Working Paul McWhorter’s series with the AI fusion hat. While working in PWMs out, I get the following error: OSError: Fusion HAT not connected, check if Fusion Hat is powered on. The line of python which triggers it is: redLED= PWM(redPin). RGB LED is ON all the time (all three colors)…have to remove physical connection to turn off, even when Hat/Pi are shut down. I was able to use digital out pins successfully. All lights are ‘on’ on the hat, successfully zero’d servos, …seems to function otherwise so far as I have ran it. Any suggestions? Thanks!
There are two possibilities for this error report:
- The Raspberry Pi is powered on, but the Fusion HAT is not powered:
I have attached a photo of the setup during normal operation. Please check if your wiring and LED indicators match mine. If the issue persists, please take a photo (preferably from the same angle) and send it to us.
- I2C on the Raspberry Pi is not enabled:
Run the following commands in the terminal:
sudo raspi-config
Then navigate to: 3 Interface Options → I5 I2C → Yes to enable I2C. After enabling I2C, try running the example again.
I’m having exactly the same problem at exactly the same point in PW tutorial (i.e code for digital pin works ok put code for PMW throws up error that fusion board is not connected.
Are you are using a raspberry 4 for the tutorial?
I have the same problem. I get a single LED to blink as Paul McW. but no PWM works
Yeah, at one point all three led’s of the rgb led lit up, but had the same error. I powered everything down and rebooted and restarted. Same error, no led now. I presented this problem to our future IA overlords (Claude), and it thinks the pi kernel is wrong and it wants to rebuild it. Because Paul warns about not altering things, I’ve bee reluctant to let Claude update it. Let’s hope the Sunfounder folks can help us out!
We followed Paul’s tutorial but were unable to reproduce the issue you encountered. Could you please run the following commands to help us check your Raspberry Pi system, kernel, and whether the Fusion HAT driver has been loaded successfully?
uname -a
cat /etc/os-release
i2cdetect -y 1
dmesg | grep fusion_hat
lsmod | grep fusion_hat
ls /sys/class/fusion_hat/fusion_hat
Under BUG REPORT URL I had to omit the third URL as the forum wouldn’t let me post three urls.
pi@ai-fusion:~ $ uname -a
Linux ai-fusion 6.12.75+rpt-rpi-2712 #1 SMP PREEMPT Debian 1:6.12.75-1+rpt1~bookworm (2026-03-11) aarch64 GNU/Linux
pi@ai-fusion:~ $ cat /etc/os-release
PRETTY_NAME=“Debian GNU/Linux 12 (bookworm)”
NAME=“Debian GNU/Linux”
VERSION_ID=“12”
VERSION=“12 (bookworm)”
VERSION_CODENAME=bookworm
ID=debian
HOME_URL=“https://www.debian.org/”
SUPPORT_URL=" Debian -- User Support "
BUG_REPORT_URL=
pi@ai-fusion:~ $ i2cdetect -y 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: – – – – – – – –
10: – – – – – – – 17 – – – – – – – –
20: – – – – – – – – – – – – – – – –
30: – – – – – – – – – – – – – – – –
40: – – – – – – – – – – – – – – – –
50: – – – – – – – – – – – – – – – –
60: – – – – – – – – – – – – – – – –
70: – – – – – – – –
pi@ai-fusion:~ $
pi@ai-fusion:~ $ dmesg | grep fusion_hat
pi@ai-fusion:~ $ lsmod | grep fusion_hat
pi@ai-fusion:~ $ ls /sys/class/fusion_hat/fusion_hat
ls: cannot access ‘/sys/class/fusion_hat/fusion_hat’: No such file or directory
pi@ai-fusion:~ $
how can I reply to the suggestion to run several commands
that’s exactly the same response that I get when I run the code (except I ran with img :bookworm (2025-09-16).
I also get sae issues when flashed with latest img on Sunfounder site
Thank you very much for providing the kernel information. This aligns with what we suspected — it appears that you manually updated the system and upgraded the kernel, which caused the Fusion HAT driver to disappear.
Our default system kernel is Linux ai-fusion 6.12.47+rpt-rpi-2712. We manually upgraded the kernel to Linux ai-fusion 6.12.75+rpt-rpi-2712 and were able to reproduce the issue.
Please try reinstalling the Fusion HAT driver using the following commands:
cd ~/fusion-hat/driver/
make
sudo make install
Alternatively, if you prefer not to make too many changes manually, you can reinstall the system image we provide.
Thank you again for the information. We will add this issue to the FAQ section of our documentation.
This solved the problem on my RaPi4.
But…
Although I was prompted that UPDATES WERE AVAILABLE - i DID NOT INSTALL them!
So I’m not sure how KERNEL disappeared/became corrupted
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That worked. Thank you!
Your message indicated that I changed the software. I did not. I followed the Sunfounder instructions. When I encountered the error in the lesson I consulted Claude. I only suspected the kernal because I asked Claude, and it prompted me to input the same diagnostic inputs as you provided. When Claude suggested rebuilding is when I came to the forum as I didn’t want to alter anything. It seems that others are experiencing the same issue. Thanks for the fix.
I tried the above and get "bash: cd~/fusion-hat/driver/: No such file or directory.
This was after I went to the Sunfounder site and downloaded the software on a new 128gb sd card (ai.fusion.lab.kit-0.1.0.img). I still get the error Fusion HAT not connected. The digital pins work but that is all.
After you flashed the ai.fusion.lab.kit-0.1.0.img image and received the “Fusion HAT not connected” error, please try running the following commands to see if it resolves the issue:
cd ~/fusion-hat/driver/
make
sudo make install
This driver source should definitely be present in that image. Let me know if the error persists after running these commands.