Hello,
Background:
BeagleBone Black is a brand new platform to us in our Embedded System course here, which is just applied into use about 2 months ago. Recently, we have 5 boards that are experiencing power issues, where the LED flashes and the board does not power up. There are short circuits between VDD_CORE or VDD_3V3A and GND.
We found out that there is a note in the BBBlack System Reference Manual, which says:
"NOTE: DO NOT APPLY VOLTAGE TO ANY I/O PIN WHEN POWER IS NOT SUPPLIED TO THE BOARD. IT WILL DAMAGE THE PROCESSOR AND VOID THE WARRANTY.
NO PINS ARE TO BE DRIVEN UNTIL AFTER THE SYS_RESET LINE GOES HIGH."
And the official wiki of BBBlack (http://www.elinux.org/Beagleboard:BeagleBoneBlack#Improper_Power_Down....All_Revisions) mentions:
"We have been chasing this for a while now and due to the small number of boards that have the issue and the fact that the issue can also be caused by having things connected to IO pins not powered correctly, it has been hard to nail down. Our initial take was that it was a manufacturing issue on some boards, but we could never prove that. Based on the latest information we have gathered, this appears to be an instance where the PMIC does not power down the processor in the right order due to the violent removal of the power cables, either USB or DC. So, we are recommending that the power button be used to power off the board or by issuing the Halt command. After that you can remove the power cable. If everyone follows this process, we should see a decrease in these issues, but it will take a while for the results, either good or bad, to show up. This will also help prevent the contamination of the eMMC and the SD cards by allowing the kernel to shutdown properly before power is removed."
Though we have called RMA, the real cause of the issue is still unknown. We need to know it to avoid more damage.
Furthermore, if it really happens with the circumstance noted in the SRM, the power booting sequence of sensors or other devices and the BBB board would be fairly important in a battery supply system such as a intelligent car or a quadcopter, which is also a bit hard to design.
So here comes the questions:
Questions:
1) Though "it has been hard to nail down", is there any documents indicate the note above? How does it happens? Or is it not associated with the processor?
2) In my opinion, considering the note, all the devices in such a system have to remain unpowered until the BBB is booted. Is it true? And any advice?
Thanks.
