# Dev Team: Known Issues

**URL:** <https://community.zymbit.com/t/dev-team-known-issues/996>\
**Category:** ZYMKEY4\
**Created:** [October 30, 2020, 7:12pm UTC](https://community.zymbit.com/t/dev-team-known-issues/996 "2020-10-30T19:12:25Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Eric\_of\_Zymbit](https://avatars.discourse-cdn.com/v4/letter/e/c68b51/32.png) [@Eric\_of\_Zymbit](https://community.zymbit.com/u/Eric_of_Zymbit)\
**Post date:** [October 30, 2020, 7:12pm UTC](https://community.zymbit.com/t/dev-team-known-issues/996/1 "2020-10-30T19:12:25Z")

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- These are our current known issues on the zymkey 4.
- We will be doing our utmost to fix these issues in future patches and updates.
- If you don’t see your problem here, please refer to our FAQ topic [here.](https://community.zymbit.com/t/faq-zymkey-4i/823)

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<div class="post-metadata">

**Author:** ![Eric\_of\_Zymbit](https://avatars.discourse-cdn.com/v4/letter/e/c68b51/32.png) [@Eric\_of\_Zymbit](https://community.zymbit.com/u/Eric_of_Zymbit)\
**Post date:** [October 30, 2020, 7:17pm UTC](https://community.zymbit.com/t/dev-team-known-issues/996/2 "2020-10-30T19:17:00Z")

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<div class="post-metadata">

**Author:** ![Eric\_of\_Zymbit](https://avatars.discourse-cdn.com/v4/letter/e/c68b51/32.png) [@Eric\_of\_Zymbit](https://community.zymbit.com/u/Eric_of_Zymbit)\
**Post date:** [October 30, 2020, 11:16pm UTC](https://community.zymbit.com/t/dev-team-known-issues/996/3 "2020-10-30T23:16:45Z")

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**Issue: Cpu Scaling Governor**

**Issue Description:**  
We have seen some issues with the scaling cpu governor on the raspberry pi interfere with the i2c bus. This sometimes causes the zymkey to be put into a odd state or return failures from operations that get optimized out by the governor.

**Workaround Solution We Recommend!**  
The raspberry pi sets the **scaling governor** to be “ **ondemand** ” by default. We recommend switching this mode to “ **performance** ” to get the best out of the zymkey.

**Be warned this will drain more battery power when switched to “performance”!**

**Set to performance but not persistent on reboot:**

1. Run as root: sudo su
2. echo performance \> /sys/devices/system/cpu/cpufreq/policy0/scaling\_governor

**Set performance to be persistent on reboot with a systemd service:**

1. Create a .service file in /etc/systemd/system/
2. **Write this code to .service file:**

> [Unit]  
> Description=Set scaling governor to performance  
> After=multi-user.target  
> Before=zkbootrtc.service  
> [Service]  
> Type=oneshot  
> ExecStart=/bin/sh -c “echo performance \> /sys/devices/system/cpu/cpufreq/policy0/scaling\_governor”  
> [Install]  
> WantedBy=multi-user.target

1. Enable the service: sudo systemctl enable yourservice
2. Start the service: sudo systemctl start yourservice