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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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41 views

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 ...
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60 views

I2C Multimaster Operation

This is with reference to this question and this App Note In the App note, Page 4, it discusses about the steps for multimaster which I have mentioned it below : " The following describes the ...
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31 views

I2C bus arbitration - communication layer

I want to understand about the communication layer on which I2C Bus arbitration is done. My question is based on this question which was previously asked here. The accepted answer states that Bus ...
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66 views

I2C PCB Layout to connect 3.3V and 5V Sensors to Raspberry Pi using a Logic Level Converter

I am creating my first PCB Layout to connect 6 Sensors via I2C to my Raspberry Pi. Four Sensors are running on 5 V and two on 3.3 V. That's why I am using a logic level converter to get them ...
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NXP PCA9615 I2C differential buffer - failure on SCL line

I am using the PCA9615 part to extend an I2C bus. The PCA9615 converts I2C to a differential bus. PCA9615 https://www.nxp.com/docs/en/data-sheet/PCA9615.pdf There is a control box and a remote ...
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2answers
45 views

I2C Communication Open drain benefits vs Push pull

I am reading this TI I2C App Note for understanding the I2C operation and need to understand how Multi master I2C will operate. I was not able to understand this para in the app note, "Since no ...
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963 views

How to end sending data over I2C by Slave or Master?

Let us say a Slave or Master is sending multiple bytes to the receiver on I2C bus and the number of bytes is not defined before hand. So then how will the sender tell the receiver that it has no more ...
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2answers
61 views

I2C data sampling is done at clock edge or level

I am trying to understand I2C data bus from this document. It explains the START-SLAVEADRESS-R/W-ACK-DATA.. as the master-slave take turns to get hold of the shared bus for mutual communication. One ...
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I2C High Speed Multiple Slaves Layout

I am working on a system where I need to have 16 I2C devices on one bus. Due to data rates I need to run at 3.4 Mbit high speed mode. Are there any design/layout guidelines to help deal with a large ...
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109 views

Texas Instruments Page/Register Convention - how to find the actual register address?

I am having troubles understanding TI datasheets regarding their DACs... I haven't felt so stupid for quite a while! To make things as transparent as possible, here is a very literal question. I am ...
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30 views

how to power cycle i2c sensors in battery enabled systems that enter deep sleep

I am looking for a way to power cycle multiple i2c devices that are connected the same i2c bus, having an ESP32 mcu as a master, in case the i2c bus hangs for any reason. The circuit has a lipo ...
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2answers
41 views

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
67 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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1answer
61 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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3answers
132 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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37 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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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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28 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
42 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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19 views

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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44 views

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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2answers
47 views

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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140 views

I2C Communication Between STM32F3 and SSD1306

I am trying to write data to my 128x32 OLED display. I researched it online and found that it has the SSD1306 controller connected to the display. It uses the I2C protocol and it only has 4 pins (VCC, ...
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65 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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824 views

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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3answers
130 views

I2C device lists 20mA max current on AD, CL, and DA pins. Do I need a resistor between it and Arduino?

I'm looking at the datasheet for an LED controller (the MAX6955), and it shows that all of the interface pins; clock, data, address, etc., have current maxima of either 20 or 40mA. I'm aware that the ...
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1answer
58 views

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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2answers
4k views

STM32F4 HAL I2C only sends address

I am working on a project where I need to set a simple LCD. This LCD use the 'ST7032i' chip to control the LCD. I want to control the LCD over an I²C interface. As controller I use a STM32F4 ...
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1answer
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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1answer
215 views

MAG3110 and MPU6050 on one I2C bus connected to a Raspberry Pi

I am trying to use separate pre-built breakout modules containing a MAG3110 (Magnetometer) (module) and a MPU6050 (gyroscope) (GY-521 module) on one I2C bus connected to a Raspberry Pi. Although both ...
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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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25 views

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
60 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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2answers
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
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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1answer
160 views

Slew rate limiting of bidirectional lines

Assuming the ICs in use don't offer an adjustable slew rate, if I want to limit the slew rate of a unidirectional digital data line, for example of SPI's MOSI-signal, I can put a series resistor at ...
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52 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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1answer
245 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
49 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
92 views

I2C transmit & receive between ALS OPT3006 & 8051

I'd like to ask for solution to let the microcontroller (MCU) get data from ALS (ambient light sensor).I'm wondering why my MCU can't get ACK (acknowledge signal) low? In this program I have 2 ...
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1answer
19 views

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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34 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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4answers
202 views

I2C Arbitration lost on ATtiny85

I'm new to I2C and am trying to get two ATtiny85 to talk to each other. I have Arduino IDE 1.8.0 I used this link (damellis) to install the ATtiny board in the IDE I use an Arduino nano to program ...
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22 views

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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5k views

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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4answers
2k views

Implementing an I2C buffer in C

I'm implementing a read-only I2C slave on a PIC18F4620. I have made a -working- ISR handler for the MSSP module: ...
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3answers
526 views

LCD interfacing Issues: Embedded Systems

Hobbyist tend to use parallel communication for interfacing with an LCD and all the libraries are for a specific type of microcontroller (Arduino or AVR) or LCD. But, for a design engineer, it is ...
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2k views

Is there an I²C device out there for reading a set of PWM inputs?

I'm thinking about getting a bunch of Maxbotix Ultrasonic rangefinders. I'd like to use as few pins on my controller as possible. Since I don't think you can have multiple devices on an RS232 serial ...