# Boot sources missing on mangOH Yellow

**URL:** <https://mangoh.discourse.group/t/boot-sources-missing-on-mangoh-yellow/4243>\
**Category:** mangOH Yellow\
**Created:** [April 9, 2020, 2:54pm UTC](https://mangoh.discourse.group/t/boot-sources-missing-on-mangoh-yellow/4243 "2020-04-09T14:54:13Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![paulmeis](https://avatars.discourse-cdn.com/v4/letter/p/c57346/32.png) [@paulmeis](https://mangoh.discourse.group/u/paulmeis)\
**Post date:** [April 9, 2020, 2:54pm UTC](https://mangoh.discourse.group/t/boot-sources-missing-on-mangoh-yellow/4243/1 "2020-04-09T14:54:13Z")

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Hello,  
I am currently trying to use the accelerometer to wake the board from ULPM.  
I used the example code from the [ShakeNWake](https://github.com/mangOH/Demos/tree/master/ShakeNWake) demo and adapted the GPIO number to match the one used on mangOH Yellow (GPIO21).

However GPIO21 is not listed in the available boot sources of the board:

```bash
# ls /sys/module/swimcu_pm/boot_source/
adc clear enable gpio36 gpio38 timer

```

Yet GPIO21 is labeled as “Wakeable” in the [mangOH Yellow Schematic](https://mangoh.io/uploaded-documents/Reference/mangOH%20Yellow/Hardware/Schematics/mangoh_yellow_21.pdf).

Is it normal ? Can I add this GPIO as a boot source myself ?

Thank you for your time, have a good day !

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<div class="post-metadata">

**Author:** ![paulmeis](https://avatars.discourse-cdn.com/v4/letter/p/c57346/32.png) [@paulmeis](https://mangoh.discourse.group/u/paulmeis)\
**Post date:** [April 14, 2020, 8:56am UTC](https://mangoh.discourse.group/t/boot-sources-missing-on-mangoh-yellow/4243/2 "2020-04-14T08:56:11Z")

</div>

Okay I read the [wp77xx Technical Specification](https://source.sierrawireless.com/resources/airprime/hardware_specs_user_guides/airprime_wp77xx_product_technical_specification/#sthash.0HHYrTbc.5hVLgA0F.dpbs) and it says only GPIO 36 and GPIO38 are usable to wakeup from ULPM.  
GPIO21 can only wake the device from _Sleep State_.

I thought the _Sleep State_ was the same as _Low Power Mode_, but it’s not : the _Sleep State_ is a Low-Power active state which require the module to be fully powered.

But this means you can’t use the accelerometer interrupt to wakeup from ULPM on a mangOH Yellow without modifying the BMI160 driver ?  
Current driver configuration uses only the INT2 pin of the driver, which is linked to GPIO21 on mangOH Yellow…