I’ve connected a battery to TP_5-8. Seems to work fine. However when the BBB is shutdown, voltage remains at VDD_3V3EXP P9_3/4. I’ve read elsewhere this is a know issue, however a work around is discussed but I have to little information to implement it.
exert:
“connected U4 pin 1 (enable) back to VDD_3V3AUX (same as A5C). It now shuts down correctly while on battery”
Can someone comment on where “U4 pin 1” & “VDD_3V3AUX” are located?
Or any other solution to this issue.
Many thanks,
You need to check out the schematic for your version of the BBB to see the connections we’re discussing. And carefully look at the board to locate the parts we’re discussing. The mod is for Rev B & C boards with PCB Rev B6. It is essentially making the connection that was used on the A5C (and prior) versions based on the PCB Rev B4.
U4 is an 8 pin IC on the backside near the site of TP5-8. You need to gently unsolder and lift pin 1 so that it does not contact the pad that it was soldered to. Then solder a small wire (e.g. 30 gauge) to that pin and route to and solder to D1 (the PWR LED) on the top side on the end nearest R10 (the in-board end).
This is used as a backup power source if the main or USB power is removed on purpose or accidentally. The software can detect the change in power source and start the orderly shutdown. This results in the voltages going to (near) zero when shutdown is completed.