins are hooked up to VDD4P2 via 1k resistors. What the mx28 does internally is measure the voltages on the VDD5V and either BATTERY/DCDC_BATT pins and decides which to use (preferencing the battery unless it goes below a threshold).
Without this patch, the mx28 sees a good battery voltage and switches to battery mode which is drawn of DCDC4P2 which is now trying to be driven by the battery input which, of course, will not work.
So the only way to figure it out at runtime would be to have the battery inputs at 0v so you could see there is no battery.
The only other option would be to use a GPIO pin
Regards,
Graeme