In part one of this series I showed how to implement the “Power Key” to safely power up and shutdown the Beaglebone platform under Windows Embedded Compact 2013 or Windows Compact 7. To continue on the power management theme I will show how to implement the battery driver but first there are some hardware issues we need to take care of. It seems the hardware designers of the Beaglebone were thinking ahead in that they brought out all the needed connections to the PMIC (Power Management Integrated Circuit) for battery backed operation. The needed connections are shown as test points in this partial schematic: The full schematic is freely available from the BeagleBoard web site. The data sheet for the Texas Instruments PMIC is also available for download. As I have stated in my previous post, the TPS65217C PMIC has an integrated battery charger on board. In my case I am using a 1.75A/hr. Lithium-Ion (Li-ion) battery. A couple of the connections are quite obvious, Battery plus needs to go to TP5, Batt ...

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One thing I see often on poorly designed embedded systems is lack of a robust system wide power supply design. Quite often little thought is put in before hand on requirements for proper power sequencing. This is the fault of the system engineer who should understand all the issues but whom usually ends up pointing the finger for a faulty system at the hardware or software designer. And while the hardware issues can be obvious, things like out of spec regulators or switching power supplies that don't switch etc. some of the software issues can be much more subtle harder to detect. One that I have seen quite often is absolutely no regard for properly shutting down the system. Many times there is an off switch which kills all power but without ever informing the processor or OS ahead of time. Another design may force a reset on the processor and then power is cut. While the second example may be argued as preferred, both are examples of poor design.You may think that forcing a re ...

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