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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55 views

SFP, accessing EEPROM?

I have a SFP compatible module which has an I2C interface. I understand that SFP is a pseudo-standard but I can't find any documentation on the I2C interface and what registers in the EEPROM do what. ...
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95 views

I2C bus pollutes power rail

Working on a new revision of a design with a new I2C LED driver connected to SAM S70 Cortex-M7, I noticed some high speed ripple on 5V rail when using a 1Ghz scope. The PCB has 2 I2C buses and both ...
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Can an LTC4311 I2C amplifier be used along with PCA9515A I2C repeater

Can the LTC4311 (click for datasheet) be used along with the PCA9515A (click for datasheet) I2C bus repeater? EDIT to describe my goal: I am using a RaspberryPi4 with around 1m long cables and the ...
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Why won't DS3231 Real Time Clock continue ticking when powered only from VBAT?

I've got a custom STM32 board that uses a DS3231 RTC for date/time stuff. When the board is fully powered I can communicate with the DS3231 over i2c and write and read the time/date. Once the power is ...
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48 views

I2C seems to work but all register reads return 0s

I'm debugging an audio codec WM8962B via I2C. I wrote basic code for a manual I2C read operation of a given register. I'm using PSoC 5LP to do it. The 7bit slave address is 0x1A and I'm trying to read ...
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44 views

I2C via MCU works with FLAG_WRITE_READ but not FLAG_READ

I'm reading the date from an RTC via I2C using a SiLabs MCU. There are two different flag options, but only the 2nd one works. I'm new to implementing I2C, what is happening on the wire that works ...
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32 views

Use USB-C breakout board to connect TOF-sensor to an Arduino

I need some help with connecting my VL53L0X - TOF sensor to my Arduino Nano Every. I already connected it and am reading three sensors successfully over the I2C bus. I now want every sensor to be ...
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1answer
59 views

HAL_I2C_Master_Transmit_DMA sends only one byte

i am having an issue using STM32G4 with I2C DMS and FreeRTOS. I have used the library https://github.com/firebull/STM32-LCD-HD44780-I2C for a long time with STM32F4 and free RTOS and it works ...
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Can I and how I use datasheet registers to activate scaling up on the RTD2660 display controller?

I have a chinese display with hdmi driver board using RTD2660 controller chip. I want to use it to mod my Playstation portable with a bigger screen, but the problem is that psp outputs image with ...
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DFRobot_RGB1602 library does not work properly with DFRobot DFR0554 and Raspberry Pi Pico

Problem summary: set_cursor(0,0) brings text to (2,1) and set_cursor(0,1) brings text to (3,1), texts goes to imaginary 3rd line before 2nd line as if a 20x4 display. I modified the Python code to ...
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Proteus I2C slave and SPI slave primitive

There is a modeling primitives category in Proteus VSM, which contains I2C slave and SPI slave primitives from the DSIMMDLS library. Device notes for each say the following: "This primitive can ...
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50 views

Power Consumption for Open Drain Communication

When using an open drain communication scheme, like I2C, it seems that the majority of power consumption comes from the sinking of current through the pull up resistor when a logic 0 is transmitted. ...
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3answers
68 views

ESP32 I2C Circuit

I am using I2C communication with the ESP32 as the master. Do I need pull-up/pull-down resistors on the SDA and SCL lines? I could not find anything on the datasheet that said whether there were ...
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73 views

STM32f7 I2C master transmission using DMA does not work

The problem is the code: HAL_I2C_Master_Transmit_DMA (&hi2c1, (uint16_t)(MCP4725A0_ADDR_A00<<1), (uint8_t *)buffer, 2); Though it returns ...
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1answer
34 views

Does the MCP4725 support clock stretching? Does DMA need clock stretching in STM32F7?

I'm trying to send data to an MCP4725 through DMA in STM32f746ng but I can't. I'm thinking maybe DMA requires clock stretching and the MCP4725 does not support it? (I couldn't find anything about ...
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82 views

I2C slave pulls down SCL while doing nothing

I have an MCU (Texas Instruments tm4c123gh6pm) in which I have configured an I2C slave device. I have taken 3.3V from the MCU pin that provides them and connect them to two 4.7 kOhm resistors (to make ...
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1answer
51 views

I2C SCL goes low if using MCU GPIOs as pull-ups

I have an MCU (tm4c123gh6pm) in which I have configured an I2C slave device. At the moment I don't have resistors to wire the required pull-ups, so I want to use two of the MCU's GPIOs for this ...
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67 views

Read MPU6050 over I2C with STM32 nucleo board

I am working with a NUCLEO-F401RE board and I want to connect the accelerometer sensor MPU6050 (on a GY-521 module). The device can be connected to the board over I2C. I connected the 3.3V of the ...
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1answer
68 views

Best practices for low power consumption (battery operated) I2C pullups

I'm working on a battery powered device and am trying to extend battery life by using a lot of interrupt and timer driven code on the microcontroller (keeping it sleeping most of the time) and putting ...
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1answer
55 views

Level shifter for interfacing SCD41 and Raspberry pi over I2C

I am connecting an SCD41 CO2 sensor to a Raspberry Pi Zero 2 W. To keep the 3.3V current draw low, I would like to power it at 5V (peak current is 205 mA at 3.3V vs. 137 mA at 5V). A TXS0108E module ...
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4answers
114 views

In which clock edge does the I2C slave write?

I'm trying to implement an I2C master - slave example in an FPGA (Verilog). As the I2C protocol specifies, the master must make sure that it writes the next bit enough time before the clock signal ...
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1answer
121 views

I2C versus interference

I'm going to drive a bunch of 230VAC motorized ball valves from an ESP32. I'll have several boards, each with 8 triacs driven by MOC3052 opto-triacs. This will be connected to another board with an ...
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35 views

MCP23016(I2C pin expander) not detected when pullups are present

I am using an ESP32 which has multiple devices connected to it via I2C(4 Attinies, MPU6050 and MCP23016(pin expander)). I2C scanner wasn't detecting it when pullup resistors(4.7k) were anywhere on the ...
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29 views

I2C Communication for Mbed Program between Two NUCLEO-WB55RG Boards Fail

Really hope if there is someone have a quick look and give out a solution as soon as possible as the project is going to due very soon. Through the following code, I can allow sender board sending ...
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2answers
103 views

Modelling I2C capacitance for cables under water

My setup works fine with following combination of hardware: Raspberry Pi4 connected to a TCA9548A I2C Multiplexer from Texas Instruments, whereas each channel is connected over 4wires (GND, VCC, SDA, ...
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76 views

I2C Port on Raspberry Pi RPI4 recognizing arbitrary sensors

I am using a TCA9548A I2C Multiplexer from Texas along with two I2C sensors 'behind' / in series with each of the 8 Multiplexer channels. The Mulitplexer has the address 0x70, the two sensors have ...
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458 views

Pull-up resistors on I2C port

Hi everyone, I am confuse about I2C pull-up resistors. I use 4 I2C sensors. I am not sure is it true that pull-up resistors count. I use every sensors for pull-up resistors. If I use just one I2C port ...
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1answer
33 views

Unable to read anything but version information from MMA9555L

I'm currently working on a project that uses a MMA9555L from NXP. I'm trying to acces the chip via I2C but the only thing I can access is the version information. This gives me the impression that the ...
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92 views

When buying parts with serial interfaces is it useful to check timing requirements?

When buying parts with serial interfaces is it useful to check timing requirements? I'm especially curious about something like I2C; is it generally enough to see that a component is capable of ...
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About the I2C interface circuit of the Raspberry Pi Camera V2.1

Today, I get the schematic of the Raspberry Pi Camera V2.1. A snippet: The I2C interface on J1 is routed to the camera through Q1. You see, both the gate and the source are pulled up to 1V8. For SCL, ...
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102 views

Voltage issue on pull-up resistor

I have an I2C sensor circuit, 3.3V applied to SDA and SCL pin through 10k resistor. I2C communication is not working so I have measured the voltage drop across the 10k resistors. It drops 2.86V and ...
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120 views

Weird readings with INA219 Current/volt sensor, Arduino and big, fat scary Lipo

I have a strange situation with an I2C INA219 current/volt meter module (datasheet). In front of me, I have a rather scary 16.8V lipo - its positive output is on the VIN+ of the INA219. The VIN- leads ...
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ATSAMD21 (arduino) is pulling ports low when calling wire.onRequest()

The intent: Using the controller and I2C for turning a port high and low and querying for data from an agent. The setup: Two Adafruit Itsybitsy M0 Express (ATSAMD21) connected via I2C, 4k7 pullups on ...
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77 views

I2C communication pin and/or device getting damaged

I have a Raspberry Pi communicating with some I2C client devices. Occasionally either the I2C client device fails or a Raspberry Pi pin (one of the I2C pins) is damaged. The only thing I can conceive ...
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77 views

How can I figure out the i2c address of an OLED display?

I've got an OLED display I am trying to write to from my Raspberry Pico. It's an SH1106 driver. I can write fine when I set the i2c address to 0x3C, but behind the display there are two i2c address ...
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49 views

Level shifting I2C with VREF1 = 2.8V and VREF2 = 3.3V

I'm trying to connect a few devices on an I2C bus - primarily a GNSS module and a microcontroller. The microcontroller is the bus controller and must run on 3.3V, while the GNSS module internally uses ...
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1answer
49 views

Data frame ACK bit is always high from I2C target device read

I am using a Raspberry Pi Zero board as an I2C controller and a Raspberry Pi Pico as an I2C target and passing data between them using I2C. I use something like this: ...
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Why is this LSM303d register address being used with an OR and an address operator?

I'm trying to get the data of a LSM303d accelerometer using anSTM32 via the I2C bus. I've found online that to get the data from the OUT_X_L_A register (low byte of x component of the accelerometer) ...
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1answer
68 views

How is I2C signal integrity maintained over monitor cables for EDID?

Computer monitors (and other similar display equipment) use the I2C protocol with 5V signal levels to send EDID information to the "host". I2C's typical use case is for short connections on ...
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1answer
80 views

Noise on I²C when bit-banging but not with built-in I²C (ATmega328PB)

I'm working on bit-banged I²C for the ATmega328PB. I've been seeing a lot of noise (ringing and cross-talk) on the lines but thought it was just my test probes, etc. However, when using the MCU's ...
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1answer
41 views

set defined output state at start

I'm controlling a trigger system through fiber links. The optical transceiver for triggering the pulse that activate the channel is commanded by a port expander IC to which I send commands through I2C ...
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88 views

Problem with Interfacing of Multiple I2C Sensors

Problem Description I'm working on a project involving multiple Proximity sensors (AdaFruit VCNL4040). There are 8 such sensors interfaced through a I2C multiplexer (NXP PCA9547). Additionally I need ...
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100 views

Figuring out communication protocol

Complete beginner trying to learn by doing here... Background: I have a wine cooler (for beer) that I want to remote control the lights on by adding a microcontroller. I'm planning on using a ESP32 ...
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1answer
217 views

Circuit for 4-20mA to I2C conversion

Hello I have a circuit that takes a 4-20mA reading from a pressure transmitter and converts it to analog 0-5V then to I2C. But it doesn't seem to be reading I just see about 0.5V on the serial ...
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1answer
61 views

How does I2C Clock Stretching occur on a hardware level

I was reading about the I2C Clock stretching. I understood like, in cases when the slave is requires some time to manage the received data from the master, it slows down the communication speed by ...
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1answer
49 views

On what factors does the I2C pull up resistor values depend upon

I was reading this Article regarding the pull up resistor calculation. I understood that the value of the pull up resistors depend upon the currents, the supply voltage and the Logic Level voltages ...
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72 views

Problem with reading data from I2C Temperature Sensor with stm32

Hi I'm pretty to new to embedded programming and unfortunatly I faced a problem when trying to do an excercise with STM32F103RBT6 Nucleo 64 Board and LPS25HB temperature/pressure sensor. I try to read ...
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2answers
104 views

I2C pin SCL line go to low any random time

In my design i2c have master and one slave communicate with each other. the distance between is approx 1 meter. we put the pull-up register value 10k slave side. they working fine but some random ...
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2k views

Will placing 100 kHz I2C routes below crystal make crystal's output signal too noisy that MCU won't function properly?

I have recently entered into PCB designing area and after reading about sharp rising edges can generate voltage on other components, I was thinking that, in the following image, will the routing I2C ...
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2answers
104 views

Why does the TCA8418E datasheet ask to connect all pins to Vcc using a pullup resistor?

I am trying to use the TCA8418E I2C Controlled Keypad Scan IC With Integrated ESD Protection. On page 3 in the pin functions table it says to connect SDA and SCL to Vcc using a pullup resistor. Do I ...

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