How to use GPIO pins on 3.3V ?

[shockline]

I am trying to communicate with PN7150 from nRF52840 DK using I2C pins.

PN7150 needs 3.3V and nRF52840 is supplying 2.9V.

I am able to read PN7150 on Arduino Mega but I fail when trying to read through nRF52840.

I believe the problem is due to nRF52840 supplying less than 3.3V.

How can I change output voltage on nRF52840 DK ?

Thank You

[awneil]

shockline said:

I believe the problem is due to nRF52840 supplying less than 3.3V

That's possible, but I'd have thought that 2.9 should generally be close enough to 3.3 for most cases.

What have you done to confirm that it is actually the low voltage that's causing the problem(s) ?

[shockline]

I tried scanning PN7150 on Arduino Mega supplying voltage through Arduino's 3.3V pin. Everything worked fine.

I tried scanning other devices on nRF52840 such as SSD1306 OLED. They also showed up fine.

For some reason I am having trouble scanning for PN7150.

[awneil]

The nRF52840 absolute maximum voltage on an IO pin is VDD + 0.3V

https://infocenter.nordicsemi.com/topic/ps_nrf52840/abs_max_ratings.html?cp=3_0_0_8

So, if your VDD is 2.9V, that's 3.2V max.

Since I2C is open-drain, you could disconnect the pullups from the DK's VDD, and pull up to 3.2V instead.

It might be easier to use different pins - rather than try to remove pullups ...

[KevinL]

I think it's actually possible by using the nRF52840 in high voltage mode and changing the UICR REGOUT0 register to output 3,3 V on VDD. This changes all GPIO ports to 3,3 V.

infocenter.nordicsemi.com/index.jsp

[awneil]

Good thought ...

Although the REG0 is a buck regulator - so can't step up if the DK is only giving it <3.3V

https://infocenter.nordicsemi.com/topic/ps_nrf52840/power.html?cp=3_0_0_4_2_0_0#unique_1782262349

You'd also have to check carefully that it won't affect (or be affected by) anything else on the board ...

[awneil]

awneil said:

You'd also have to check carefully that it won't affect (or be affected by) anything else on the board

also applies to my earlier suggestion, of course.

[BinderT]

You can try setting the drive strength of the pin. Worked for me in some cases with spi.
https://devzone.nordicsemi.com/f/nordic-q-a/45247/spi-communication-problem/178753#178753

Best thing would be to hook-up a scope an see what going on. Another thing to try is to bit-bang the chip and see if you get a response as a control. 

awneil said:

Although the REG0 is a buck regulator - so can't step up if the DK is only giving it <3.3V

You can set the GPIO voltage to VDD by doing the following after flashing your application.
nrfjprog -f nrf52 --memwr 0x10001304 --val 0x00000005

Will only do this a an absolute last resort.

NOTE: The chip needs a full erase if you want to flash it again.

shockline said:

I tried scanning PN7150 on Arduino Mega supplying voltage through Arduino's 3.3V pin.

I am assuming the PN7150 is supply from 3.3V with the nrf. 5V is not going to work.