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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Sensible standard wiring type for long-range I2C

I'm planning on interfacing with some sensor devices via I2C over a long bus, with devices chained every 2m or so, up to 16m in total. I've seen other questions here referring to this from the "which ...
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23 views

Control LCD with TIP121 on Arduino not displaying anything

I'm trying to control the power of an LCD I2C display. My project uses and Arduino and LCD, but when Arduino goes to sleep, the LCD stays on. So, to solve this problem, I connected a TIP121 transistor ...
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19 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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44 views

I2C level converter stops bus [closed]

I am trying to get an lcd 16x2 with PCF8574 I2C working with my arduino due. If i connect my lcd with 3.3v (backlight doesn't work, led from the PCF8574 lights up) and upload the i2c scanner sketch ...
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43 views

i2c communication between cc3200 and at42qt2120

I am trying to do i2c communication between TI's cc3200 and atmel's touch IC AT42QT2120. I am able to read and write to different memory locations of the touch IC, but i am unable to get it's change ...
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83 views

Connecting i2c slaves to master over RJ45 style cable?

I'm desigining several modules (e.g. sensors, motor controller, etc.) that need to communicate over I²C. These modules can be up to 15ft (5m) away from the base module (I²C master - Spark Photon) - ...
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32 views

CSI/DSI over one meter cabel

Imaging you have a smartphone where the display and the camera is attached with a one meter long cable. What would be the best and most power efficient way to transfer camera (CSI/I2C) and display ...
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24 views

ADXL 345 Noise Issue for my use case

I am building a solution where I want my MCU to wake up based on a trigger generated by accelerometer after detecting an activity. There are a number of samples available for this and I am able to ...
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2answers
74 views

Cheapest way to get a CAN signal

I have to transfer signals over around five meters. My input signals are I2C or SPI-compatible, but unfortunately it is no good idea to transmit them over such a long distance. Therefore I was ...
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1answer
46 views

Adding High Byte and Low Byte of LSM303DLHC Accelerometer Output

Interpreting LSM303DLHC Accelerometer Output Hi all, This is my first StackExchange question ever, so I will do my best to be specific and offer as much reference as possible. I'm currently ...
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3answers
200 views

How to achieve 57 PWM outputs most easily and cheaply

I need to light up 19 RGB LED strips, which it seems would require 19*3=57 PWM outs and 57 transistors. The transistors aren't an issue, but of course the 57 PWM's is. Most micro controllers simply ...
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39 views

Does SMBus spec lie about I2C?

In the SMBus spec it says: The I²C specifications do not require that a device always acknowledge its own address. This can confuse a system controller. If a device does not acknowledge its ...
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91 views

LMP91000 I2C Write Problem

I've posted this question to TI E2E forum here. I'm cross-posting it here in hopes of casting a broader net. I'm writing an Arduino library for the LMP91000 (github), and I'm apparently having some ...
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2answers
42 views

Why there is no high voltage repeater / voltage translator ic (like max232) for I2C

why I2C don't work don't work with long wire, for UART we have 10 volt translators like max232, for I2C why there is no high voltage repeater ic?
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46 views

PIC24 I2C status bits not set

I am working with PIC24FJ192GB106 (64 pin package), and the I2C module is driving me crazy. here is the code: ...
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3answers
63 views

PIC24 - testing I2C module dead/alive

I got PIC24FJ192GB106 (64 pin package) and I cannot get the I2C module working at all. What is the easiest and most straight forward way of testing, whether the module is OK? I am using I2C1 module, ...
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1answer
45 views

EEPROM in beaglebone black

I want to disable EEPROM in beaglebone black by unloading i2c-omap driver. Will it create problem in hardware or any other software support? What should I expect ?
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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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41 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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81 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
73 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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61 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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97 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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128 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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81 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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82 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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43 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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107 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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198 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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77 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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70 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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96 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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81 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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62 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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646 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
121 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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75 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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137 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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112 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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70 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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181 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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69 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
162 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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114 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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366 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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86 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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88 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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287 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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57 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 ...