Update Power_capabilities.md

Author: chipguyhere

docs/Power_capabilities.md

@@ -16,14 +16,21 @@ that can be accessed on the I2C bus at address 0x75.  Access is possible via M5.
 - **Can it tell if it is running on external versus battery power?** If `isCharging()` or `isChargeFull()` true, probably on external power.
 - **Can it detect the rate of charge or discharge?** *probably not, but inference can probably be made by comparing `isChargeFull()` to the charge full current cutoff*
 - **Can it tell if a battery is present or absent?** *possibly, but not formally... an absent battery seems to always be reported as "charging", having a level of "100%", and never becomes "charge full"*
-- **Can it tell the state of charge of the battery?** Yes, using `getBatteryLevel()`, which returns one of: 0, 25, 50, 75, 100 (representing a percentage), or -1 (if unable to read)
+- **Can it tell the state of charge of the battery?** Yes, using `getBatteryLevel()`, which returns one of:
+    0, 25, 50, 75, 100 (representing a percentage), or -1 (if unable to read)
 - **Can it read its battery voltage?** Not possible to read the voltage level directly, only the approximate percentage of 0/25/50/75/100.
 - **Can communication with the IP5306 power controller be tested and confirmed?** Yes, with `canControl()`
+- **Where does the IP5306 power controller get its own power?** Only from either the battery or the USB port.  The 5V connection on the M5Stack
+    Core/Basic/Gray controller is not a power *source* for the IP5306 chip and is considered downstream from the chip (i.e. the *output*).  If the M5Stack controller
+    is being powered through the 5V pin (for example, through a base or some other accessory), this power is not an *input* to the IP5306 chip,
+    and will not charge the battery.  The IP5306 will shut down under this condition to minimize battery drain, unless configured not to. 
+    When the chip is shut down, it will not respond to I2C communication
+    (for example, `getBatteryLevel()` will return -1)
 - **What other capabilities?** *(to be answered -- translation of Chinese-language datasheet is difficult to understand)*
   - *auto shutoff settings - voltage low for how long causes a shutoff*
   - *inhibit the power button, report it as an event?*
   - *setting the charging voltage and current*
   - *distinguish between a software/hardware/watchdog/sleep/poweron reset*
   - *maintain any of the settings across power cycles and/or complete loss of all power*
   - *how does setAutoBootOnLoad() work? when enabled, it seems the device can be powered back on simply by connecting a load -- such as
-     connecting another M5Stack controller to be powered from PORTA -- if done before the shutdown_8s time expires*
+     connecting another M5Stack controller to be powered from PORT_A -- if done before the shutdown_8s time expires*