# MKR NB 1500 Power Saving Mode

**URL:** <https://forum.arduino.cc/t/mkr-nb-1500-power-saving-mode/685250>\
**Category:** MKR NB 1500\
**Created:** [December 2, 2020, 7:43am UTC](https://forum.arduino.cc/t/mkr-nb-1500-power-saving-mode/685250 "2020-12-02T07:43:20Z")\
**Posts on this page:** 1\
**Showing post:** 5

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**Author:** ![zbelding](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/zbelding/32/238831_2.png) [@zbelding](https://forum.arduino.cc/u/zbelding)\
**Post date:** [December 3, 2020, 3:06pm UTC](https://forum.arduino.cc/t/mkr-nb-1500-power-saving-mode/685250/5 "2020-12-03T15:06:08Z")

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> ccorrads:  
> @zbelding Do you have exactly the implementation of pulsing the pwr\_on pin in Arduino?
> 
> From code examples....I'm guessing...
> 
> pinMode(SARA\_PWR\_ON, OUTPUT);  
> digitalWrite(SARA\_PWR\_ON, HIGH);  
> delay(150); // Datasheet says power-on pulse should be \>=150ms, \<=3200ms  
> digitalWrite(SARA\_PWR\_ON, LOW);
> 
> I'm noticing (as you and others have pointed out) that after random times, the SARA chip goes into an unresponsive state and my sketch basically infinitely loops in trying to reconnect via "nbAccess.begin()". I thought that the begin method in the NB class of the MKRNB library would pulse the pwr\_on pin correctly...but maybe I am mistaken?
> 
> I'm using the latest master branch of the MKRNB library since the fixes aren't in a release yet:  
> [MKRNB/src/NB.cpp at master · arduino-libraries/MKRNB · GitHub](https://github.com/arduino-libraries/MKRNB/blob/master/src/NB.cpp#L80)  
> then...  
> [MKRNB/src/Modem.cpp at master · arduino-libraries/MKRNB · GitHub](https://github.com/arduino-libraries/MKRNB/blob/master/src/Modem.cpp#L59)
> 
> I'm thinking maybe the V\_INT pin check after some time in Arduino is out of sync with the Modem's actual state and it infinitely hangs because it never actually sends the power on pulse when it gets into this unresponsive state.

Your pwr\_on code looks right to me. I usually use 500ms, but anything between the range you found in the manual should work. I would keep it less than 1.5s, that way you don't accidentally turn the modem off if it's already on. V\_INT is not connected on this board. It doesn't really need to be. You can pulse the pwr\_on pin at any time to confirm the modem is on.  
 ![](https://europe1.discourse-cdn.com/arduino/original/4X/7/8/c/78c771b8d9fc261831027dc632a21533efac45e1.png)  
Sorry, I can't help you too much with arduino library specific questions. I only used these libraries in the very beginning.  
With regard to the modem seeming to be unresponsive, in my experience this was completely fixed with the new version of the modem firmware. I believe this was a specific AT&T issue. You can find more details in my other threads.

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