GPIO Sinking Resistance

[edwardsbobg]

I am powering an LED / current limiting resistor by sinking current into an IO pin. Where can I find the resistance of the IOs when sinking current?

[RK]

oh and one other calculation you can do - check the spec sheet for the current at which the max output for a 'low' is. I seem to remember they spec it at 0.5mA but I'm not sure. You can work that back to the max static resistance the pin could have. Personally I've always had lows be very close to zero on all the Nordic products I've worked with, but it is within spec to have a static resistance on the pin. If you really want to know, put in a higher value resistor and short out the LED and see what measurements you get at a low current like 0.5mA, that will tell you if the GPIO does have noticeable static resistance. 

[Turbo J]

Did you remember to put the pin into high drive mode?

Standard drive is only about 4 mA, explaining your high voltage drop.

[Bselekar]

Hi,

In our new project we have 8 signal LED diodes attached to nrf52832, they are all sinking current:

• 3x GREEN 0.8mA (P0.16, P0.17, P0.18)
• 1x RED 3.3mA (P0.19)
• 4 x BLUE 1.3m (P0.20, P0.25, P0.26, P0.27)

In total, this is approximately 11mA. Does anybody see any risk on operation of nrf52832 in case all 8 LED diodes are turned ON?

I don't know how the pins are connected to the common GND to maybe divide LEDs?

Thank you for your comment, 

Regards, 

Blaz