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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Confused with grasping I2C clock and data bit transfer relationship

In I2C protocol one data bit is transferred during each clock pulse of the SCL. All the SCL-SDA timing diagrams I've encountered so far are shown as below: My problem is that instead of one bit of ...
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Identifying I2C to dual UART interface IC part number of DFRobot module

DFRobot has a nice I2C to dual UART adapter module DFR0627 and good Arduino library support. I am going to design a customized PCB with several hight speed UART based on Arduino + DFR0627 ...
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I2C read() lost 1 bit

I try to use I2C to read data from ADS1110, the address of ADS1110 is seven bits, which is 1001 000. Writing data can only change the configuration register, which ...
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What does I2C 'target address' mean? Can we not address individual registers in the target device?

The I2C specification says the addressed target device responds to the 7 or 10 bit target address. And the data transfer is always in 8 bits. Then, does it mean all the I2C target devices just provide ...
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Pull up and down resistors at the same time

I have an I2C circuit with a 4.7 kohm pull-up resistor for each line. I think it might be a too strong (too small in value) resistor and the data isn't read properly. The processor I'm using has the ...
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I2C Hot Swap design and feasibility

I would like to hear if someone has successfully implemented a working connectable/disconnectable I2C interface. I'm working with the back plane (host device) and am looking into implementing a I2C ...
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SPI MISO line not working

I am using a KSZ8463 Ethernet Switch IC. When I connect the SPI MISO lane to another board having 2 peripherals - CPU and a CAN Controller IC - there's a spike of 0.3A current and the Switch IC stops ...
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Is I2C write/read wearout possible for the MLX90393

I am using an MLX90393 on a custom-built and ordered PCB (there are no other components) in I2C-Mode. Please find the datasheet here. I am using the smbus library to read from the sensor around each ...
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How to convince lis2dh12 accelerometer to talk to me?

The device ACKs it's address and when asked about the WHO_AM_I 0x0f responds correctly with 0x33. However the "measurement ...
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Is this an I2C ACK? Else why are there 9 bits?

Since my previous question I've reduced the clock to 10kHz and am now trying to interpret what the pulses mean. My reading of the image is 0b00110010 being ...
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7 votes
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I2C short pulse during SCL==low

Somewhere around the end of transmitting a byte in Master Transmit mode the following is observed(SCL - yellow, SDA - blue). I am mainly interested in What is the tiny pulse on the right? STOP? ...
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I2C Strange goings on

I am using a Teensy 4.0 and an MCP23016 Port Expander (only I2C device) on my PCB. I have 4k7 pullups to 3V3 on SDA & SCK. SCK track is 77.9 mm long, 0.254 wide. SDA 64.3 mm long, 0.254 wide. I ...
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Detect how many push buttons are being pressed using a maximum of two Arduino pins

Imagine you have a varying number of push buttons that you need to connect to a microcontroller such as Arduino, of which you can only use a maximum of two pins (not counting 5v and gnd). Each button ...
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In I2C communication, let's assume 10 bytes are to be transferred from Master to slave. What happens if NACK is received after transfer of 5 bytes?

Is only erroneous byte sent again and communication resumes or communication is restarted? Similarly, what will happen if data is being received by master?
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STM32 I2C BNO055 has big spikes in data in fused mode

I am reading euler angles in fused mode from BNO055 device. It gets correct angles, but there are big spikes from time to time, but only when the values are changing. I am sending data over USB to my ...
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Why does I2C only run once in interrupt mode on STM32?

I've got a custom board with two stm32f4s (f411 and f446) that communicate via I2C. Now, I have two dummy programs, where f446 is configured as I2C slave and f411 is I2C master. If I just transmit ...
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I2C maximum value of pull-up resistor (explanation)

This is more of mathematical problem, but I think there is an electrotechnical engineer that can help me. So I was reading about I2C pull-up values in the Texas Instruments SLVA689 I2C Bus Pullup ...
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i2c oled display problem with STM32F401RE Nucleo Board

I have an i2c oled display with an SSD1306 driver. I want to drive this display with my nucleo card. Pin configurations are shown below. I provided the i2c connection on the display via i2c1 on the ...
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2 votes
1 answer
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MCP23017 open drain interrupts not working as expected

I have multiple MCP23017 ICs with their interrupts all connected in serial. The interrupt pins are configured to be open-drain. All the A port interrupt pins are connected together and all the B port ...
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STM32L073 I2C not sending 9th clock pulse

I have an STM32L073 communicating with an IS31FL3246 LED driver over I2C. Occasionally the MCU will not send the 9th clock pulse and therefore locks the bus. (As shown in the picture the analog ...
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STM32 - I²C Slave HAL Callback ACK

Objective: implement a single byte I²C slave on STM32. Materials: STM32L452RE Nucleo-64 board, HAL Library, CH341 USB-I²C adapter(1), Artix Linux with Runit, Rhode & Schwarz RTB2004 oscilloscope ...
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INA219- I2c bus weird behavior

I have a PCB assembly where I built the circuit in the schematic below. I did not start programming yet. I'm getting the weirdest problem. When I check the voltages in the SDA and SCL lines (which ...
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CH201 and CH101 pulling SDA line low after a while

I'm trying to get the TDK CH201 and CH101 sensors to work. After porting the API and writing the firmware to the sensor, I'm able to get range reading from the sensors. So I2C is setup and working, as ...
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Sensor power supply and GPIO pad voltage on different 1.8V rail

I'm using I2C to communicate between SOC and Sensors. My Sensor's power supply is 1.8V LDO output. And the I2C pullups are connected to same rail. But the pad voltage for my SOC GPIOs (where the I2C ...
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1 answer
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Topology and protocol for boards connection

Would like to have some insight on which data protocol to use to communicate between a master and several slave boards on a project i'm working on. My initial idea was to daisy chain all the slaves. ...
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Identifying EMI on I2C Bus

I am using an RPi to interface with a micro controller which, in turn, controls a motor. I am struggling with bus errors when the motor is enabled. The motor draws ~1A. All boards are connected to a ...
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2 answers
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ADS1115: Using 5V supply instead of 3V, do I need to increase the logic level signal from 3V to 5V?

I am using a microcontroller that has a 3.3V Logic level output. The microcontroller is connected to ADS1115 via I2C pins, and the ADS1115 can be powered with 3.3V or 5V depending on the range of ...
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2 answers
32 views

ATSAMD11C SERCOM I2C Pin Assignment

I am planning on using the ATSAMD11C14 (SOIC14 package) for a project that requires USB, 2 I2C busses, and some GPIO. The device has two SERCOMs, each has 4 pins assigned to it. When used in 2 wire ...
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1 vote
1 answer
37 views

Interfacing LCD via SPI

Problem: I am trying to figure out how to interface an LCD via SPI. What is known: It is 80x32 dot matrix. There are 23 pins on a flex cable. The pinout. I'll put it below. The LCD is marked with red ...
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1 answer
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Sensor - Use level shifter or not?

I try to design an electronics with a VL53L1CXV0FY/1 ToF sensor. The uC has a logic level of 3.3V and the ToF sensor seems to have different logic levels, but I'm not sure what I should choose. ...
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Running a thermal camera (AMG8833) with an orange/raspberry pi but i2cdetect cannot detect any of the 2 cameras

I have bought 2 AMG8833 thermal cameras from different sellers. I tested both first with an orange pi zero and later with a raspberry pi zero. On the orange pi, I used the following GPIO pins and ...
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4 votes
3 answers
534 views

Can someone help me understand this code for the ADXL345 accelerometer?

I'm trying to learn how to read the angles measured from an ADXL345 accelerometer (Adafruit) for a beginner project where the sensor will be attached to a short stick and I want to read the angles I'm ...
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1 answer
58 views

Maximum input voltage Black Pill

I have a sensor outputting a 0.8 - 5.0V signal, where this analog signal is read by a 16-bit ADC, the ADS115. The ADC is capable of reading the maximum 5V signal since I am powering the ADS with VIN = ...
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3 answers
775 views

In I2C communication, slave not able to pull down properly during 9th clock pulse (not giving proper ack)

I am trying to communicate from master to slave using I2C communication. But during the 9th clock cycle, the slave is trying to pull high to low but it can only pull it down to half the voltage (3.3 V ...
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1 answer
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Three or four-wire plugs for electronic lab use

I'm doing experiments with various sensors and I'd like to build peripherals with three or four pin plugs. This is DC power (3 or maybe 5 volts) and either an analog signal or low-speed I2C. I'd like ...
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0 answers
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Mux Auto Addressing Circuit

I am trying to build a circuit that will allow multiple (up to 4) muxes on the same I2C line. I am trying to get their addresses to increment with each new board connected. (Lines A0 to A2). Here is ...
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1 vote
2 answers
93 views

Reading angular velocity from multiple rotary encoders

I am working on a project, where I need to get reliable data from 4 incremental rotary encoders. The motors can spin at a maximum of 100 RPM, with 420 pulses per revolution. This makes a single ...
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1 answer
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Intel FPGA Avalon I2C (Master) Core IP: Where are SCL_OUT and SDA_OUT?

This is for Intel MAX10 (10M08) FPGA, NIOS 2 soft core, Quartus (free version), windows 10. I'm trying to understand this ip core because I need to connect external tri-state buffer to it. The thing ...
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1 vote
3 answers
188 views

I2C high speed mode

I am working on a project which requires communication from a central controller and multiple peripheral sensors. Each sensor can push out data at a rate of 4-5KB/s(kilobytes/sec). There are 25-30 of ...
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3 votes
1 answer
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Extract a 6 pin connector pinout with serial protocol

I have an intercom display, Elvox 5721, and I'd like to program it with its software, called "saveprog". It has a 6 pin programming connector which requires Elvox's cable which is called ...
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2 votes
3 answers
349 views

I2C Slave pulling SCL LOW and not returning data

I'm trying to interface the OMRON D6F-PH0025AD2, BME280, and a 2004 Display (with an I2C driver) with an ESP32. Without the D6F on the I2C lines, the others peripherals work perfectly. Following the ...
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3 votes
1 answer
311 views

I2C Connection with ADS1115 not working

I have trouble by setting up an I2C connection between ESP32 NodeMCU and ADS1115 (datasheet). Wiring: I'm using the below example code from Adafruit: ...
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1 vote
0 answers
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SFP proper address to read length

According to SFF-8472, there are 6 addresses (14 to 19) in table A0 for link length. And when I read a couple of SFP modules trough I2C, I see that more than one of these addresses contain value other ...
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2 answers
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Is it possible to send data through I2C with TIM without CPU interrupt and just DMA Interrupt

Because I've seen HAL_TIM_Base_DMA_START() in the STM32F7 HAL timer library, I though maybe it is possible to, for example, call HAL_TIM_Base_DMA_START() and timer continually requesting DMA to ...
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Intel FPGA MAX10: How do you connect the buffers to the I2C IP core?

This is for Quartus Lite 21.1 (free version), MAX10 (10M08) and NIOS II, BeMicro MAX10 development kit. I know very little Verilog and no VHDL. I'm trying to learn more about FPGAs so I dusted off (...
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2 answers
116 views

VGA DDC voltage

While designing a pcb with a VGA output, I came across the DDC pins on the connector. I'd like to use that protocol to retrieve data from the monitor. After searching on the internet, I found that the ...
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-1 votes
1 answer
104 views

How to connect BME280 to ATmega328?

I tried to connect a BME280 sensor to an Arduino Uno. After a successful experiment, I decided that I needed to transfer the sensor and the microcontroller to a separate board without unnecessary ...
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1 vote
0 answers
71 views

ATtiny85 sharing SPI and I2C pins

I have an ATtiny85 sending messages via LoRa over SPI and I've hooked up a BME280 on I2C which I'm using with the TinyBME280 library. Everything is fine until I read the temperature, which then hangs ...
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1 answer
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SSD1327 OLED-driver C-library

Since a pre-made I2C C-lib for the SSD1327 does not exist anywhere, I'm trying to create one by hand for the STM32 HAL without ...
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2 votes
2 answers
473 views

Can I use two I2C interfaces on the same STM32 MCU to communicate between each other?

I have an STM32 Discovery board and I want to test the I2C protocol but I don't have any other devices to test with. I want to know if I can use two I2C interfaces on the same board just to act like ...
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