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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USB Audio Stream to Codec

I have been trying to design a USB Audio Interface with an Atmel SAM3U microcontroller and I think I have hit a wall in my thinking process. As a sidenote, I'm relatively new to the world of ...
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Arduino: What is the best way to send and receive data with I2C?

I am using I2C to send and receive int values from a RaspberryPi to an Arduino then echoed back to the Pi. The primary problem I am having is with int values larger than 255. A secondary problem is ...
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Can I do without I²C pull-up resistors?

I am trying to produce a small circuit, and I am looking to reduce the part count. I recently added an I²C EEPROM which is used once when the system boots up, along with this EEPROM I added two ...
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Lockup while evaluating Wire.requestFrom function (Arduino) [migrated]

I am currently working on a Arduino project that combines an InertiaOne IMU sensor board (from Atmel), with an Arduino UNO and two motors driven by a Makeblock driver board. All sensors communicate ...
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Is it safe to not power this USB to I2C chip when USB isn't plugged in?

I am working with someone on a data logger based on an MSP430. Since it operates on battery power, we want the device to use as little power as possible. We are planning to use this chip (FT201X) to ...
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2answers
221 views

Can I use 74HC14 or NPN transistor instead of MOSFET as level shifter

I have SN74HC14 or BC548 / 2N2222 transistors. I need level shifter for I2C between arduino and RPi. Here's simple circuit from the internet Problem is I don't have any MOSFETs. Can I use NPN ...
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1answer
79 views

Porting Linux drivers specifically I2C

I am developing an I2C driver for an accelerometer. My objectives (actually it's the restriction I have as per the project guidelines given in my institute): use Linux flavour of operating systems ...
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1answer
23 views

AVR TWI Status Codes Complete List

Can anyone provide a link for complete list of status codes for AVR TWI? I am working with DS1307 using TWI, during which at some point I receive a status code of 0x40. However there is no mention ...
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18 views

I2C 2 way communication between Arduino Uno and Arduino Mega [migrated]

if I remove the transmission code from slave this works properly but I need to transmit from slave. Here is my master code ...
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1answer
188 views

Arduino Uno to ATtiny44A I2C communication

I tried to make I2C communication from Arduino Uno to ATtiny44A. Uno as Master and Transmitter code: ...
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2answers
88 views

How to drive a single 7 segment display with I2C?

I am looking for a solution to drive a single 7 segment display with I2C. I found some websites that shows 2 or 4 digits with I2C but I didn't find a solution for driving a single digit. I'm making a ...
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39 views

MMA8453 accelerometer I2C problem

I ran into an issue with my project. I use Renesas RL78 microcontroller and on one I2C bus I have two sensors: digital compass and accelerometer. Accelerometer type is MMA8453 by Freescale. ...
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310 views

I2C actually sends inverted data over the line?

It seems to me that I2C is actually transfering inverted bits which sounds a bit odd so I am seeking for a clarification. I2C diagram from here. Let's say we are writing to slave. A zero (0) comes ...
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57 views

Writing to register on I2C device, returns device busy

I am trying to write data to a register on an I2C chip from the Raspberry Pi, when I use i2cdetect I get UU, which I understand is an error. ...
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2answers
41 views

How does multimaster I2C work and its significance?

I am fine with I2C basic communication and implementation? Need info on Multimaster mode of I2C How does multi master I2C work? Advantages over I2C single Master? In what circumstances this multi ...
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2answers
56 views

Arduino I2C and multiple devices

I have created two projects, one with a Tiny RTC and another one with the BM180 sensor to read barometric pressure and temperature. Now I want to combine both. I'm trying to connect both - the ...
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4answers
141 views

Connecting a 9V IC's I2C interface to 3.3v Arduino DUE

I need to connect a TDA7312 to Arduino DUE's I2C interface via SDA/SCL. TDA7312 operates on 9V, Arduino DUE is 3.3v. Is it possible to safely connect it, without burning it? Or what should I use ...
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2answers
113 views

Reason for choosing SPI based flash devices over I2C ones [duplicate]

I have gone through the below link which says that u-boot support three type of flash technology http://www.stlinux.com/u-boot/flash 1.Nand 2.NOR 3.SPI Serial Flash I would want to know why SPI is ...
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2answers
66 views

I2C Enabled LCD Unreliability

I'm trying to control an I2C Enabled LCD Display using the STM32F0. I have a bunch boards built with the LCDs and a couple of them work all the time, a few work intermittently and a few rarely work at ...
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47 views

Combine protocols on a U/FTP Cat 6a cable (USB 2.0/I2C)

Main question Can I use a Cat 6a cable for USB communication? On the cable it says 650 MHz, is this sufficient for USB 2.0? The length of the cable would be about 6 meters (about 19 ft). If so, would ...
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1answer
64 views

How to read SAA1064 7-segment values

I have a central heating system that displays it's info and error codes on 4 7-segment displays. These displays are driven by a SAA1064, like so: This SAA1064 (datasheet here) receives it's ...
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2answers
65 views

Serial comms over 3m cable, shared with USB

I am designing a system that needs to do serial comms over a standard USB cable, as well as normal USB (but not at the same time). In other words, when plugged in to a PC it will appear as a USB ...
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1answer
58 views

I2C - connecting 5V device to 3.3V host

Is it safe to connect any 5V I2C slave device to 3.3V host? I know, that DS1307 realtime clock can be connected to Raspberry Pi (3.3V IO), because DS1307 just pulls down data lines and 5V voltage ...
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70 views

BSS138 levelshifter draws 35-40mA current when one side is grounded?

I completely rewrote my question as I found the source of the issue is related to the level shifter only. This is the circuit for a 3.3V to 5V bidirectional levelshifter, used frequently. My ...
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55 views

Bosch BMI055 Accelerometer/Gyro causes I2C bus to crash when issuing a softreset!

Datasheet: http://ae-bst.resource.bosch.com/media/products/dokumente/bmi055/BST-BMI055-DS000-06.pdf I have recently integrated the Accelerometer of the BMI055 I added a soft reset of the chip at ...
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161 views

Best way to do I2C/TWI over long distance

I have a project that requires to do I²C/I2C/TWI over a long distance (30 to 40 meters). I've seen some people suggesting lowering the clock-rate to somewhere around 500 Hz, to mitigate the effects of ...
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1answer
89 views

AVR TWI (I2C) problem

I am using ATmega32A and 24c16A EEPROM for testing an I2C code. For every state transition, controller responds by changing the status register TWSR. After start ...
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3answers
273 views

Can I use both I2C and SPI at same time with PIC16F1503

Im new to Microchip microcontrollers and I'm looking for very low cost device with I2C and SPI. I want to connect one I2C (ADC) and one SPI device (LCD). I found this very low cost device: However ...
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59 views

GY-521 Unable to set PWR_MGMT_1 register - can't disable SLEEP mode

I am attempting to interface between a custom 8051-based MCU and a new (ebay) GY-521 module (Gyro/Accel chip) using I2C bus. I have written the I2C bit-bang functions myself and they seem to be ...
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1answer
63 views

SWD and i2C hardware layer differences

Both I2C and SWD are two-wire protocols. I wonder what are the main differences of the hardware layer of these protocols and what are the pros/cons of each one? It's also interesting that the maximum ...
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Sending I2C reliabily over Cat5 cables

I am considering implmenting an home automation system around my Raspberry Pi but I found the price and space requirement of inserting a Pi every place some control is required too much but the Cat5e ...
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2answers
142 views

How to avoid short circuit when connecting a microcontroller and device using I2C bus?

I am attempting to connect an 8051-compatible microcontroller to an accelerometer using the I2C bus. Both devices operate at the same voltage, 3.3v. However, I am failing to understand something: ...
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1answer
124 views

Can I2C bus be left open circuit?

While trying to make a TV tuner radio like I saw here I got myself a I2C PLL Tuner from an old TV and powered it up without connecting I2C bus lines to the circuit. Not even to the pull-up resistors. ...
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1answer
44 views

help with QT1070

I am using AT42QT1070 touch IC in comms mode with I2C communication.I have used 10k pullups with SDA and SCL line and 47k pullup with CHANGE line(active low) as mentioned in datasheet. The CHANGE ...
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2answers
480 views

What do hardware address pins do?

I have been delving deep into digital logic and am trying to understand some memory architecture basics. I have started looking at data sheets to get a grasp on some real-world components and noticed ...
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5answers
148 views

Maximum I2C Bus Length?

What is the maximum length of cable that could be used to connect two I2C devices (I2C master-> I2C slave)? Yes, I know that I2C is really designed for intra-board communication. I have been tasked ...
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1answer
52 views

NXP i2c temperature probe locking up

I have an issue with an NXP SE95 temperature probe that has been working just fine up until now on other systems. At some point, either on boot or soon after, the probe will have some sort of meltdown ...
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2answers
103 views

Unpowered devices on I2C/SPI bus

I'm trying to develop a board that includes I2C and SPI devices that are unpowered for the majority of the time to save power. I found that for these particular devices (Honeywell HSC pressure ...
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1answer
130 views

Problems with I2C on PIC18F25K22

I've been googling for about two weeks now and I still can't seem to get my I2C working. I've used this (what seems to be complete) tutorial. I followed the Master Write and Master Read examples to ...
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1answer
175 views

Problem using DS1337 - RTC

I am trying to use a edited version of the library given at this link. I basically changed some of the included file and some of the changed function of the wire.h library. Though I am not a hardcore ...
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0answers
89 views

I2C Reading START STOP but nothing else

I am working on getting a LED driver (pca9635 - datasheet ) to work with a PIC32. Below is my code ...
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2answers
132 views

I2C General Call Confusion

I'm trying to understand how the I2C "General Call Address" is supposed to work for implementing in a microcontroller. According to the I2C Specification (PDF), Section 3.1.13: When bit B is a ...
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1answer
34 views

I2C access on M41T00CAP RTC device

I am trying to access "M41T00CAP RTC" device through I2C. there are other I2C devices also, which I am able to access perfectly. but in case of RTC device , I am not able to read the register ...
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1answer
108 views

Relationship between clock speed and I2C bus speed

I have understood how the I2C protocol works. The I2C protocol specifies three modes, namely 100kbps (original speed), 400kbps (fast mode) and 3.4 Mbps (high speed mode). One thing I didn't understand ...
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52 views

MCP23017s and arduino problems

I'm not native English speaker, so forgive me my bads. Ok. Here's the deal. In my Arduino UNO I need more outputs and inputs. I bought 3 MCP23017s. One of them for receive states from 8 ...
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137 views

What is purpose of zener diodes in this circuit?

I am reading the I2C tutorial: https://learn.sparkfun.com/tutorials/i2c/all Why wouldn't it work without the zener diodes? What functionality are they adding? They are just there to keep the voltage ...
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112 views

Bit-banging I2C question

When bit-banging I2C using 2 PIO lines do these lines still need to be pulled high? Obviously using a dedicated I2C bus the lines must be pulled high as the pins are open-drain outputs but PIO pins ...
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1answer
104 views

bitbanging i2c problem with ACK from slave

I am trying to implement bit-banging i2c to communicate between an atmega128A's GPIO and an SHT21 (I2C bus was used for some other devices). The first task is to send a write sequence to the SHT21. ...
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3answers
542 views

How is the clock frequency established between master and slave in I2C protocol?

This is a follow-up question to What happens if I omit the pullup resistors on I2C lines? In a digital wall clock I designed (using the DS1307 RTC and the ATmega328 MCU), I accidentally omitted the ...
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2answers
131 views

Select channel from multiplexer to show temperature values in c programming

I have question regarding selecting channel from multiplexer. I'm trying to receive some temperature reading from the two sensors which shared the same address and while I'm using one sensor, it can ...