# 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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### Is there a way to use the i2c interfaces on a standard PC mainboard to control a device?

I have attached a few sensors and an LCD display, all of them having an I2C interface, to my raspberry pi, and written a software on the pi to read/write them. Right now, I have a network daemon ...
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### What factors does the set-up time and Hold-time for an interface IC depend on?

I have working with EEPROM and QSPI Flash ICs. They have this electrical parameter called as Setup time and Hold time. I know we must not violate this in order for proper communication. But my ...
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### Wire.endTransmission(); have trouble ending

I am trying to read data from an INA219. To save some memory, I looked at the .cpp file from Adafruit_INA219 library: (Adafruit basically used their function wireWriteRegister(0x05,cal);) ...
61 views

### Different pullup resistors on the same I2C SCL and SDA before and after a I2C repeator hub

My Environment: STM32L476RG RTOS: Zephyr 2.1.0-rc I2C device: AQM0802 (character display 8x2) I2C device: MLX90632 (FIR thermometer) with 1k pullup resistors Problem I am trying to use the AQM0802 ...
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### How to wire 0.91/0.86 inch display to i2c?

I have a 0.91 inch display with a 4 pin I2C connection. I then realised that I needed to use a 0.86 inch display with the connector in the above image. I have searched on google on this but nothing ...
36 views

### Difference between I2C STM32 HAL functions

I'm using I2C in a project on STM32, and i was wondering what's the difference between HAL_I2C_Master_Transmit and HAL_I2C_mem_write, and the difference between HAL_I2C_Master_Receive and ...
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### I2C Master: How to read with repeated start condition?

I have a PIC16F18875, on a board where it is configured as I2C master. 7 bit addressing, 100 kHz clock Several different I2C slave devices are on the bus. am using MPLAB X IDE with MCC plugin using ...
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### Slow FIFO read from LSM6DS3

I have been trying to read FIFO buffer from LSM6DS3 inertial sensor via i2c. The processor will read LSM6DS3 buffer every 20s so the FIFO will contain approximately 3120 bytes of accelerometer data. ...
54 views

### What length wire and how many devices after which I need a repeater or extender for i2c?

I am using an ESP32, which has two i2c buses. I am thinking of adding multiple devices to each bus (a total of 20 devices, 10 devices per bus). The maximum length of any device on a bus from esp32 ...
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### What happens if too many devices connected to multiple i2c buses on ESP32?

See this diagram: In the above diagram, multiple devices are connected to a single i2c bus. In my previous question, I was wondering what would happen if there are too many devices on a single i2c ...
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### How to determine number of devices that can be connected to 3v3 pin of ESP32?

I am not an electrical engineer. I’m experimenting with an ESP32 Dev Kit. I was looking at this image: I had a couple if questions. In this diagram, there are two devices connected to the 3v3 pin. ...
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### Issues reading from an I2C device

I'm testing out the BQ25887 2 cell balance charging IC, and I'm trying to read the data from the I2C interface. But I'm not getting any results. I am unable to see any values from the serial monitor ...
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### Why does my MAX30105 give wrong temperature reading?

I am using a custom made board for the MAX30105 sensor. I am checking with ESP8266 Arduino (Sparkfun max301505 library.) When the sensor is on, the temperature reading is 10 Celcius. It ...
134 views

### Do chained I2C address translators also act as buffers?

I'm working on a data collection/testing setup for multiple pogo pin test PCBs (~10 max per master) connected over I2C, daisy chained together. The design is based around the AD5593R ADC/DAC/GPIO chip,...
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### I2C clarification

This question is mainly to check if I understood i2c protocol and hardware correctly. Because pin modes confusing me a little, ia m jsut a beginner. I2C SDA and SCL lines are pulled high with pull up ...
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### Swapping out RJ-45 connector on Differential I2C circuit

I'm trying to use Sparkfun's Differential I2C Breakout circuit into my own design, and I'm looking to replace the RJ-45 connector. It's too big (having a footprint size of 15.24 mm x 15.24 mm), and I ...
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### what is I2c address of BNO055?

I made a custom circuit with bno055 it shows i2c address 0x70 is it possible? I used the Arduino i2c scanner. I am not getting any data aswell nothing else is connected to Arduino nano board as well,...
18 views

I am trying to control 2 IC(PCA9555) via i2c. The i2c lines can be accessed by a connector. Also i have a usb connector and it is connected to a mcp2221A. The MCP's i2c pins are common with the ...
142 views

### SDA pin on I2C lines seems weird

I am trying to analyze the I2C commands sent by a PC software to R3910 DSP chip The software uses a programming box (provided by the same company that manufactures the R3910 chip) to communicate ...
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### I2C Level-shifting? 2N7002DW

Can someone explain this IC? It seems to be a two-way n-mos (has two circuits in one). I have a master device that runs on 5V and multiple slaves that run at 3V3 and they communicate via i2c. Why ...
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### How does an Intel processor “talk” to an I2C device?

I don't come from an Electronics background, so please bear with me. Assume an Intel processor wants to talk to a temperature sensor over the I2C bus. How does the underlying communication look like? ...
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### What is the difference between SDA protocol and I2C?

A manual for Sound Design Technology's "DSP Programmer" programming box has the following statement: Hearing aids based on the Sound Design Technologies Wolverine platform can be programmed ...
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### What is XCLR and EOC

As the title says, looking at IC9 (BMP085), could someone explain why XLCR and EOC are connected to P-XCLR/P-EOP and why there is no other match in the schematic? Are these connected at all? If not, ...
33 views

### FM4 interrupt only once

I've bought an FM4-176L-S6E2GM board and successfully run the board example projects. Now I would like to modify the s6e2gm_I2S_hp project in order to continually stream a a buffer using interrupts ...
67 views

### I2C bus switches/multiplexer vs analog switch/multiplexer

I'm refactoring a board that needs to switch the communication between an I2C master (M1) and two identical I2C slaves (S1 & S2 with same address). The first design of this board was using a ...
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### PocketBeagle with Midas I2C LCD

I am trying to get a Midas I2C LCD working with a PocketBeagle SBC Linux board. I have tried mainly three different configurations, but none of them seem to work. Connected it exactly as per the ...
133 views

### Spoofing or hiding monitor serial number

A MAC address of a computer can be spoofed by an FPGA which can be programmed as a network controller. I can set a custom MAC address to it. I turn off the motherboard's network interface controller ...
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### I2C on STM8S overstretching clock

How can I fix the super long delay and weird ACK glitch with I2C on STM8S? I'm having some troubles with I2C communications between a raspberry pi and STM8S. The STM8S is a slave transmitter and I2C ...
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### stm32f103 I2C Bare Metal Programming Question

I am trying to send a simple data from STM32f103 to another one. But I am having trouble with my code. I have been working on it since 2 weeks and I couldn't find any solution. I am using PROTEUS to ...
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### PCA9456A i2c switch channel 1 not showing up

I am using an PCA9456A i2c switch to help me toggle between i2c devices with the same address, but i am having problems opening channel 1 (second channel out of 4) and i ran out of ideas what is ...
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### Connect STM32F103 to MPU9250 over I2C with HAL (ERROR)

my experience in programming MCU is only Arduino (also STM32F103 over Arduino) I have now started to use the STM32CUBEIDE and an ST-Link V2 to program my STM32f103. I have tried the functions: ...
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### ESP8266 3.3V and ADAFRUIT TRINKET 5V I2C communication

I try to learn I2C with this diagram as an exercise. I want to read my ESP8266 IO events from my 5V adafruit trinket. I2C MASTER ESP8266ex ...
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### Running out of I2C channels on microcontroller [closed]

I am building a signal acquisition system that has a lot of sensor. These sensors communicate with the microcontroller by I2C interface. I'm running out of I2C channels on the microcontroller. Is ...
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### Using an AXP22x PMIC on I2C instead of RSB

I've got a board with an AXP223 PMIC on it. According to the data sheet, it has an I2C (or TWI, or P2WI, or RSB...) host interface, so the chip is connected to the SoC's I2C bus. The problem I'm ...
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### TCA9509 level translating I2C bus repeater - can levels be the same?

The TCA9509, a nice little I2C bus repeater, has two supplies: $V_{CCA}$ and $V_{CCB}$, for supplying the two sides, master and slave respectively. I can't tell if it can be used as a normal bus ...
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### AtMega328p and TCA9548 problem

I have a custom made PCB that has an AtMega328p MCU and 4 MLX90614 IR Sensors that are being interfaced by a TCA9548 I2C Multiplexer. When I first got my hands on the board I had 10k pull-up ...
84 views

### Infineon PMIC I2C connection for first programming

I want to use the Infineon IRPS5401, a Power Management IC with PMBUS functionality through the I2C protocol. Infineon suggests using the USB005 dongle https://www.infineon.com/dgdl/ug-usb005.pdf?...
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### datasheet register address is not in HEX?

I am reading the this datasheet for the CAP1188 touch sensor and can't figure out what these "register addresses" in the far left column mean. I am used to seeing HEX addresses in datasheets such as <...
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### I2C communication problem with nRF52840

I am trying to make LSM6DSR (STEVAL-MKI194V1) work with nRF52840 DK using TWI Communication. Problem: Firstly, I modified the TWI sensor example to use the accelerometer (LSM6DSR). When I test my ...
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### Touchscreen keeps failing to communicate with raspberry pi, except when I touch the INT pin

I bought a display with a i2c touchscreen from Aliexpress and hooked it up to my Raspberry Pi 3b+. The screen part works fine, however, the touchscreen part is flaky. When I just boot the pi, the ...
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### I2C Bus getting Locked UP on Single Master - Single Slave System

I was trying to develop a I2C driver function for reading data from a proximity sensor(Cypress CY8CMBR3102) and initially the function worked very well and successfully. But while continuously reading ...
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### I2C pull-up to multiple voltage question

Quick rundown of what's going on: I am using two PIC32MX to both be masters of I2C. They will be remotely controlled to determine who is the master at any given moment. Due to redundancy purposes, ...
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### PCB Design - How much length can I2C lines differ by?

I am designing a PCB that uses I2C communication and was wondering how much length the SCL and SDA lines can differ by. EDIT: Clock frequency can be anything from 95kHz to 400kHz. Is there a ...
67 views

### How to chain I²C level shifters?

How can I chain two level shifters in a multi-master I²C system? The following picture shows the I²C bus. Due to low-voltage to the masters, the A side (low-voltage side) of the level-shifter needs ...
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### ESP32 I2C pin routing

I have looked through several documents, but I haven't find found a clear answer which pins on ESP32 support I2C communication. Can the I2C be routed to almost any I/O pins? Are there certain pins ...
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### Is there a way to extend the length of wires for I2C connection? [duplicate]

I would like to connect a BME280 sensor to an Arduino board through the i2c bus connection. I read that i2c was not meant to be used over long wires and will not work properly over 50cm. I want to get ...
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### 3.3V I2C Logic on 1.8V Device

I have designed a board with the ICM-20789, but am having trouble keeping stable voltage values on the I2C bus. Datasheet I have followed the schematic that was listed inside the datasheet, and that ...
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### MCU based I2C master receiver mode includes transmitter mode or not?

If I am programming an MCU I2C peripheral as a master of I2C bus that will be receiving data from other slaves on the bus. So I will set its direction as 'I2C_Receiver.' But since an I2C slave will ...