The red light on the MCU is turned on
by the BITalino firmware when the input value on pin A6 is bellow a programable threshold:http://forum.bitalino.com/viewtopic.php?f=9&t=43#p54
In normal conditions, for that LED to be on, one of three things should be happening
1) ABAT pin on the power block not connected to A6
2) ABAT pin always has a voltage always bellow 1.7V (which may be indicative of a faulty battery or a faulty component on the voltage divider circuit connected to the battery to provide the ABAT pin)
3) The device is being controlled directly (e.g. by the API), and the low battery indicator activation threshold is being set to a very low number using the battery(…)
method (e.g. http://bitalino.com/pyAPI/#bitalino.BITalino.battery
)NOTE THAT ON THE BITalino Plugged
, by default ABAT is disconnected from the A6 channel in order to enable the use of A6 for sensor connection, reason for which the low battery LED will always be on.
If you want to use A6 for low battery indication on the BITalino Plugged, you can shunt the two pads to the right of the JST connector on the PWR block, but be careful not to connect any sensor to A6 afterwards.
Currently you can use A6 for low battery or for sensor connection but not for both. This is something that will be changed in our BITalino (r)evolution device, to be launched later this year, and which will have an extra channel dedicated for the battery .
The BITalino Team