I2C gives me the Error "OSError: [Errno 5] EIO" with GY-521 (MPU6050)

[Moebelix]

Hello everybody,

I am new to this forum, so please excuse if I am writing in the wrong area.

I have been fighting to get a GY-521 accelerometer and gyroscope board running on a RP2040 Type C 16mb Chinese Clone, and also on a different clone.

I am able to initialize a I2C object
I am able to use the scan function and it finds the address of the MPU6050 (on the GY-521 board)
But I am not able to read anything from the MPU6050

from machine import Pin, PWM, I2C
from time import sleep
import utime
from imu import MPU6050
from deltat import DeltaT
import fusion

i2c = I2C(0, sda=Pin(20), scl=Pin(21), freq=400000)


devices = i2c.scan()

device_count = len(devices)

if device_count == 0:
    print('No i2c device found.')
else:
    print(device_count, 'devices found.')

for device in devices:
    print('Decimal address:', device, ", Hex address: ", hex(device), "\t\t")
        
sleep(1)

#print(i2c.readfrom(0x68, 6))

#print(i2c.readfrom_mem(0x68, 0x3B, 6))

testbuff = bytearray(6)    
i2c.readfrom_mem_into(0x68, 0x3B, testbuff,addrsize=8)

I get the following output:

>>> %Run -c $EDITOR_CONTENT
1 devices found.
Decimal address: 104 , Hex address:  0x68 		
Traceback (most recent call last):
  File "<stdin>", line 30, in <module>
OSError: [Errno 5] EIO
>>> 

I have tested an other GY-521 board and a PCA9685 board with the same results.

I have tested all of these boards with an arduino uno, and they worked fine (both with 3.3V and 5V)

Does anybody know what I am doing wrong?

[karfas]

Just search the forum for i2c "errno 5".
Most likely, your wiring misses pull-up resistors or you are using the wrong pins for i2c.

[Moebelix]

I am sorry, I just tried the pull ups again and it worked.
Thank you for the quick help

[robert-hh]

The soft-PullUp resistors are usually too weak (like 30kOhm). They may be good enough for a scan(), but fail at longer data. Better attach external ones in the range of 2.2K - 10k Ohm.

[Fidoooo]

Hi, could you please share the final code you used? I am having similar issue and I am getting a bit clueless here

[baldingwizard]

I had this exact problem for an AHT21 sensor. Added external 10K pull-ups and communication worked like a charm. Thanks @robert-hh - really appreciate the tip.

EDIT: Actually, I've just tried without the pullups and it's still working.... hmmmm. Perhaps it depends on noise and frequency. I only have the single device on the bus. Trying without the pullups but with reduced i2c frequency as I'd rather get away without pullups if I can (to simplify the build onto a Pico).

[baldingwizard]

I've just re-tested this without external pullups and a drastically reduced clock frequency on a Pi Pico, with the AHT21 connected directly to pins 1 (SDA), 2 (SCL), 3 (GND) and 4 (Vin) with the internal pullups enabled. The plan is to directly solder the 4-pin module to the Pico without any other external components. Note that as it's low power I'm actually powering the module using GP2 - since it's a very low-power module and well within the limits - so I can switch the module on by setting GP2 high and then read the sensor values using i2c0 on GP0 and GP1, switching it off again if I need to save power. It seems to work reliably so far (I only need a low frequency so tested with freq=4000).