How to implement RESET button on nRF51822?

[Michal Zacharias]

I would like to know how to implement reset button on nRF51822. Image of schematic would be very useful, but good explanation should be enough. Thank you in advance.

I already have SWDIO/nRESET (pin 23) connected from ARM programming connector.

[Håkon Alseth]

Hi,

You can connect a button from SWDIO/nRESET, which is active low (ie, tied to GND when pushed). When the MCU is in normal run mode, the SWDIO/nRESET pin can be used a normal reset input.

When you program the nRF-device, it will run in "debug mode" until you do a power cycle or do a pinreset from the debugger (cmd line: "nrfjprog --pinreset")

Best regards Håkon

[Michal Zacharias]

So SWDIO/nRESET has internal pullup? I don't need to add hardware pullup? Just line from SWDIO/nRESET to programming header and parallel to it I should put an active low reset button?

[Håkon Alseth]

Yes, that is correct. there's an internal pull up on that pin.

-H

[Michal Zacharias]

Thank you :)

[William Grange]

Hi Håkon,

I was planning to use an active-low reset switch in parallel to SWDIO just like Michal describes. The -EK shows 150Ω in series with the switch to ground.

Is the value of the pull-up 13kΩ similar to the GPIO?

Also, can you comment on whether there is an internal capacitor to GND on the reset line or a Schmidt trigger on the reset line's input to de-glitch the transitions?

Thanks, William