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Kernel notes (sunshout)
Kernel notes (sunshout)

Posted on Originally published at sunshout.tistory.com

Pi Zero + MPU-9250: empty i2cdetect is a 3.3V problem, not a Python library

#raspberrypi #python #i2c #embedded

I keep seeing Pi Zero + MPU-9250 threads where SDA/SCL look right and i2cdetect is empty — or the GPIO dies after a 5V VCC.

Pi GPIO is 3.3V tolerant. Even if the breakout has a regulator, feed VCC from Pin 1 (3.3V), not Pin 2/4 (5V), unless you have confirmed the I2C lines are shifted.

Full pin table and photos (Korean):

https://sunshout.tistory.com/2204

Wiring that actually enumerates

MPU-9250 Pi Zero Physical
VCC 3.3V Pin 1
GND GND Pin 6
SDA GPIO2 / SDA1 Pin 3
SCL GPIO3 / SCL1 Pin 5

Leave EDA/ECL/AD0/INT alone for a first bring-up.

Then:

sudo raspi-config   # Interface Options → I2C → Enable
sudo reboot
sudo apt install -y i2c-tools
i2cdetect -y 1
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You want 0x68. The AK8963 mag on the same package may also show 0x0c.

How to read the grid

  • Empty bus: power, Dupont, or I2C not enabled. Almost never smbus / Python.
  • 0x69: AD0 is high. Either tie AD0 to GND or use 0x69 in software.
  • UU: a kernel driver already claimed the address. Unload it before userspace.
  • 0x68 present, values garbage: supply ripple or a 5V-fed module with unshifted SDA. Check 3.3V at the module under load. A random LM2596 next to a VTX will do this — I use a UBEC for companion Pi power (notes).

If you wanted fused quaternions without running a Kalman filter on the Zero, that is a different part (BNO085, SH-2 on the package): https://sunshout.tistory.com/2205

I do not want the Pi doing fusion while it is also a flight-controller companion.

If your grid shows UU or 0x69, say which — those two are different bugs.

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