Can the nRF52840 MCU power LED direct?

RE: Can the nRF52840 MCU power LED direct?

awneil — Thu, 25 Apr 2019 09:14:51 GMT

[quote userid="76921" url="~/f/nordic-q-a/44533/can-the-nrf52840-mcu-power-led-direct/183619"]Both GPIO codes don't work[/quote]

As with debugging any problem, you need to take this one step at a time.

For a start, have you tried using an unmodified SDK example on a DevKit? That is always the best place to start - giving you a known-good basis to work from.

In your circuit:

If you disconnect the LED cathode from the port pin, and ground it - does the LED light.
With the LED disconnected, can you see the pin level changing; eg, on a scope or meter?
Run you code in the debugger - is it actually reaching the point(s) that configure the pins, & change the output?

How To Debug

RE: Can the nRF52840 MCU power LED direct?

awneil — Thu, 25 Apr 2019 09:04:48 GMT

[quote userid="65515" url="~/f/nordic-q-a/44533/can-the-nrf52840-mcu-power-led-direct/183620"]P1.x pins do not have high drive capability (NRF_GPIO_PIN_H0D1), nor do some P0.x pins[/quote]

It was just a quick look, but I couldn't see that mentioned in the Product Specification ?

RE: Can the nRF52840 MCU power LED direct?

ctchong — Thu, 25 Apr 2019 08:09:50 GMT

I'm using P0.11 P0.12 P1.06 P1.07

All P1.x have no high drive capability?

Thank you

RE: Can the nRF52840 MCU power LED direct?

hmolesworth — Thu, 25 Apr 2019 04:39:05 GMT

Which pins are you using for led_pin and LED_1? P1.x pins do not have high drive capability (NRF_GPIO_PIN_H0D1), nor do some P0.x pins; this is sometimes overlooked .. Also be aware that if 3.3V is very much higher than your nRF52840 i/o voltage there may be issues with back-drive (phantom power) into the port pin.

RE: Can the nRF52840 MCU power LED direct?

ctchong — Thu, 25 Apr 2019 03:39:38 GMT

nrf_gpio_cfg_output(led_pin);
nrf_gpio_cfg(LED_1,NRF_GPIO_PIN_DIR_OUTPUT,
                NRF_GPIO_PIN_INPUT_DISCONNECT,
                NRF_GPIO_PIN_NOPULL,
                NRF_GPIO_PIN_H0D1,      
                NRF_GPIO_PIN_NOSENSE);
                
nrf_gpio_pin_write(led_pin, 0);
nrf_gpio_pin_write(LED_1,0);

I am connecting the LED like Figure 1: +V is 3.3V and PORT Pin is configured as LED_1 and led_pin. I have 2 LEDs configured as the same connection.

Both GPIO codes don't work.

Thank you

Best regards,

Chong

RE: Can the nRF52840 MCU power LED direct?

awneil — Wed, 24 Apr 2019 15:05:42 GMT

[quote userid="76921" url="~/f/nordic-q-a/44533/can-the-nrf52840-mcu-power-led-direct/183527"]How do you configure a GPIO to current sink? [/quote]

It's not about the GPIO configuration - it's how you connect the LED.

How to properly post source code:

RE: Can the nRF52840 MCU power LED direct?

ctchong — Wed, 24 Apr 2019 14:02:16 GMT

Hi,

How do you configure a GPIO to current sink?

I tried the following but it doesn't seem to work.

nrf_gpio_cfg(LED_1,NRF_GPIO_PIN_DIR_OUTPUT,
NRF_GPIO_PIN_INPUT_DISCONNECT,
NRF_GPIO_PIN_NOPULL,
NRF_GPIO_PIN_H0H1,
NRF_GPIO_PIN_NOSENSE);

nrf_gpio_pin_write(LED_1,0);

Thank you

Best regards,

Chong

RE: Can the nRF52840 MCU power LED direct?

ctchong — Fri, 08 Mar 2019 10:23:39 GMT

I have changed it to current sink. The mcu_photo_pos1 is connected to a gpio (adc) to read the voltage of the photo sensor.

Thank you

Best regards

Chong

RE: Can the nRF52840 MCU power LED direct?

awneil — Fri, 08 Mar 2019 08:48:14 GMT

That seems to have been copied from some other schematic?

So start by understanding how that other circuit works.

Electrically, the nRF GPIOs aren't much different from GPIOs on other microcontrollers - compare the nRF specification against the other microcontroller's documentation ...

EDIT

Note that I only said sinking is "generally better" - I didn't say that sourcing is impossible!

Your circuits don't seem to make much sense - how do you think they are supposed to work?

RE: Can the nRF52840 MCU power LED direct?

ctchong — Fri, 08 Mar 2019 03:28:46 GMT

I have 2 photo sensors. How do I do a current sinking circuit for this ? Thank you

RE: Can the nRF52840 MCU power LED direct?

awneil — Thu, 07 Mar 2019 10:15:46 GMT

The Product Specification tells you the current capabilities of the GPIO pins.

Take a look at the Dev Kit schematics for examples.

It's generally better to have a microcontroller GPIO switching to ground (ie, "sinking" the LED current)

https://startingelectronics.org/articles/current-sourcing-sinking/