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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Data send only in MCU based I2C Slave

I want to know that is it possible that a Slave I2C device which is a 32-bit MCU, for example STM32F407, I write its I2C data send function and send data through it after every 1 sec? I am asking this ...
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Increasing system clock frequency on STM32F303 drops I2C clock proportionately - why?

I'm trying to figure out a weird little issue I've discovered while debugging another element of my code. I've got a STM32F303K8 reading and writing to an I2C peripheral. The I2C clock speed is ...
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1answer
53 views

Large delay between I2C messages on STM32F303 - trying to read as fast as possible

I've got a sensor that I'm reading via I2C. My end goal is to be able to maximize the rate at which I can take these readings. In order to read, I have to write an zero-byte I2C message to the slave ...
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56 views

MCU to MCU I2C communication

I have 2 MCUs and I want to connect them together over I2C bus. MCU1 will be Master while MCU2 will be Slave. Only these 2 MCUs are on the bus. This configuration is fixed and I cannot change it. ...
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35 views

I2C Problem in TCA9539

I am using stm32f103 and TI's TCA9539 and TCA6408A Port extender.Both of them support 400-kHz(I2C Fastmode) and 100-KHz (I2C standard mode) clock frequencies. I use 3 TCA9539 and 1 TCA6408A;here is my ...
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USB HID Keyboard controller chip needed [on hold]

I've googled myself silly without result and I'm hoping someone can help! My goal is a single chip with a USB interface on one side that acts like a HID keyboard device. On the other side any MCU ...
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24 views

Bit Bang SCCB Issue

I am trying to bit bang an SCCB communication between an OV7670 camera module and an STM32F407 Discovery Board. In the datasheet, it is stated that the slave write and read addresses for the OV7670 ...
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27 views

OTI-301 Infrared Sensor

I built an infrared thermometer using the MLX90614 IR sensor and an Arduino Nano. I needed a little higher temperature reading so I changed to the OTI-301 sensor hoping that it would work with the ...
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2answers
41 views

Slave can't pull I2C low

I'm trying to use 3 TCA9539PWR and a TCA6408A on an I2C bus. Here's the schematic diagram: However, when I try to send the TCA9539PWR's addresses , none of them responds (no ACK) and when I try to ...
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HAL SCCB Commuincation via I2C: HAL_ERROR Status

I am using an STM32f4 Discovery board to interface with an OV2640 Camera. When attempting to set the SCCB registers, I am using I2C. However, when doing a simple test I cannot connect to the device. ...
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Custom 12 V DC motor control with ESP8266 without PWM

Scenario (you might want to skip the lengthy back-story) I'm trying to integrate my home ventilation system with my home automation. It currently consists of ten fans with ceramic heat recovery ...
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Order of I2C signals on the header [duplicate]

I am wondering are there any standards for the order of signals on I2C header? We get many I2C devices on the market, but the order of pins on the headers is inconsistent and hence we may not be able ...
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63 views

EEPROM Read Operation Always Returns 0xFF

I'm working with a AT24C04 EEPROM which communicates with a LPC1768 MCU on a I2C bus. I try to write a 8 bit data (0xF0) on the 0x00 Address of the memory but when I want to read the content of this ...
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Is the SCK line in I2C unidirectional or bidirectional?

I've always considered SCK to be a unidirectional line since the master generates/transmits the clock signal and the slaves "see" the generated pulses. I have found many sources that agree with this ...
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Connect I2C Oled via USB to Linux Box [duplicate]

I connected a 1.3" SH1106 Oled via the I2C pins to a i2c-to-usb adapter (UMFT201XB from FTDI) and on my Linux Box (Z83 mini pc with Ubuntu 18.04) I can see the device under /dev/ttyUSB0. This is the ...
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73 views

Connection between 3v3 and 5v I2C without have a reference voltage

I've two board that must communicate trough I2C BUS. One operates at 3v3 and the other one at 5V. I unfortunately can't use a reliable level shift IC becouse the physical connector on the board share ...
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PIC16F7X I2C Issues With 24AA01/24LC01B EEPROM

I have an existing PCB that is no longer supported by the manufacturer and has been plagued with software issues for years. So i don't have much control over how the board is laid out and what ...
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1answer
37 views

stm32f0 sht35 i2c communication failure

I need to read temparature and rh values from sht35 sensor. here is the datasheet I am using stm32f0 and I have 2 different sensor. problem keep occurs with both sensor. Address pin connected to the ...
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60 views

Why is the ADDR flag cleared without reading the SR2 register?

I am doing I2C project with MPU6050 using STM32F4DISCOVERY board. The ADDR bit in SR1 register is clearing in one instruction execution without reading SR2 register. Because of clearing ADDR bit, I ...
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1answer
59 views

Master SW (bit-bang) I2C with Interrupts?

I've written a set of "bit-bang" software routines for the PIC18F2620 device. These routines work well for reading and writing 24LC256 EEPROM and DS1307 RTCC devices for the most part. (I wrote this ...
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1answer
31 views

FIFO Clock Setup for CMOS Detector

When attempting to construct a miniature laser beam profiler with the Omnivision OV7740 CMOS detector and an Arduino Due, I am running into some problems with FIFO reading/writing. From the datasheet, ...
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51 views

I2C and separate power source affects SDA signals

Despite the fact that I2C devices should be able to operate with different power sources I'm having problems with my setup. Specifically, it seems that when I have separate power sources the SDA ...
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2answers
48 views

Using multiple sensors on the same i2C circuit

It’s possible to control multiple pH probes with one single i2C ph circuit (like this https://www.atlas-scientific.com/product_pages/circuits/ezo_ph.html) ? Rather than buying I2C circuit for each ...
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1answer
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LSM303CTR 3-wire SPI and I2C - conceptual problem

I'm trying to interface LSM303CTR e-compass from ST-microelectronics with microcontroler. Due to design limitations I have to use 4-wire SPI. This MEMS device has option to switch beetween 3-wire ...
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31 views

STM8S005K6 - I2C (Bus always busy)

This question has already be posted but i don't find a solution of my problem. I have an LCD screen (MC20805A6W-BMLW-V2) with I2C communication and I try to communicate with my controller via I2C (...
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APDS 9900/9930/9960

I am trying to write a program that detects up/down and left/right gestures from a gesture sensor using atmega32a. I can't actually read the LEDs and the sensor been used is the APDS 9900. This is ...
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1answer
65 views

Which pins support i2c protocols?

I have a ESP32-WROOM-32D , it support I2c protocol but when i refer the i2c pins(SDA,SCL) in datasheet ,i couldn't find . datasheet is given below. which pins that support i2c protocols? ...
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Can I use I2C over 2m cables?

In my current project, I need to communicate between a microcontroller and some sensors over I2C. One of them is a temperature sensor, it needs to be placed at approximatively 2 meters far from the ...
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1answer
44 views

Unable to read data from MCP9808 using i2c

I have a MCP9808 temperature sensor and a Raspberry Pi 3B plus. I had great success reading the temperature from this sensor via i2c on an Arduino Uno, but am not able to read the temperature with ...
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why i2cdetect -y -r 0 cannot detect all my device under /sys/bus/i2c/devices/i2c-0/

i2cdetect -y -r 0 only shows a 0x70 address. But it show has one more 0x6f address: ...
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1answer
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Need smaller pullups on i2c lines, but design is low power, what is best?

The pullups on my i2c lines are 4.7k. People are afraid of draining the battery by fixing this waveform with smaller pullups, like 2.2k. It doesn't seem much power is wasted considering the short ...
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mpu6050 returns zero, I2C stm32f103

I am working with MPU6050 and STM32f103VE as master. When I wake up the sensor and ask for information it returns 3 bytes of zeroes and the protocol stops working. I only send the communication Part ...
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1answer
127 views

Strange “step” in i2c plot [closed]

I have some errors during debugging I2C chip. I took an oscilloscope and found some strange artifacts on the log: Maybe somebody has a suggestion about such questions? 1. What are these strange ...
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Need a solution to sent i2c data long distance (prefereably convert to CAN)

Is there any IC available that can read I2C data from a sensor and convert to CAN. I was looking for a low-cost solution to reading i2c data and putting it on a CAN bus. Reading i2c with a ...
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3answers
130 views

I2C noise from 433MHz transmitter

I have built a little thermostat based on BMP280 temperature sensor over I2C, ESP8266 Lolin v3 and STX882 433Mhz transmitter. I have not added additional pull-up resistors or decoupling capacitors. ...
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1answer
67 views

Combine two 8bit EEPROM to make 16bit EEPROM

I am working on building a computer out of logic chips. I want to use an EEPROM as the instruction memory. However, my EEPROM's only has 8bits data output, but I want my instructions to be 16bits long....
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Help with I2C Communication

I'm trying to learn how to program a battery charging IC (BQ24193) via the I2C communication protocol. My goal is to write the correct values to it in order to gain the proper charging input and ...
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1answer
62 views

Help with understanding the Memory Map of MLX90393

(Using a Raspberry Pi 3 Model B+ and python) I needed some assistance in understanding the memory map of MLX90393 I've attached the memory map here and you could also find it in the datasheet. I'm a ...
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40 views

Two-way communication between esp32s

I am planning a circuit that requires two-way communication between one esp32 and 3 others. I want to use a master/slave architecture as shown here: They need to be able to communicated via hardware, ...
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0answers
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IR Temprature MLX90614 Sensor Diffrent behavior based the I2C Scanner Checking

I need to work with Temperature MLX90614 on Arduino, when i used it's default library code, in bread board sometimes i get correct answer, so i used the soldered circuit for it like this: in this ...
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1answer
72 views

STM32 trying to communicate with 2 I2C. But second one fails

I am trying to communicate with a battery using SMBUS. Battery has 2 sections so it uses 2 separate SMBUS lines. I am trying to read SOC information from two section by using STM32F103C8. First ...
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2answers
79 views

i2c multi master “undefined conditions”

I have read the I2C bus specification and don't quite understand the limitations of a multi master I2C bus mentioned on page 10: https://www.nxp.com/docs/en/user-guide/UM10204.pdf One the one hand ...
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56 views

STM32 I2C Fast Mode Issue

Currently, I am implementing I2C communication with Interrupt. STM32 serves as the slave and Arduino serves the master. MCU: STM32L152RDT6 For previous work, I2C communication in standard mode is ...
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38 views

Any side effects of Initialisation and de-initialisation of STM32F0 MCU I2C pin frequently? [closed]

I have one port on my MCU and want to re-define its functionality. Is it possible that something wrong/strange happens if I do it in my main() function? I regularly ...
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1answer
50 views

STM32 I2C transmitting no data and cannot change the data that is being transmitted

I am trying to establish a SMBus connection by using STM32 chip. When I try to transmit data to battery (0x0D) I see 0x0B with oscilloscope. When I change the data that is being transmitted to 0x00 or ...
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3answers
105 views

I2C bus communication Issue

I have connected 3 sensors and they are connected to the I2C line of ATMEGA2560 as shown in figure. In normal condition, they are working fine and providing accurate sense value. But, when one of the ...
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1answer
108 views

Does the drive strength of a GPIO pin alter with change in temperature?

In low temperatures the functionality of the I2C is being affected, but the slave is working properly and the temperature is also within limit of slave. For that reason I suspect the drive strength. ...
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1answer
77 views

What does Pass through I2C mean?

On page 3 of this app note the following is said Pass Through—This I 2C control enables communication with all the remote devices, whose device ID and corresponding device Alias fields is ...
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1answer
216 views

Allegro ACS71020 problem interpreting I2C data

I've added an Allegro ACS71020 to my Arduino project to measure power usage (circuit shown below). I can connect to I2C on 0x63 and I get response (check the image below) - but the values do not ...
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2answers
72 views

RPI-arduino communication without UART

I'm working on a project where a raspberry pi zero will be the main controller. The pi has to receive information from a GPS module (gy-gps6mv2) over UART. The same pi will be controlling (receive and ...