nrf52 GPIO sink & source current

RE: nrf52 GPIO sink & source current

Roger Clark — Sun, 20 Aug 2017 23:22:27 GMT

Unless you get a response from Nordic contradicting their own spec, you would have to assume that the max current is the total of both current supplied and sinked.

Both of these would probably cause the same amount of internal heating, which is probably why there is a limit

RE: nrf52 GPIO sink & source current

dingari — Sat, 19 Aug 2017 10:04:14 GMT

Which leads to the original question. If I source current through a pin and sink it through another pin, does that take twice the current from the max GPIO current?

RE: nrf52 GPIO sink & source current

Roger Clark — Sat, 19 Aug 2017 01:06:21 GMT

Well, just arrange your software to keep track of how many LED's its turned on and don't exceed the max current for the whole MCU and the individual pin current.

RE: nrf52 GPIO sink & source current

dingari — Fri, 18 Aug 2017 15:27:16 GMT

It's not really intended to work like a standard matrix display, simply an array of LEDs which can indicate different things. All LEDs will never be lit at the same time, at most a single column (wired intelligently, only a single LED is on at any given moment). Considering I've got some low-power SMD LEDs visible in broad daylight at ~1mA, the more and more I think this won't be a problem. I'll have to do some tests though.

RE: nrf52 GPIO sink & source current

Roger Clark — Fri, 18 Aug 2017 01:09:16 GMT

Yes. They are larger and far more expensive.

Perhaps you can find some sort of LED matrix device which has the LEDs and drivers built it, as you won't be able to drive all the LEDS directly from an nRF5x MCU as they cant supply the necessary current, and still have the LED's visible under normal lighting conditions.

Re:Sincing vs sourcing current

Its because there are more GND pins on the MCU package than Vcc pins.

Though in your case, you simply can't drive that many leds with only 15mA

Perhaps you should consider using a small OLED screen instead of LEDs

RE: nrf52 GPIO sink & source current

dingari — Thu, 17 Aug 2017 08:26:14 GMT

@Roger Clark, I've not considered addressable LEDs that much, since they are just a bit too large (typically 2-3mm wide). I'm aiming at 0603 (1.6mm wide) or even 0404 (1mm wide) LEDs to fit them into the volume of the product.

RE: nrf52 GPIO sink & source current

Roger Clark — Wed, 16 Aug 2017 22:40:21 GMT

Have you considered using addressable LEDs aka Neopixels