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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How to display I2C address in hex

The I2C communications bus uses 7-bit or 10-bit addressing to address slave devices. Taking the more common 7-bit addresses, each packet sent on the bus by the master starts with an 7-bit address ...
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15 views

Using CMPS10 with I2C interface [on hold]

I am working on a project that i need compass and I have never worked with compass and here I want to use CMPS10 module with I2C interface and also I am using ATMEGA32A Controller. Now i want to know ...
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29 views

Using an i2c i/o expander as input and output

I am using an i2c i/o expander (PFC8574A) with a µC. I am ok with using all 8 i/o pins as input or output, all works fine. Now I would like to know if it is possible to 'split up' the pins...so that I ...
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1answer
37 views

Can sampling I2C influence transmission?

I have 200 kHz I2C communication and I am monitoring it with Logic Analyzer that has 100 kOhm input impedance. When I set sampling rate at 2 Mhz everything looks good on the time diagram. On the other ...
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1answer
54 views

Mixed SPI and I2C using ATtiny USI

I've been successfully using the USI on an Attiny84 to talk SPI to a radio module. This is good for hacking up sensors and whatnot as little radio devices. My next sensor project involves a sensor ...
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1answer
55 views

Will MCP23017-E/SP be compatible with an ATtiny85? ATmega328P?

I mainly want to also be able to use the same I/O expanders with ATTiny85 projects since those chips have limited pins. I will be doing the main prototyping on an ...
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0answers
16 views

i2c of Atmega 328 on arduino uno not working [migrated]

I am using Arduino uno board with Atmega 328 for i2c. The ic is not showing any clock signal on its SCL line on oscilloscope, The same code when used with different new atmega 328, and same code. It ...
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1answer
60 views

why is ground needed to be common in i2c communication?

I'm using i2c for communication between arduino and SBT-150 thrusters , but the problem is that thrusters use 24V and arduino use 5V. So, i want to somehow isolate the two grounds for protection of ...
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1answer
85 views

Voltage regulator like LM 317 which can interface like SPI or I2C

Is there any variable voltage regulator IC similar to LM317 available the output of which can be programmed through a digital interface like I2C or SPI?
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1answer
50 views

TSL2591 sensor value calculation

I bought an TSL2591 breakout board and wanted to write driver for my board. After looking at the documentation, i found that i cannot calculate the illuminance value (in Lux) as their was algorithm ...
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2answers
79 views

Is it allowed to stop and restore I2C transmission?

Is it allowed to stop and restore I2C transmission? I would like to stop it in different periods of transmission and then after for example 500ms restore it to the state when it was stopped. I'm ...
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1answer
75 views

How long/big is an I2C acknowledge?

I'd like to know, how long/big should be an ACK from a slave to its master? I am communicating with a module using the I2C protocol. But the large blank space in the middle, is this an ACK from the ...
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Why the need for multiple I2C ports?

The I2C protocol allows, in theory and with 7-bit addressing, up to 127 devices to be connected to the master. This is a large number, so why would any low-cost microcontroller, e.g. this one, have ...
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2answers
39 views

MPU-9150 (IMU) - what happens at fullscale range boundaries?

We're debating the use of the MPU-9150 IMU in an application. This IMU has a user settable full scale range for the accelerometer (e.g. 2g, 4g, etc) and gyroscope (200dps, 400dps, etc). Suppose I set ...
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1answer
59 views

I2C-controlled digital counter

I need for a project an IC which should generate a digital signal with a length given by an I2C-signal, i.e. if I send the IC "50" (or something similar with the same meaning), I want to get 50 ...
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2answers
106 views

If an I2C device does not appear in i2cdetect does it mean the device is potentially broken?

I am trying to get an I2C OLED (128x64) display working on a BeagleBoneBlack. Unfortunately, no matter what I2C port I try I cannot see the device when using the i2cdetect utility. As you can see ...
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1answer
73 views

Is it possible to connect more than one device on the same SPI?

Is it possible for someone to connect multiple sensors to the same microcontroller's SPI or I2C port? If it's possible, how would someone alternate between devices?
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0answers
59 views

Microchip 9808 temperature sensor - Incorrect calculation result

I am using a Microchip MCP9808 I2C temperature sensor (https://learn.adafruit.com/adafruit-mcp9808-precision-i2c-temperature-sensor-guide/overview). I'm having problems being able to calculate the ...
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0answers
57 views

LSM9DS0's Accelerometer not reading correctly

I have a LSM9DS0 Gyroscope/Accelerometer/Magnetometer breakout board. I am using an Arduino Uno which operates on 5V. The LSM9DS0 is communicating to the Uno using I2C through a Logic Level Converter. ...
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2answers
60 views

LCD 2x16 I2C ST7032i

I write a code using Atmel ASF for SAM devices for LCD 2x16 with ST7032i controller. I've encounter an issue about reading and specifically "busy flag reading". How can i perform read instruction to ...
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1answer
59 views

I/O pin as I2C wire

In my application,I need 2 I2C interfaces as I need to interface EEPROM and smartcard. Can we use I/O pin as I2C wire? How? Is it feasible?
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1answer
273 views

How to make this I2C OLED screen work? (probably SH1106)

I have just received this screen: link but unfortunately it's different then other showed in reviews. That's my version link It's probably based on SH1106 but I can't make it work. I have tried few ...
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4answers
108 views

EEPROM I2C driver hanged during ESD test?

In our prototype , we have a I2C based EEPROM . During ESD Test(High potential spark is injected into system for a very short moment), the drivers hangs in the I2C code. Basically there are while ...
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1answer
52 views

FXOS8700CQ - Arduino core I2C doesn't work, SoftI2C does

I use the Arduino core libraries in my latest project (ATMega328P MCU) I'm trying to talk to an FXOS8700CQ via I2C. Reading register 0x0D should return 0xC7. The typical Arduino Wire library method, ...
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49 views

ATXMega32D4 Two Wire Interface

Lately i have been using ATMega32A and ATMega324PA and learnt various coding techniques in AVR C programming. One such code i wrote is avr_twi.c for communicating with an I2C accelerometer Now i got ...
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1answer
92 views

trouble getting two PICs to communicate via I2C

I'm having a bit of trouble getting two PICs to communicate with each other over an I2C line. Both are 16F886, one sitting in the PIC 28-pin demo board, second one sitting inside a board which I ...
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1answer
51 views

Whats the difference between these three breakout boards for the ADXL345 Accelerometer?

I would like to use the ADXL345 in a schematic im working on right now, but as there is no typical/minimal circuit provided within the datasheet i got stuck. I did a bit of research and found three ...
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103 views

ADC input to raspberry pi - I2C vs I2S

I'm trying to create a microphone array and take readings into a raspberry pi. I'm having an 8 bit ADC connected to the pi via I2C (SCL and SDA pins). I'm able to read samples (0-255) into my pi using ...
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1answer
54 views

SDA line pulled low by slave always?

If due to some problem in slave, The slave is not able to leave the SDA line free , so that master can gain control over it. Its gets low by the slave in between data transfer , but not able to ...
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1answer
126 views

Why is i2cset giving “resource busy” on my BeagleBone Black?

After trying to get Adafruit's 8x8 LED Matrix python example code to work on both my Raspberry Pi and my BeagleBone Black, I realized there is probably something wrong with Adafruit's code and not me. ...
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1answer
97 views

Accelerometer gyrometer for radxa board - i2c configurable addresses vs spi

I am looking for an accelerometer/gyrometer that has configurable address. It should run on a radxa rock board using i2c, or some spi solution. I am using that board (PRO) ...
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1answer
207 views

MPU6050 I2C PIC18F458

I'm using MPU6050 with PIC18F45 protocol I2C. On EasyPIC v6 board its just send me back anything that I put in this WRITE command I2C1_Wr(0xD3);. I replaced the ...
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0answers
75 views

BH1750FVI with I2C won't work

I have the led driver of Adafruit connected to my atmega32. I adjusted their library for the Arduino, so now I just need a µcontroller and not an Arduino. This thing works. Now I want to control the ...
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1answer
82 views

SMBus using Silicon Labs C8051F560

I am trying to communicate an arduino with a Silabs F560 Toolstick Daughter Card. On Arduino (Master) I have loaded the i2c scanner program from http://playground.arduino.cc/Main/I2cScanner which ...
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277 views

What are the options if the I2C slave addresses clash?

Now I have ten accelerator sensors (ADXL345) connected to only one PIC16F887 using I2C. The problem is ADXL345 only has 2 I2C slave addresses configurable. So it brings conflict. I know NXP does ...
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53 views

Power with Battery + 1wire to i2C

I'm creating a project with Raspberry PI B+ where I will get energy from a truck (12~27v) or/and a solar power (6v 5.6w) to charge a battery and keep the device running until the battery finishes or ...
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1answer
73 views

Trying to start i2c communication on dspic33fj128gp802, but I cannot write on the SEN bit of the I2CxCON register

Good evening, I was trying to start the communication with the I2C on my pic. I only set the bits in the control register in the code for now and the inizialization of both the pins and the PLL, and I ...
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1answer
41 views

How does SMBus receive byte command protocol know what to send?

Im programming an I2C device to act as a PMBus slave. Looking at the SMBus protocols (which PMBus is built on) the Receive Byte command has a format described as follows: ...
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1answer
183 views

Multiple I2C slaves on Intel Edison I2C-6 Bus

I've managed to get my hands on an Edison a few weeks ago and have been messing around with the I2C-6 bus and have encountered a few problems. Problem I mainly have sensors on the I2C line. I can ...
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1answer
149 views

I2C protocol debugging using oscilloscope

We are testing an I2C accelerometer connected to the ATMega32A micro-controller. The accelerometer was working fine. We can write and read the registers using I2C protocol. When connected to the ...
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1answer
80 views

Reset I2C slave chip when master goes away

I have a board with a transformer and a MCP23017. This board is connected to another board via 4 wires which bring over power (+5V, GND) and I2C bus for an ATmega328P acting as the master. The ATmega ...
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2answers
359 views

Communication between micro controllers - I2C, SPI, UART?

Basically I have two microcontrollers that I need to communicate with each other. Both controllers send and receive data. Basic idea that I have: I2C, SPI - What I think we can NOT use these ...
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1answer
160 views

I2C: How to adress the second page of a eeprom

I have an eeprom and I can't properly adress everything out of the range 0x00-0x1f. Using the Raspberry I send the following I2C command to the eeprom: "sudo i2cset -y 1 0x50 0x00 0x10 0x29" This ...
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1answer
122 views

i2C multiplexer to use multiple sensor of the same type

I would like to hook up multiple sensor of the same type (temperature, pressure and so on). The problem is that each sensor can only have 2 different unique values for the register, so can't put more ...
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239 views

Controlling LCD with MSP430 via I2C backpack PCF8574

I'm at my wits end with this at the moment. I need to interface my MSP430G2553 with the PCF8574 I2C expander in order to drive an LCD display. So far I've had not much luck at all. There is very ...
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77 views

How long of a wire and how big of a load can I have for SPI bus?

I have a system where I will connect up to 128 identical magnometer ICs up to an FPGA. I am trying to decide between SPI and I2C for comms. If I use SPI the setup will require 128 + 3 wires IF all ...
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387 views

STM32F103 Hangs in I2C_CheckEvent()

I'm trying to connect my both MCU (actually they are two board) together over I2C. one STM32F103ZE (as master) and one STM32F103RE (as slave). This is the code of the Master: ...
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2answers
151 views

I2C Communications with Arduino

My Engineering Design and Development (EDD) class is working on a high altitude balloon (HAB) and my friend an I are in charge of data collection. It looks like we are going to use an Arduino (Uno or ...
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1answer
129 views

I2C interfacing with ATmega32 and ArduinoMega2560 failed

I'm trying out I2C interfacing the ATmega32 with Arduino Mega2560 Board without success. The Arduino Board is configured to be the Master Read. The Atmega32 is configured to be the Slave Write. I ...
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3answers
107 views

I2C Isolation using Switch

In my design I have a controller which is interfaced to the processor (or SoC) using I2C. The processor has internal pull ups for I2C lines so I don't need to put external pull ups. The voltage rail ...