Power up by extension header

Pins P9.5 and P9.6 are supposed to be connected to the DC power jack, as stated in the BBB System Reference Manual (figure 23, and explicit stated in page 113). So, I am using a external power supply at P9.1 ~ P9.2 as GND and P9.5 ~ P9.6 as +5V. The power led goes up but the board does not start to run and no other leds will blink. If I power up from DC jack or usb cable, everything goes as expected, so I ask if I am doing something wrong or should connect the other gnd pins. I double checked the connections and they are ok.


Not sure what you are doing wrong, hard to tell.

What is your power source?Is it grounded?

How much current can it supply?

Can you send a picture of your wiring?


Sorry for the delay, attached is a pdf with the schematic. I tried to take some pictures of my wiring and also to triple check the connections, but the lab was closed for fumigation.

Some other points are:
→ I am using both PRUs to read some encoders and generate four PWM signals (10bits @ 12KHz). In this schematic only the encoder inputs are complete.
→ I am powering this cape with a switched industrial grade power supply. When I power up the board from the DC jack I am using a cheap adapter (also switched).
→ If I power up from usb and after the board boot process I connect the power to the extension cape, then I can read one encoder (have not tested the others but they should).

Thank you,

Carlos Novaes

BasicCape.pdf (30.4 KB)

dont know why, but the pdf file does not open correctly on google docs. Some connectors are not displayed, although the connections to the BBB itself are perfect visible. Downloading and opening with a pdf viewer (okular, acrobat…) works perfectly.

Fount it.
In the circuit drawing I connected P9.10 (SYS_RESETn) to the gate of the transistor 2n7000, but in the universal board I connected P9.9 (PWR_BUT). Now the board is booting up every time.

Excellent! It is usually something simple.