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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I2C Module Not Responding

I am writing a basic I2C slave as part of my code on a 20-pin 8-bit PIC16f MCU. As best as I can tell, this microcontroller has a module that watches the I2C bus and only updates my registers if there ...
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LSM303DLHC outputs frozen

I've was trying all afternoon yesterday to get some data out of my LSM303DLHC using an STM32L152 Nucleo board. Finally I got all the I2C stuff down, managed to set some registers, verify their ...
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28 views

Getting gyro values from MPU-6050

I have an MPU-6050. I have known that it uses I2C bus for communication, but I have no experience of the I2C bus. I know that SDA and SCL serial wires are used in this communication. I have got ...
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How come the decoder gives a question mark?

I'm using a scope to debug I2C (bit banging) by letting it capture the signal. I think that the output should be good, but the scope's decoder gives the following: where there is a question mark ...
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Does each I2C START signal need to be closed by a STOP signal?

Could two I2C START signals be sent one after another without a STOP signal sent in between? Below is an example of bit banging, where there is not STOP between the first and second START: ...
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Why does the clock stay at high?

I'm very new and I'm trying to do an I2C trace of ADXL345 with Ch1 to SCL and Ch2 to SDA, but the traces look like these: Is the clock not supposed to oscillate continuously? Is it normal for it ...
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27 views

arduino I2C maximum number of writes per Transmisson [migrated]

Is there any limit on the number of Wire.write() commands consecutively in between the Wire.beginTransmission() command and the Wire.endTransmission() command for the Arduino Wire library?
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15 views

Systick Timer problem

I am trying to use the systick timer to update a variable which stores millisecond elapsed on a STM32F051 in Coocox ide 1.7.8 . I also want I2C and UART communication in my project. I managed to get ...
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67 views

Why is my SSD1306 OLED only displaying half of the screen area?

I am trying to get this display working with my arduino via i2c: http://www.buydisplay.com/default/0-49-inch-oled-display-module-64x32-pixel-ssd1306-i2c-white-on-black I have successfully initialized ...
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19 views

ad5359 address not shown

I am working AD5259 , its a digital potentiometer. Its connected to i2c bus on raspberry pi. But the address of device is not shown. Datasheets says its 0X18. I guess the device does not respond to ...
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47 views

Xmega128C3 TWI read error

I'm interfaceing an Xmega128C3 with MMA8451Q acceleration sensor via i2c. I was able to initialize the accelerometer, I checked every transmission on oscilloscope, it was done properly. The problem ...
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39 views

PIC18: I2C with external triggered interrupt stuck in ISR

I am trying to implement a simple, external, pushbutton trigerred I2C communication between a PIC18F46K22 and a ST LSM330D MEMS sensor. I tried to find straightforward libraries for the easy ...
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38 views

Protecting I2C bus with diodes

I'm trying to add some protection to an I2C bus, and keep getting an unexpected result. simulate this circuit – Schematic created using CircuitLab In principle, I'd expect this to clamp ...
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36 views

reading temperature from ds1621 using stm32f4 discovery

I am trying to use the stm32f4 board to read temperature from a ds1621.As mentionned in the data sheet ,it uses i2c protocol. I implememented this code based on what i found on the net. My problem is ...
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224 views

Does the STOP condition have any meaning on a single master I2C system?

I'm currently working on rewriting some of the code on my I2C driver, and I'm trying to figure out the exact purpose of the STOP condition. I believe that on a multi-master system, once a START ...
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3answers
96 views

I2C and SPI on the same bus

I have already configured an I2C protocol between a master device (PIC) and two slave devices (sensor ICs). After obtaining the measurements from the sensors I want to store them on an SD card. For ...
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Why does I²C only have pull-up resistors (interview question)?

The interviewer wanted to know why pull-up resistors are used on SDA and SCL when the opposite logic can also be implemented. Is there an explanation for why pull-up resistor usage is the chosen ...
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59 views

I2C SoC explicitly not multimaster

While reading the guide of a chip I'm about to take in use (Intel Edison), I noticed the SoC is specifically not supporting multi-master. The SoC is always I2C master, it does not support ...
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Arduino LCD 2x16 and PCF8574AP works well for limited time [migrated]

I have got a problem with operating my typical 2x16 LCD with PCF8574AP. I have read the entire internet about that, other topics etc. but none of them can relate to my problem. The thing is that my ...
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65 views

High pass filter for I2C

I am building a gimbal and passing I2C through sliprings. Right now I have 1.6Vpp spikes at about ~32kHz on the i2c bus. (The spikes are harmonics from motors which are driven at 16~17kHz). The i2c ...
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45 views

toggling a pin using the hardware compare feature of timer1 AVR

This link - says: "In CTC mode, you can also trigger interrupts, but it is also possible to not use interrupts and still toggle an output pin. Using it this way, the functionality occurs ...
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76 views

I2C: How to connect Raspberry Pi (power cut) to ATmega328p

I would like to interface a Raspberry Pi with an ATmega328p microcontroller using the I2C bus. These two parts act both as masters, but not at the same time. The Raspberry Pi is powered through the ...
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2answers
68 views

What are the address input pins used for in ds1621?

I just bought a ds1621 temperature sensor and started reading its datasheet. I found out that it have 3 pins (A0,A1,A2) which as specified in the datasheet are chip address input. Can somebody ...
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50 views

Measure I2C bus capacitance

We are trying to calculate how many I2C slaves we can hook up the I2C bus. We tried to run a square wave through a serial resistor and measure the rise time but we get a strange result. More nodes ...
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13 views

NVT I2C bus capacitance

I would like to use NXP NVT20XX as bidirectional voltage-level translator in my system (I2C at 100kHz, 6 slaves) and I only don't understand one thing. I am little bit confused. In the datasheet they ...
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99 views

Connect large number of MPU 6050 I2C devices

I am quite new to electronics , in my project I am trying to connect large number of MPU6050s(about 10 sensors) I2C devices and try to get the reading 'simultaneously'. Some questions that I am not ...
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64 views

how to communicate between 3 devices

i want to communicate between uno, mega and netduino, which protocol should i use i want the uno and mega to send information to the netduino which mean that i don't need duplex connection which mean ...
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1answer
66 views

Fixing a noisy I2C bus

I'm trying to get an I2C bus working but there's a ton of noise and I don't really know what's causing it. The circuit is pretty simple, an ITG-3200 and an Arduino DUE. Here is the problem: As you ...
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78 views

I2C hanging after 2 minutes

Background Information I am designing a small PCB for 4* I2C devices, the baud rate of the I2C is not a major issue so 100kHz was the target. The I2C devices are a RTC, LM75, 24AA04 and a MSP23017 ...
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24 views

I2C slope control for falling edges

I2C has this requirement in the spec for slope control on the falling edge @ 400Khz. It appears it's to make it so it doesn't fall too fast. I read somewhere else this was done for EMI purposes, ...
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76 views

Problem with I2C on PIC18F25K80

I am trying to configure an I2C protocol between a PIC18F25k80 and a barometric pressure sensor (the link for the datasheet is provided below). I can't figure out what the problem is. Initially it ...
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36 views

Will a I2C switch boost the overall bitrate?

I am currently working with a wired I2C bus system consisting of 6 individual bus lines with 4 slaves on each. They are currently all connected to one I2C bus and for each slave i add the bus becomes ...
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65 views

rasperry pi with i2c arduino leonardo

I'd like to connect a Raspberry Pi A+ with an Arduino leonardo. I'd like the rapsi to be able to upload HID sketches on the arduino.Then I'd like the arduino to run the sketch over the USB interface ...
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61 views

How many bytes can be sent in a single i2c message?

I've been working with i2c lately between a beaglebone and an Atmel 328P where the Atmel controls a number of devices under the direction of the beaglebone. In order to accomplish what I've done so ...
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Relation Between 8:1 Mux Signal , Mux Accessing Time & output of Mux

I have asked a question yesterday . Now i have a strange issue. I am working with Beaglebone white in Android platform . I have one external ADC (ADC121C021CIMM - connected through 8:1 Multiplexer ...
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115 views

MPU6050 DMP values read

I am using MPU6050 breakout board IMU along with ATtiny2313 microcontroller to get the accelerometer and gyroscope values from the IMU. Here's the question : I want to know what values are computer ...
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1answer
147 views

Relation between ADC register value & ADC accessing time?

I don't have any Electronics background.I am Software Engineer. I want to know that is there any relation between accessing the ADC buffers with a time (T ) & the ADC buffer values. I am working ...
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211 views

Interfacing 2 accelerometers through I2C

I am looking at designing a system where 2 accelerometers are connected to a microcontroller using I2C however I am unsure as to how this would actually work. In particular would I need a ...
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1answer
176 views

Raise input for a voltage monitor IC

I was looking over LTC2990, which is a voltage, current and temperature monitor. It is perfect for my project as I'm newbie. I want to build a power supply which will show on a display the voltage, ...
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1answer
73 views

Controlling an ESC for Brushless Motors with an RPi

Originally posted on Robotics, but guess it's not active enough. I'm looking to build a new (first) quadcopter without the conventional flight controller and radio, with an onboard RPi and applying ...
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1answer
224 views

STM32F3 Discovery reading values from sensor using I2C

I need to read values from on-board LSM303DLHC (connected via I2C) sensor and send them through UART. UART part is working but PuTTy shows: "S▒▒" every restart... Can anyone tell me what's wrong? I ...
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59 views

Microchip PIC18F24K50 I2C master talking to SHT21

I'm building a library to talk to an SHT21 Temperature/Humidity sensor using the XC8 I2C libraries. I have the following functions: ...
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I2C Slave on ATtiny841

I am using an ATtiny841 microcontroller as an I2C slave, but I have difficulty finding information on it. So for, all I have are application notes and reference code for TWI and USI module. It seems ...
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2answers
52 views

Using internal pull-ups for TWI on AT32UC3B?

Does anyone know if it's possible to use the built-in pull-ups for TWI on the at32uc3b chips? I've been adding external pull-ups to my TWI circuits in the past because I couldn't find any concrete ...
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1answer
109 views

problem of transmitting data from serial device to bluetooth on Arduino

I am using an accelerometer which uses serial communication on Arduino (UART), I wish to transmit the data to a bluetooth module (blusmirf gold) using I2C and finally read it from my android ...
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4answers
503 views

Do all I2C devices have separate read and write addresses?

I'm using a particular I2C device, and when it is connected, I need to write data to it by sending data to address 0x30 but then to read from it I need to read from address 0x31 (or by doing 0x30 | ...
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82 views

FT232H read ACBUS9

First time on this board so you will excuse me if the question has been answered before ... Right down to the nitty-gritty I have a board based on an FT232H chip, AD bus is used in I2c to ...
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81 views

Slave I2C timing relative to master clock edges

I am working with the STM32F4 microcontrollers. The I2C peripheral uses a clock setting. I have been told that it does not matter when the peripheral is used as the slave device. If that is true ...
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26 views

Turn on/off serial and I2C display [duplicate]

I have 2 character display, one is controlled by serial another is controlled by I2C. I could control both with serial or I2C alone. But that's not the point. Now what I want is, to completely turn ...
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3answers
83 views

ADC with I2C interface with multiple addresses

I want to connect 31 ADC slaves to a master. The ADCs simply should measure voltage and response its values to the master after request. I thought about using I2C as bus system. The problem is that ...