Not detected pull-ups in an official card

[NicolasCheinet]

CircuitPython version and board name

Adafruit CircuitPython 9.2.8 on 2025-05-28; Seeed XIAO nRF52840 Sense with nRF52840

Code/REPL

import time
import board
import digitalio
from adafruit_lsm6ds.lsm6ds3 import LSM6DS3

led = digitalio.DigitalInOut(board.LED)
led.direction = digitalio.Direction.OUTPUT

i2c = board.I2C()
#board.SDA, board.SCL
while not i2c.trylock():
    pass

print("I2C ready")
i2c.unlock()

#sensor = LSM6DS3(i2c)

while True:
    #accel_x, accel_y, accel_z = sensor.acceleration
    #print(f"Acceleration: X:{accel_x:.2f}, Y: {accel_y:.2f}, Z: {accel_z:.2f}")
    led.value = not led.value
    print("Hello World !\n")
    time.sleep(0.5)

Behavior

This code, running on the code.py of CircuitPython 9.2.8, is not working because an only weird thing :

RuntimeError: sda or scl needs a pull up; check ](runtimeerror: no pull up found on sda or scl; check your wiring)

But it's on a card with the pull-ups on it, they are on the schematics and on the PCB. I tried with busio and with lines to let I²C find them.

I also have all the good file tree for the adafruit_lsm6ds lib.

Thanks in advance <3

Description

No response

Additional information

No response

[dhalbert]

On the schematic the LSM6DS3 is connected to INTERNAL_I2C_SDA and INTERNAL_I2C_SCL, which are different pins than the external SCL/SDA pins.

Those pins are named board.IMU_SCL and board.IMU_SDA.

from pins.c for the board:

    { MP_ROM_QSTR(MP_QSTR_IMU_SCL), MP_ROM_PTR(&pin_P0_27) },
    { MP_ROM_QSTR(MP_QSTR_IMU_SDA), MP_ROM_PTR(&pin_P0_07) },

[NicolasCheinet]

Thanks for the reply, but I just tested it and its the same issue happening all time... even with busio and board.IMU_SDA and board.IMU_SCL.

But really thanks and how can I know for the future how to find real name of pins ?

Sorry the issue is in french but it's saying that at line 10 : runtimeerror: no pull up found on sda or scl; check your wiring.

[bablokb]

Hm, I think busio needs scl as first and sda as second argument.

[NicolasCheinet]

It doesn't working either...

[Neradoc]

There's a power pin to enable too.
Try this code, it works on mine.

import board
import busio
import time

# sensor
from adafruit_lsm6ds.lsm6ds3trc import LSM6DS3TRC as LSM6DS
from digitalio import DigitalInOut
imu_pwr = DigitalInOut(board.IMU_PWR)
imu_pwr.switch_to_output(True)
time.sleep(0.1)
i2c = busio.I2C(board.IMU_SCL, board.IMU_SDA)  # IMU SCL/SDA
sensor = LSM6DS(i2c, address=0x6A)

while True:
    acceleration = "Acceleration: X:%.2f, Y: %.2f, Z: %.2f m/s^2" % (sensor.acceleration)
    gyro = "Gyro X:%.2f, Y: %.2f, Z: %.2f radians/s" % (sensor.gyro)

    print("acceleration, gyro")
    print(acceleration)
    print(gyro)

    time.sleep(0.1)

acceleration, gyro
Acceleration: X:1.03, Y: -6.61, Z: -6.96 m/s^2
Gyro X:0.02, Y: -0.07, Z: -0.00 radians/s

[NicolasCheinet]

Ohhhh you're right I just see it now we have to enable a pin to start I²C. THANKS all fast and kind amasing community <3.

My final code is up here