How to use GPIO pins on 3.3V ?

RE: How to use GPIO pins on 3.3V ?

BinderT — Wed, 31 Jul 2019 15:17:41 GMT

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.

[quote userid="6462" url="~/f/nordic-q-a/50466/how-to-use-gpio-pins-on-3-3v/201624"]Although the REG0 is a buck regulator - so can't step up if the DK is only giving it <3.3V[/quote]

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.

[quote userid="82168" url="~/f/nordic-q-a/50466/how-to-use-gpio-pins-on-3-3v/201591"]I tried scanning PN7150 on Arduino Mega supplying voltage through Arduino's 3.3V pin.[/quote]

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

RE: How to use GPIO pins on 3.3V ?

awneil — Wed, 31 Jul 2019 13:39:43 GMT

[quote userid="6462" url="~/f/nordic-q-a/50466/how-to-use-gpio-pins-on-3-3v/201624"]You'd also have to check carefully that it won't affect (or be affected by) anything else on the board[/quote]

also applies to my earlier suggestion, of course.

RE: How to use GPIO pins on 3.3V ?

awneil — Wed, 31 Jul 2019 13:38:18 GMT

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 ...

RE: How to use GPIO pins on 3.3V ?

KevinL — Wed, 31 Jul 2019 13:32:43 GMT

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

RE: How to use GPIO pins on 3.3V ?

awneil — Wed, 31 Jul 2019 13:30:16 GMT

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 ...

RE: How to use GPIO pins on 3.3V ?

awneil — Wed, 31 Jul 2019 13:22:51 GMT

[quote userid="82168" url="~/f/nordic-q-a/50466/how-to-use-gpio-pins-on-3-3v/201608"]I was wondering if there was a method to increase the output voltage on nRF52840 DK with help of some code ?[/quote]

No - that'll be a hardware change.

RE: How to use GPIO pins on 3.3V ?

shockline — Wed, 31 Jul 2019 13:18:37 GMT

I don't have access to an oscilloscope. I am currently reading User Guide and Schematics.

I was wondering if there was a method to increase the output voltage on nRF52840 DK with help of some code ? Maybe I can try that first before moving to other options.

RE: How to use GPIO pins on 3.3V ?

awneil — Wed, 31 Jul 2019 13:03:02 GMT

Still not entirely conclusive that it's the voltage.

Have you looked at the lines with an oscilloscope to see what's going on?

Check out the nRF52840 Product Specification for details of its power supply restrictions & requirements.

Check out the nRF52840 DK User Guide and Schematics for details of the power supply arrangements on the board.

I2C voltage translators are available ...

RE: How to use GPIO pins on 3.3V ?

shockline — Wed, 31 Jul 2019 13:00:21 GMT

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.

RE: How to use GPIO pins on 3.3V ?

awneil — Wed, 31 Jul 2019 12:55:50 GMT

[quote userid="82168" url="~/f/nordic-q-a/50466/how-to-use-gpio-pins-on-3-3v"]I believe the problem is due to nRF52840 supplying less than 3.3V[/quote]

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) ?