Do not power BBB/BBG via USB?

Hello,

I have a BBB which is currently powered via USB and external power supply (and a similar BBG which is powered via USB and via external supply feed into VDD from connected cape).

Now when a user wants to do a full power cycle, all possible power sources have to be disconnected which can be somewhat complicated.

So my question: is there a possibility to disable power supply via USB? E.g. a soldering jumper which has to be opened? Or in case not - is there a possibility to permanently program the PMIC to not to power the board from USB?

Thanks!

If you cut that trace on a BBB, then the BBB won’t power itself up via USB.

BBB.png

Great - thanks! So there is no way to do that programmatically via PMIC?

I wasn’t able to find one. I believe it’s built in to the hardware of http://www.ti.com/lit/ds/symlink/tps65217.pdf
Feel free to review and see if you come to the same conclusion that I did!

Cheers,
Alex

The proper way is to modify the driver tps65217.c :

diff --git a/drivers/mfd/tps65217.c b/drivers/mfd/tps65217.c
index ca19130…a7ae900 100644
— a/drivers/mfd/tps65217.c
+++ b/drivers/mfd/tps65217.c
@@ -253,6 +253,7 @@ static int tps65217_probe(struct i2c_client *client,
bool status_off = false;
int irq = -1, irq_gpio = -1;
int ret;

  • bool usb_off = false;

node = client->dev.of_node;
if (node) {
@@ -265,7 +266,8 @@ static int tps65217_probe(struct i2c_client *client,
chip_id = (unsigned long)match->data;
status_off = of_property_read_bool(node,
“ti,pmic-shutdown-controller”);

Hello Micka,

is this permanent? Means does the PMIC know even after a power cycle to not to use USB power any more? As far as I understood the description of USB_EN in the PPATH register, this is reset to default values after power was turned off…

Thanks :slight_smile:

For my use case it’s perfect:

the board is powered by a cape. we disabled power from USB, because the cape is not made to be powered by the beagle.

and yes you are right, the PPATH is hard reset to 1.