No pull up found on SDA or SCL - Issue

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gjk_baker
 
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No pull up found on SDA or SCL - Issue

Post by gjk_baker »

Hello,

There are hundreds of these posts in the forum. You have many years of products, learning guides, and changes. Maybe you could do an extensive and complete debugging application note on how to work out this issue in various implementations of hardware and circuit python. It would save us all a lot of grief and you a lot of questions and forum posts.

Using a ItsyBitsy nRF52840 Express (doesn't have resistors) with 1/2 Stemma cable soldered to the pins; connector to LIS3DH (Adafruit)
Getting the dreaded "No pull up found..."
Tried

i2c = board.I2C()
or
i2C = busio.I2C (board.SDA, board.SCL)

LIS3DH work because I am using it on another MCU (with resistors).
If I am probing with a DMM what should I be looking for.

As always, help is most appreciated

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mikeysklar
 
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Re: No pull up found on SDA or SCL - Issue

Post by mikeysklar »

The is often a wiring issue. Can you post photos of your connections and soldering between the ItsyBitsy nRF52 and your LIS3DH? Is the same stemma cable being used in your working scenario with the other controller?

Have you been running the provided example code:

https://learn.adafruit.com/adafruit-lis ... 2997974-26

Code: Select all

 # SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
# SPDX-License-Identifier: MIT

import time
import board
import busio
import adafruit_lis3dh

# Hardware I2C setup. Use the CircuitPlayground built-in accelerometer if available;
# otherwise check I2C pins.
if hasattr(board, "ACCELEROMETER_SCL"):
    i2c = busio.I2C(board.ACCELEROMETER_SCL, board.ACCELEROMETER_SDA)
    lis3dh = adafruit_lis3dh.LIS3DH_I2C(i2c, address=0x19)
else:
    i2c = board.I2C()  # uses board.SCL and board.SDA
    lis3dh = adafruit_lis3dh.LIS3DH_I2C(i2c)

# Hardware SPI setup:
# spi = board.SPI()
# cs = digitalio.DigitalInOut(board.D5)  # Set to correct CS pin!
# lis3dh = adafruit_lis3dh.LIS3DH_SPI(spi, cs)

# PyGamer or MatrixPortal I2C Setup:
# i2c = board.I2C()  # uses board.SCL and board.SDA
# lis3dh = adafruit_lis3dh.LIS3DH_I2C(i2c, address=0x19)


# Set range of accelerometer (can be RANGE_2_G, RANGE_4_G, RANGE_8_G or RANGE_16_G).
lis3dh.range = adafruit_lis3dh.RANGE_2_G

# Loop forever printing accelerometer values
while True:
    # Read accelerometer values (in m / s ^ 2).  Returns a 3-tuple of x, y,
    # z axis values.  Divide them by 9.806 to convert to Gs.
    x, y, z = [
        value / adafruit_lis3dh.STANDARD_GRAVITY for value in lis3dh.acceleration
    ]
    print("x = %0.3f G, y = %0.3f G, z = %0.3f G" % (x, y, z))
    # Small delay to keep things responsive but give time for interrupt processing.
    time.sleep(0.1)


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freddyboomboom
 
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Re: No pull up found on SDA or SCL - Issue

Post by freddyboomboom »

Note: The pullup resistors are typically on the Adafruit breakout boards. The controller (feather, qt py, etc) typically doesn't have pullup resistors.

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gjk_baker
 
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Re: No pull up found on SDA or SCL - Issue

Post by gjk_baker »

The part is good, because I checked with another MCU (with resistors) the LED lights and I get data out.
When attached to the ItsyBitsy nRF52840 Express the LED does not light.
On the Itsy 3V to GND 3.3V.
On the LIS Vin and 3Von to GND 0.6Volts? (3.3V on the other MCU)
Additionally, replaced the Stemma cable?
Untitled.png
Untitled.png (998.44 KiB) Viewed 94 times

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freddyboomboom
 
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Re: No pull up found on SDA or SCL - Issue

Post by freddyboomboom »

You have the orientation of the connector pinout reversed.

See https://learn.adafruit.com/assets/94423

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gjk_baker
 
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Re: No pull up found on SDA or SCL - Issue

Post by gjk_baker »

Thanks

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