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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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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 ...
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24 views

DS90UB948-Q1 internal pattern generator

Does anyone have prior experience with DS90UB948-Q1 FPD-Link III Deserializer deserialiser from Texas Instruments ? I am trying to configure the internal pattern generator block sending I2C commands. ...
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Communication protocols

Are the I2C and SPI protocols implemented in the integrated circuits? For I2C, There must be some circuit to be able to process the start bit, device address, internal register Address, Data and ...
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171 views

Problems writing with I2C to registers in Allegro ACS71020

I am wanting to change some of the configuration parameters contained in registers in the Allegro Microsystems ACS71020. I am using an I2C version of the IC. Here is the datasheet: https://www....
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3answers
58 views

Multiple rails I2C bus device from PMIC

I want to use a PMIC chip in my project. As any PMIC, it has a couple of outputs: buck Vout, and an LDO out. The PMIC is operated over the I2C bus. The MCU acts as the host device and runs on Vout, so ...
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62 views

Using multiple TCA9548A multiplexers

The case is that I have 5 temperature sensors. I want to connect 4 of them to the first TCA9548A (TCAADDR0), the SDA and SCL busses (from the ports 0 to 3) and connect the fifth one to the second ...
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327 views

What is difference between UART and i2c [closed]

Why do we need communication protocol and what is the difference between UART and i2c other than clock?
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55 views

I2C multiple masters, one master has internal pull up, do I need external pull up?

I use 2 MCUs as 2 I2C Masters connect with 1 Slave F-Ram to Read/Write data frequency. One MCU has internal 12k Ohm pull up resistors on SDA & SCL. So do I need external pull up resistors?
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48 views

Configuring the clock and LTCD stm32f7

I'm interfacing an LCD using LTDC. That LCD has a touch sensor that works for 400KHz. The touch sensor is interfaced using I2C. My problem is how to configure the clock for both to work. Right now I'...
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2answers
97 views

How to read multiple I2C sensor (MLX90393) data on ESP32? [closed]

I am using MLX90393 Triaxial Magnetometer Sensors for my project. They communicate via I2C. I am using an ESP32 and coding on Arduino IDE. I found this code on GITHUB and was able to read from ONE ...
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67 views

Interfacing touch sensor with stm32f7

I'm having that touch sensor ST IC ST1633i. It's integrated into an LCD. I'm trying to interface with it, but don't know or understand the actual protocol. Here is the protocol So I'm trying to ...
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69 views

Putting a variable of type 'float' on the I2C bus

I'm trying to put a variable that is initially not on the I2C bus, to the I2C bus. However, my variable is of type 'float' whereas the RXData/TXData variables on the I2C bus are of type uint_8t. Do I ...
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46 views

need help deciphering accel/gyro datasheet for i2c communication using python RPi

I have barely any knowledge in this area, the most I have done is used my RPi3 with pre-built python libraries for sensors such as ADS1115 so I didn't have to go through the process of understanding ...
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19 views

STM32091C-Eval: Reading temperature value using I2C Temperatur sensor on the board

I am new as µC programmmer. having dealing with GPIO on the STM32091C-Eval, I wanted to go a step forward working with I2C Interface. On the board i have soldered the SB1 to configure the temperature ...
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1answer
59 views

MPU6050 connection problem

TL, DR: I experience communication breaks while using GY-521(MPU6050 based) with STM32F4 in I2C communication. And looking for the result of these breaks. Also should I give a 5V Vcc or 3V Vcc to GY-...
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86 views

I2C setting MCU as both slave and master at the same time

Hello everyone I'm working on a new project with the TI MSP432P401R microcontroller. I want to have 2 separate I2C buses. I2C bus 1 will set the MCU as the master, whereas the DAC and the pressure ...
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50 views

MSP430 MPU9250 MPU6050 I2C: After sending the address NACK

I have a problem with read from my MPU6050/MPU9250. Both are connected with AD0 to ground so both should have the address 0x68. With both sensors the same behaviour ...
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53 views

Gathering accelerometer data over I2C not updating every 1 ms

I am using an STM microchip to communicate with an IMU over I2C. I am requesting 3 axis of acceleration information from the IMU (x,y,z). I have the ODR Selection frequency set at 1.66 kHz. Currently ...
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1answer
63 views

Removing optimization changes I2C timing

I'm at using SAM E54 Xplained Pro to get temperature readings from a MCP9600 hooked up to a thermocouple over an I2C bus. I'm using Atmel Studio 7 with I2C drivers generated with Atmel Start. I'm ...
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3answers
54 views

What is the difference between a multiplexed bus and a multi-master bus

The jargon of terms in bus architecture literature is half the difficulty in understanding it. At some places the term 'multiplexed' bus is used while at some other places 'multi-master' bus is used. ...
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1answer
60 views

I2C max pull-up resistors and current sink

I design a system with several devices connected to 400kHz I2C interface with wires. For now, I get shark fins instead of square waves, so I decrease pull up resistors value. The MCU, which drives ...
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1answer
37 views

PCF8563 RTC false reading

This my first time to deal with RTC. I forget to add the crystal oscillator to the OSCI of the PCF8563 chip (I thought it has an internal oscillator). Therefore, I had to insert a 32.768kHz (sine wave)...
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319 views

RS-232 to I2C communication [closed]

I'm trying to establish communication between two boards, one of which has an RS232 output and the other with an I2C input. I've looked for adapters online and the only ones I've found seem to be ...
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3answers
89 views

Most significant Bit first Vs Least significant bit first

I am studying protocols and came across a concept of MS bit first(in I2C) and LS bit first(in UART). I couldnot understand the advantage/limitations one has over the other? on what basis is it ...
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184 views

Why HAL_I2C_Master_Transmit always returns HAL_BUSY?

I'm trying to use I2C between an STM32F103C8T6 development board and an Arduino Uno. However, I always get a HAL_BUSY error when I call HAL_I2C_Master_Transmit in ...
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1answer
58 views

I2C in STM32F103 longer data

I am trying to use PCA9539 as an IOexpander for my project. I have a STM32F103 connected to PCA9539 via I2C. The problem I have is to write into PCA9539. Based on the datasheet I should to send (1) ...
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1answer
52 views

Suggestions on wiring PCA9685 i2c + TB67H303 motor ic

I'm trying to design a circuit in order to use the TB67H303 motor driver with the ATMEGA328p and the i2c protocol by using the PCA9685 controller. I never used the TB67H303 and the PCA9685 chips ...
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1answer
63 views

Lighting up LEDS via I2C Bus of a NeoTrellis 4x4 RGB Led Matrix

Many attempts to write to an i2c slave to make rgb leds light up have failed. The hardware in question is found at: https://learn.adafruit.com/adafruit-neotrellis There is an arduino library and a ...
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66 views

Embedded system with hot swapable sub modules

I am designing a embedded system where a master microcontroller (or possibly a SoC) needs to communicate with several different sub modules with a microcontroller of their own. The sub modules should ...
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2answers
71 views

Using higher I2C voltage then MCU supply (but still in limits)

I am working on a project where there is 1x MCU and 2x I2C devices device needs 2.8 V using I2C1 device needs 3.3 V using I2C2 (I have a need of seperating bus apart) If I understand correctly, a ...
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56 views

PCB Ground Plane on Two Layer High Signal Density Board

To give an overview of the design. I am creating a PCB with a header connection for raspberry pi that will use RPI I2C capabilities and GPIO to control board mounted integrated circuits whose outputs ...
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63 views

mcp2221 i2c CLOCK down after ACK

I am trying to control an Analog Devices programming resistor AD5254 by a USB to I2C master device from MicroChip MCP2221. The problem I am facing is that each time MCP2221 is waiting for ACK from ...
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2answers
50 views

ATmega2560 I2C (TWI) assembler configuration problems

I am using ATmega2560 for testing an I2C code. I wrote subrutines in assembler for init, start, write, read and stop the I2C setup. The goal is that master writes 11110000 to a slave with address ...
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997 views

VHDL: What is correct way to model open collector output for FPGA?

I2C uses open collector outputs. FPGAs do not have such outputs. They do have tri state buffers though. How should open collector output be defined in a VHDL for an FPGA? How should open collector ...
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48 views

How does line encoding relate to bus protocols like SPI, serial, i2C, ethernet etc [closed]

I'm referring to line codes like bipolar, machester, miller etc... https://en.m.wikipedia.org/wiki/Line_code How do these line codes relate to bus protocols? Is it another level down? Is it ...
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1answer
47 views

Raspberry Pi I2C with multiple slaves behaves erratically

I have a Raspberry Pi 3B+ that I'm using with two I2C devices on the same bus. The first device is a DAC from Adafruit (product here). The second device is an accelerometer, also from Adafruit (...
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47 views

High speed multiplexing for multiple I2C devices [duplicate]

I'm trying to connect 32 I²C "root of trust" NXP A71CH devices. https://www.nxp.com/products/identification-security/authentication/plug-and-trust-the-fast-easy-way-to-deploy-secure-iot-connections:...
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2answers
71 views

Writing to registers on I2C device

I'm currently working on a side project which uses an SSD1306 128x64 OLED display. I'm then using I2C to communicate to this. However, I'd like to better understand what exactly is going on when I'm ...
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1answer
51 views

Can an I2C switch control multiple I2C switches?

I was wondering if I am able to treat an I2C switch simply as another I2C device and use 1 switch to control more switches downstream. This picture below shows what I am trying to do.
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1answer
57 views

Why are input and output of I2C voltage level shifters connected?

Below is a schematic for a board from ST for testing VL53L1X sensor. It converts 3.3V to 2.8V internally because the sensor's recommended operating voltage is 2.8V. The green lines are SCL and SDA ...
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97 views

PX4FLOW (Optical Flow sensor) - Powering with 5v. Does it work with OmniNXTF7 I2C SCL/SDA at 3.3v?

I want to use PX4FLOW with OmniNXTF7 flight controller. This flight controller has 3.3v I2C SCL/SDA and no PullUp-resistors. I use the PX4FLOW only with I2C port, with 5v at VCC (not 3.3v). Does ...
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1answer
88 views

Connecting up to 32 Devices I2C

I'm trying to connect 32 I²C "root of trust" NXP A71CH devices. I'm thinking about a good way that does that, I mean what kind of communication should I use? A digital multiplexer that selects a ...
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60 views

Altium: Repeating SPI/I2C Blocks

What is the proper way of repeating I2C/SPI blocks? Since we know in the case of SPI blocks, MISO, MOSI & SCK must all be tied together in a single bus for communication to happen. I have read ...
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1answer
36 views

Is DS28EC20 (20Kb 1-Wire EEPROM) a secondary address of I2C?

I have a MCU (nucleo64 L476RG), connected with I2C, and I2C is connected with DS2482-100 (Single-Channel 1-Wire Master), then to a DS28EC20 (20Kb 1-Wire EEPROM). I create project from stm32cubeMX and ...
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0answers
146 views

Strange I2C communication

I am currently trying to test the SHT3x series humidity sensors by Senserion. I have their EK-H4 evaluation kit to get data from the sensors. I can plug in the sesnsors provided with the kit, and all ...
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2answers
146 views

How to find I2C address of DS2482-100?

I am using stm32cubemx to create an I2C project. I am using nucleo64 L476RG to connect with I2C ds2482-100, and another 1-wire DS28EC20 is connected with I2C. I am very new to this project. The first ...
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2answers
120 views

Extremely low data rate transmission over long distance for attinys

For a lighting project I need to be able to trigger 20 units every couple of seconds independently which are daisy chained with 1-2 m space between each of them like so: Control station ====== Unit 1 ...
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2answers
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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60 views

How to properly implement I2C communication between two or more STM32s?

I have a master board with STM32F030R8 and two daughter boards with STM32F030C6. The objective is to communicate parameters between the boards periodically and also on-demand. With some effort I ...
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67 views

Long-Distance Multi-Slave Communication

I am currently trying to connect many serial slave devices to my Arduino device over a 14 meter distance. I am looking to have slave-to-master communication. These devices include: 3 BME280 ...