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Built-in project · ESP32-DevKitC V4

MicroPython MPU6050 accelerometer and gyroscope on an ESP32-DevKitC V4

MicroPython on an ESP32: machine.I2C on GPIO 14 and 13 reads an MPU6050’s acceleration and rotation, raw and in g and degrees per second. The whole build, an ESP32-DevKitC V4 and 1 more part, runs here in your browser on the firmware below; open it in the editor to change the wiring or the code and run it again.

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Intermediate About 20 minutes to build and run. Runs in your browser. Free, and no account needed.

The parts retail for about $12.50. On Mokxi they're free.

MicroPython MPU6050 accelerometer and gyroscope · ESP32-DevKitC V4live0.000 s 0.00x
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The circuit itself, running here on the simulator. Press what can be pressed; click anything else to open it in the editor.

What you'll learn

  • How the I2C bus uses two wires
  • Waking a sensor by writing to a register
  • Reading several values in one transfer
  • Raw sensor counts versus real units
  • Difficulty: Intermediate
  • Time: About 20 minutes
  • Board: ESP32-DevKitC V4
  • Parts: 3

How it works

The MPU6050 talks over I2C, a two-wire bus. SCL goes to GPIO 14 and SDA to GPIO 13, at 400 kHz. The chip's address is 0x68. At power-up it sleeps, so the program first writes zero to a register to wake it up.

Then, once a second, the program reads 14 bytes in one go: acceleration, temperature and rotation. It unpacks them into seven numbers and prints the raw values. It also prints them converted to g (dividing by 16384) and degrees per second (dividing by 131).

Parts list

3 parts, plus the jumper wires. They retail for about $12.50; on Mokxi they're free.

Kits that can build it

This starter kit has every part in the circuit. Each kit's page lists what else it can build.

Wiring table

Every connection, pin by pin, read from the circuit itself. Each row joins the pin on the left to the pin on the right, by a jumper wire or a breadboard strip.

Part and pinConnects to
Accelerometer and gyroscope, MPU6050 pin SCLESP32-DevKitC V4 pin 14
Accelerometer and gyroscope, MPU6050 pin SDAESP32-DevKitC V4 pin 13
Accelerometer and gyroscope, MPU6050 pin VCC3.3 V
Accelerometer and gyroscope, MPU6050 pin GNDGround

The code

The MicroPython code exactly as the editor opens it. Change a line there and press Run: the board runs it on the official MicroPython firmware, with nothing to compile.

main.py · ESP32-DevKitC V4
# MPU6050: SCL on GPIO 14, SDA on GPIO 13, address 0x68. Wake it up,
# then read the accelerometer and gyroscope once a second, raw and in
# g and degrees per second (the default ranges: 2 g and 250 dps).
from machine import I2C, Pin
import struct
import time

i2c = I2C(0, scl=Pin(14), sda=Pin(13), freq=400000)
ADDR = 0x68
i2c.writeto_mem(ADDR, 0x6B, b"\x00")          # clear the sleep bit

while True:
    data = i2c.readfrom_mem(ADDR, 0x3B, 14)    # accel, temperature, gyro
    ax, ay, az, temp, gx, gy, gz = struct.unpack(">hhhhhhh", data)
    print("accel", ax, ay, az, "gyro", gx, gy, gz)
    print("g: %.2f %.2f %.2f  dps: %.1f %.1f %.1f" % (ax / 16384, ay / 16384, az / 16384, gx / 131, gy / 131, gz / 131))
    time.sleep(1)

Troubleshooting

The usual mistakes with this circuit, and the fix for each.

  • An error about the device not being found This project
    Check SCL on GPIO 14 and SDA on GPIO 13. Do not swap them. Also check power and ground.
  • All readings are zero This project
    The chip may still be asleep. The line that writes to register 0x6B wakes it, so keep it.
  • The sensor is not found or reads all zeros. Accelerometer and gyroscope
    Check SDA and SCL (A4 and A5 on an Uno), power, and ground. The I2C address is 0x68, or 0x69 if AD0 is high. The chip starts in sleep mode, so write 0 to the power register PWR_MGMT_1.
  • The values look wrong or the angles drift. Accelerometer and gyroscope
    Raw readings are counts, not g or degrees per second. Divide by the scale for your range (16384 per g at 2 g). Gyro angles drift, so blend with the accelerometer using a filter.
  • The board is not found, or upload fails with a connecting message. ESP32-DevKitC V4
    Use a USB cable that carries data, not charge only. Pick the ESP32 Dev Module board. If it still fails, hold BOOT while uploading starts, then release.
  • Some pins never read right, or the board will not boot with a wire attached. ESP32-DevKitC V4
    GPIO34 to 39 are input only and have no pull-ups. GPIO6 to 11 run the flash, so leave them alone. GPIO0, 2 and 12 are boot pins; avoid pulling them the wrong way at reset.

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