Hi guys!
I want to power NiclaVision not with a battery, but with external 5V power supply.
I also want 5V on its digital outputs.
Can I simply supply 5V as per drawing below?
This “the buck convertor must be shut down” in specs confuses me - how do I shut it down?
Thanks everyone!
Hi, You can give it VIN of 5V. That is safe. The level shifters on the board also support up to 5V. But, as it says you need to shutdown that buck converter.
We don’t have any software directly to do this. However, you just need to talk to the PMIC onboard. This is on the I2C2 bus which is the same bus used for external I2C.
from pyb import I2C
i2c = I2C(2, I2C.MASTER)
print(i2c.scan())
[8, 41, 54]
PF1550, Power management integrated circuit (PMIC) for low power application - Data sheet (nxp.com)
Looks like you want to turn off SW2 by writing 0x0 to register 0x3b.
E.g.
from pyb import I2C
i2c = I2C(2, I2C.MASTER)
print(i2c.scan())
i2c.send("\x3b\x80", addr=0x8)
And I confirmed this turned it off.
Do:
i2c.send("\x3b\x0f", addr=0x8)
To turn it back on.
Note the 0x80. That last bit must be set as it controls the regulator discharge. If that’s 0 then when you apply 5V the regulator will short whatever voltage you are applying to ground.
Thanks @kwagyeman !
This is really detailed reply.
However let me clarify one thing.
Suppose I connect +5v to VDDIO_EXT without turning off SW2.
(Suppose card has not been flashed, or I have error in my code or something).
What happens then?
Will it kill the board? Or is it just sub-optimal way of doing things?
Will peripherals still be driven by 5v?
Mmm,
So, I looked at the datasheet more carefully and the maximum voltage on the SW2FB is 3.6V. So, applying 5V will break the PMIC.
Yeah, don’t try to apply 5V for the level shifters. This will absolutely damage the device.
You can probably force it for values of 1.8V to 3.6V. That said, since you’d need to prevent it from turning on when you boot it will be really hard to make this work.
Thanks @kwagyeman !
This was very helpful.
