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Questions tagged [i2c]

I²C (Inter-Integrated Circuit) is a multi-drop serial bus invented by Philips (now NXP) for communication between ICs on the same PCB, i.e. short distance.

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Disconnecting I2C from powered battery gauge IC to rest of the unpowered circuit

The LTC2944 is leaking current into my unpowered side of the circuit, cutting the traces between this IC and the rest of the circuit fixed it. Can I do the following to prevent this leakage? When the ...
Tomás Arturo Herrera Castro's user avatar
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Servo moving to limits randomly

I've seen a very similar question to this but want some extra pair of eyes on my circuit here. The issue I've encountered is on startup of this script every so often the servos will randomly move to ...
msalaz03's user avatar
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Help identifying I2C sensor from Propel Star Wars Drone

I have a sensor from a Propel Star Wars drone that I can't identify. The metal part of the sensor is marked with "A6103 040". I have tried various libraries and sensors, including BME280, ...
Halit Efk's user avatar
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Can I put schottky diodes in I2C line to prevent LTC2944 from powering my circuit through SDA and SCL?

I am using a LTC2944 connected to a battery that fluctuates between 11V and 14.4V. SDA and SCL lines go to a microcontroller and other peripherals (also connected to 3V3 via 10k resistors). I can read ...
Tomás Arturo Herrera Castro's user avatar
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I2C Write Function and Making the Array User Inputtable with Python

I'm wrapping up the firmware for my project using 4 TCA9548As to switch between 32 different ports for I2C slave devices. I have a raspberry pi and clamp on master SDA and SCL lines for master input. ...
Beau Raley's user avatar
2 votes
2 answers
56 views

Can MUXs or their channels be sperate busses?

I am doing a little project with some MUXs. PCB is currently being built; I'm waiting for it to be shipped out to me. I have multiple MUXs on my board (TCA9548As). They are connected to a master pair ...
Beau Raley's user avatar
2 votes
2 answers
155 views

A question about I2C resistor locations and bus capacitance

When an MCU is communicating with a sensor or DAC: does it matter where the pull up resistors closer to? and when calculating the bus capacitance, should always both the sensor and MCU input ...
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I2C: SDA and SCL Lines Pausing Between GND and VDD

I'm seeing communications on an I2C bus are momentarily pausing between GND and VDD (3.3V) during some transactions. See scope shot of the SDA line below: Since it stops at about 800mV, this is below ...
oneil's user avatar
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TCA9548A I2C Python coding help

I am designing a board using 4 TCA9548As that each have 8 screw terminals so that I can connect to 32 addressable devices. I am trying to create the python code to be able to write to each of these ...
Beau Raley's user avatar
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What determines I2C interrupt service time after address byte ACK?

I am looking at the NXP spec for I2C and what I don't understand is the timing constraint for the portion of the transmission where the "clock line held LOW while interrupts are serviced" (...
tronhawk's user avatar
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Using MUXs to Address Multiple Devices

I am fairly new to I2C and coding in general as I am currently majoring in electrical engineering. I needed to design a board with multiple MUXs, I am using TCA9548As, that can address interchangeable ...
Beau Raley's user avatar
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I2C register reading with long wait time

I'm developing a vibration and temperature analysis system. To do this, I have developed a sensor based on an STM32L053C8 chip and a KX122-1037 accelerometer. Looking at the datasheet, this ...
Matheus Markies's user avatar
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1 answer
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Reading multiple push-button switches on a raspberry pi using an mcp23017 over C++

Having followed various tutorials on the web (i.e. 1,2), I have made the following connections: To enhance clarity, I post another picture depicting the connections on the mpc23017 using a cropped ...
cestpasmoi's user avatar
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Does this board already have pull up resistors for I2C? [closed]

I want to use this type of Nucleo board to communicate with a device which requires both SPI and I2C protocols. I know that SPI is directly connected but I2C requires pullup resistors. Does it mean ...
user1245's user avatar
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DC isolation - 3 separate circuits with same power source and shared I2C

I am trying to build one small project and based on the needs I need to isolate few components but also keep them connected using I2C. I was doing a research and found few DC DC isolator converters ...
Peter Bašista's user avatar
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Which ATtiny TWI parameter provides more robust operation?

I'm using an ATtiny3226 as an I2C client (slave) interface in a robot, to get commands from the main controller (single master) using I2C on a shielded cable. There are brushless and servo motors ...
Tirdad Sadri Nejad's user avatar
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Weird I2C Problems

So, currently we are having problems with the I2C Communications on our cabinet Each row on the cabinet has 5 boards which have 2 16bit io expanders each board has 32 devices and there are 4 boards in ...
reppp's user avatar
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What will happen if I2C pull up voltage became zero

This is a continuation of this question. In my board RTC I2C lines are pulled up to controller supply voltage and the controller supply voltage will be off when the system is off. At that time also ...
Confused's user avatar
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LIS2DW12TR accerometer overheating massively when connected with I2C

I have 4 LIS2DW12TR accelerometers connected to an Seeed Studio ESP-32 S3. The accelerometers get extremely hot when they're connected to 3.3V. They are not recognised with an I2C scan. The ...
okay_computer's user avatar
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STM32 I2C bus stuck

I'm trying to setup a mini OLED display I2C (SSD1306) with the STM32F411 (black pill). Sometimes it works, randomly. But always, after power off/on everything, it stops working and doesn't recover. If ...
Gos's user avatar
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can tm1637 be used with the built-in i2c of any device

I am using a tm1637 IC not the module to display 4 digit seven segment display, well I am able to make it work, but it uses any 2 digital pins as clk and dio, but I want to make it work with the i2c ...
Dhanush's user avatar
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How do I increase I2C/Wire Timeout on Teensy41

I am working on an I2C system with a Teensy41 master and an Adruino NANO as a slave. It currently takes the NANO about 700 microseconds to do a calculation and reply to the request for data from ...
Hubert B's user avatar
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I2C Level Shifting (Adafruit breakouts)

I have programmed an I2C slave on an Arduino Nano and an I2C master was on an Arduino Mega. I'm now working on upgrading the master to a Teensy 4.1. The new master is a 3.3v microcontroller, where as ...
Hubert B's user avatar
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PCA9615DPZ burns out continuously

I need help with a problem I'm having with the PCA9615DPZ chip, a differential I2C buffer. I have two boards, both of which have this circuit: The boards communicate with each other without problems. ...
Federico Massimi's user avatar
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What is the memory address for 24AA16 EEPROM IC?

I am using 24AA16 EEPROM IC to read and write. But i don't know exactly the memory adddress to write something in this IC and also read from that. This is the datasheet for this IC, https://ww1....
Kuralmozhi's user avatar
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I2C on SAMD21 with Atmel Start works only in one direction

I am trying to establish a half-duplex I2C communication between two ATSAMD21G18A microcontrollers, using Atmel Start's I2C functionality. (HAL Synchronised I2C) The automatically generated example ...
aulven's user avatar
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2 answers
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I2C LOW-level output voltage

I've been confused about electrical characteristics table in I2C specification (Table 10) What are differences between LOW-level input voltage and ...
Emre's user avatar
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1 answer
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I2C slave not ACKing with one MCU but ACKing to arduino Nano

I am trying to communicate with a cypress MCU (at 100kHz) that has been configured as I2C slave with adress 0x48. the document says the following. Now when I send this adress from my Sinowealth MCU, ...
Saqib Sohail's user avatar
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Tie to VDDIO for I²C Interface

I want to communicate to a sensor that supports I2C and SPI. I want to use I2C and the datasheet says "Tie CS to VDDIO for I²C Interface", do I need to connect a resistor to limit the ...
PeterM's user avatar
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TCA9548A I2C PCB Design issue

I am designing a PCB that connects to a 40pin header (similar to RPi HAT header) on an AAEON embedded computer. The computer has a SIO chip and an API that allows I2C communication from the device. ...
Denis's user avatar
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1 answer
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OLED Libraries interfere with PD6 port manipulation in Atmega328PB

I stumble across an issue which I can't solve in multiple attempts. I'm trying to turn on and turn off an OLED SSD1306 display attached to the hardware I2C on Atmega328PB. The device has button on PD3 ...
lz_linux's user avatar
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I2C_SCL_SDA_Low level voltage issue

We have issue with I2C rise time during 1MHz of data transmission on the device side. We have tuned Rp2 pull value to 1k and 2.2K still the issue remain same. If reduce the pullup value the rise time ...
chitharanjan M's user avatar
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1 answer
175 views

Which pins are used for I2C and SPI in ESP32-S3?

I am using ESP32-S3-WROOM-1-N16R2 Controller in my design. I want to connect Sensor with this module which has both I2C and SPI Communication pins. I gone through the datasheet for controller, but i ...
Kuralmozhi's user avatar
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88 views

ATmega328 experiences freezing or hangs when the ceiling fan is turned on or off

I've been working on a project, but I've hit a snag. Every time I try to turn the ceiling fan on or off, ATmega328 gets hung/freezes. Let me break down the project for you, so you know what's going on ...
mechaTronics Tech's user avatar
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FT232H USB to I2C Device Not Detected

I am using an IC from FTDI, FT232H. I am using it to connect to a video decoder, via I2C, from a USB port on my type6 CPU module. I am able to detect the FT232H and install the proper driver on the IC ...
miggyEE's user avatar
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1 vote
1 answer
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STM32 I2C HAL Code GPIO?

I configured PB6 and PB7 to I2C using the CubeIDE GUI, and it automatically generated the code for me. I understand how I2C works but I am trying to see how HAL does it and this is the code that they ...
jdsus's user avatar
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SCL line Pulled Low all the time

I have made a custom PCB with nRF52840 and Three slave Devices(IAM-20380 Gyro), (ADXL372 Accelerometer), (VCNL4040 Proximity ) Sensors. All slaves are connected to one I2C Bus When I plug only power ...
Zunuran Nasrullah's user avatar
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SLF3S-4000B not recognised by Arduino Uno R3

I have a Sensirion SLF3S-4000B connected to SDA/SCL lines of the Arduino uno through a logic level shifter (connected like in this example: https://learn.sparkfun.com/tutorials/retired---using-the-...
CadeO01's user avatar
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2 answers
67 views

Using 7pin OLED 128x64 with iic

I just bought the 0.96” Monochrome OLED Display (SSD1306) and it claims to support both SPI and IIC/I2C with 7 pins. I want to use it with an Arduino Uno R3. How do I go about doing this and ensure ...
Aditya Jain's user avatar
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42 views

Communication Issue with TCA9539 on MSP430FR4132

I am trying to communicate with the TCA9539 using my MSP430FR4132, but I'm encountering issues setting the registers using I2C. I've connected pull-up resistors (10kΩ) to both the SCL and SDA lines. ...
Aswin Raj K's user avatar
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2 answers
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I2C: How much may SCL frequencies of several masters in a multi master bus differ?

And what will / may happen if the two master SCL frequencies are very different = so much that even when starting at the same SCL falling edge they will be opposite in phase before 9 SCL pulses are ...
Martin_from_K's user avatar
1 vote
0 answers
42 views

I2C1 busy flag always high STM32F103RB

I finished my I2C peripheral drivers and I would like to test it with my BH1750 sensor but I am having an issue. When I initialize the I2C1 peripheral, everything is smooth but then I notice that the ...
jdsus's user avatar
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7 votes
2 answers
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Why do the I2C pullup resistors in the datasheet differ so much from my calculations?

I´m using the LSM6DSR accelerometer/gyroscope from ST on a project. Looking into the application hints, it suggests using a 10k resistor as pullup for SDA AND SCL: Since I´m using another slave (...
DMinatto's user avatar
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1 vote
1 answer
195 views

INA228: My I2C code works on the dev board but doesn't on my custom board

Part number: INA228 from Texas Instruments MCU: msp430fr2433 I initially brought a current sensor from Adafruit that used an INA228 chip. After some challenges, I managed to get the I2C communication ...
varun's user avatar
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1 answer
182 views

SSD1306 128x32 OLED change I2C address

Hey all I've been looking for any information that would allow me to change the I2C address for the 0.91" OLED 128x32 module: So far I have only found mention of the I2c address change here but ...
StealthRT's user avatar
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Multiplexing signal array

I have a specific application where I need to interface 256 i2c busses arranged in array of 16x16. I have used multiplexers to create LED arrays, but this problem seems different as there isn't part ...
somerandomusername's user avatar
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1 answer
84 views

Data sheet says 14 bit output, I am getting 16 [closed]

I am doing a project on Cube IDE using a Nucleo board and a magnetometer. In the data sheet for the magnetometer I can either have a 12 bit output or 14 bit output. I have set it up so I get 14 bits ...
Elliot Walster's user avatar
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1 answer
73 views

Why are GPIO Expander Registers Being Rewritten?

I'm using an LPC1768 microcontroller (mbed) and 4 GPIO expanders (MCP23017). I am trying to write to the expanders to enable the pull up resistors and some other functions, but am getting strange ...
Nate.Olson's user avatar
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4 answers
102 views

Extending EEPROM I2C addressing

So I have a interesting problem that someone could give their input. I'm working on a project where I have 100 "devices" each with its own EEPROM. The "devices" can be connected ...
somerandomusername's user avatar
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1 answer
54 views

connecting sensirion SLF3S-4000B flow sensors to arduino uno r3 via I2C bus

I bought the following sensors for my project: https://www.farnell.com/datasheets/3730435.pdf I am using two and they operate on 3.3V logic. They use a standard 6 pin picoblade 150mm connection. I am ...
CadeO01's user avatar

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