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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PIC16F1509 I2C problem (XC8)

I've got a problem with my PIC16F1509 code. The PIC is running in slave mode for the I2C. With the code below I'm able to write to the device and change the position and run this all day long but ...
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38 views

ADC speed for precision medical instrument

I am studying a bio-medical instrument where glucose in blood is measured using light reflection principle as shown: Below equation is used to determine glucose level: LED is blinked at fast rate ...
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I2C Bus is Not Responsive When Engine Is Running. How to Diagnose and Fix?

I've got a solder-less bread-boarded prototype microcontroller with a few I2C devices that take some measurements on a motorcycle. For now, The MCU is powered by a LM7805 with decoupling caps near the ...
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125 views

Reasons why an I2C bus requires a minimum value of capacitance on the clock to function?

I have a microcontroller (LPC1768FBD100) and am using I2C to configure a 3 port eithernet switch (KSZ8863RLLI). I’ve made about 100 boards so far and they have all worked well, except one. For some ...
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126 views

I2C dummy write

If you want to read from the I2C bus you have to: Send start condition Send 7 bit slave address with R/W being a '0' which indicates a write Send register number where you want to read from ...
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41 views

Error communication in I2C in PIC32 [duplicate]

Duplicate question was also asked by me and the current question has different code I have a PIC32 starter kit and I am making ...
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3answers
76 views

Error interfacing DS1307 RTC with PIC32

I am interfacing DS1307 RTC with PIC32MX795F512L. I am using I2C1 for ...
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45 views

Intel Edison and I2C OLED

I recently bought a Micro OLED Breakout (https://www.sparkfun.com/products/13003). I cannot seem to communicate with the OLED using an Intel Edison with I2C block; calling "i2cdetect -y -r 1" does not ...
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58 views

OPT3001 conversion formula / equation?

I am struggling to find a real conversion formula for converting the RAW value into result that makes sense. I am using an OPT3001 sensor from TI and ATTiny25 as MUC. I have found one example online, ...
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29 views

How to estimate a value for IC capacitance in a I2C bus?

What is a reasonable value to use as the capacitance a I2C device adds to a bus if so is not stated in the datasheet? With this value I intend on calculating the pull-up resistors to eventually use ...
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1answer
24 views

mcp23008 problem

i am using mcp23008 that is a i/o expander ,everything is OK but in datasheet there is a capacitor and i don't know what is that doing ,also i didn't see it in any designed board that i found in ...
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74 views

Understanding Source Code of I2C communication

So in my University studies we recieved few source code samples that are working with a OPT3001 Light Sensor. Our studies do not focus on engineering tasks in general, but this is a lecture that ...
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86 views

STM8 multi-byte I2C reads

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beaglebone black i2c - eeprom not detected

In my BBB (arch linux) I cannot find eeprom, it used to be in i2c-1 but for some reason (maybe kernel upgrade to 4.1.4) is not ...
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1answer
71 views

I2C PCB Layout Considerations

I wanted to ask, what general layout guidelines and/or routing concerns exist for I2C in a PCB design? Edit - Consider a 31mil thick, 4Layer PCB with stack up: L1 = signal - 0.5oz + 1oz plating L2 ...
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3answers
97 views

I2C: Unable to Read Multiple Byte using Bit-Banging method

I am using Bit-Banging for I2C communication via PIC24FJ128GA010. The code works fine for writing 16bytes to EEPROM ( I recieved ACK = 0 for every Byte write ). While reading EEPROM I am able to ...
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77 views

Slave can't drive I2C bus low

I'm trying to use an I2C isolator IC (ADuM1251) to isolate one of the slaves on my I2C bus. Without the isolator, the communication works fine. With the isolator, my setup is the following: I'm ...
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1answer
37 views

TWINT flag never goes up

I want to establish I2C connection between two atmega2560. First one is working as a master, and second as slave. Master works on a transmitter mode, and Slave works as receiver. On Master side: ...
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2answers
292 views

Make Arduino and 89C52 talk to each other

I am trying to create a project in which I am required to make Arduino and Atmel 89C52 talk to each other. I know this can be achieved via UART but the problem is my Arduino is already using its ...
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73 views

U(S)ART/SPI/I2C - any common/prevalent/recommended connectors?

Good morning everyone! I'm currently building the board with the STM32F417 microcontroller, and I want to have separate (out-of-GPIO) I2C, SPI, UART and USART outputs on the board. But I'm lost on ...
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1answer
69 views

Communicate with 3 Sensors with the same I2C address

I got three sensors stick from sparkfun : https://www.sparkfun.com/products/10724 which each one got an arduino pro mini that filters the data before to send to a main Arduino. Like this: and ...
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1answer
71 views

PIC32 and I2C EEPROM interface problems

I am writing code for a PIC32MX250F128B to interface with the Microchip 24LC02B EEPROM with I2C interface. I have followed the datasheet of the EEPROM, the PIC32 and section 24 of the PIC32 family ...
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55 views

Waveform decoding

I am trying to get the information from my mouse's optical sensor, strictly ΔX and ΔY. I looked up the datasheet for the microcontroller that communicates with the optical sensor and all I could find ...
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401 views

How many i2c slaves can a i2c master support?

Is there a maximum number of i2c slaves that a i2c master can drive? What are the physical limiting factors?
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2answers
70 views

Why does the I2C interface use the open-collector/open-drain?

The open-collector adds inconveniences like requiring an external pull-up resistor and slows down the throughput. Why did the I2C designers choose to use open-collector/open-drain?
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3answers
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Why are pull-up resistors required to be connected to the 2 lines of I2C? [duplicate]

Without pull-up resistors connected to the 2 lines of I2C, I2C communication fails. Why is there a need to have pull-up resistors for I2C? In contrast, UART and SPI do not need pull-up resistors. ...
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2answers
78 views

Not getting correct values in I2C interfacing in Atmega

I'm very new to the concept of I2C and I've been having some problems interfacing I2C between 2 Atmega32(s). I have one Atmega32 as a Master to which an LCD screen is connected and another I2C as a ...
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143 views

Arduino interface with I2C Pressure Sensor

I have a Honeywell ASDXRRX100PD2A5 I2C Pressure Sensor that I want to read using an Arduino. Looking at the datasheet, I know that the I2C address is 0x28, and I have had a play with bits of code ...
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45 views

Pic24F: #define I/O pins?

I am trying to #define Pic24f I/O Pins with user defined Name. here is the part of my code : ...
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1answer
104 views

PIC24f: How to Generate Start condition using SPI for I2C device?

I am trying to communicate with the device having internal communication as I2C while externally it has two different pin for Input & Output along with a separate pin for Clock. Here is the link. ...
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55 views

Shift registers, flip-flop, Multiplexer & Demultiplexer with microcontrollers utility

While i read alot about the popular 74HC595 shift register and its use for multiplexing i can't find anything about the following chips: MC14053B Triple 2−Channel Analog Multiplexer/Demultiplexer ...
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2answers
57 views

Use GPIO for switchable Pullups of I2C

I'm designing a general purpose interface board and want to make available as many of the peripherals available and usable on an expansion header without the need for permanent (soldering) changes. ...
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29 views

does CompactRIO modules have builtin pull-up/down resistors

I have Compact RIO 9076 with 4 different modules: ni-9205 (Analog Input), ni-9264(Analog Output), ni-9402 (Bidirectional Digital I/O), ni-9403 (Bidirectional Digital I/O). I have several 3rd party ...
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54 views

I2C - addressing

In the i2c protocol, I would like to know how the slave & master address are assigned. Most of the internet doc talk about how the protocol work, but i wasn't able to find doc about i2c slave ...
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45 views

Which bus is it necessary to use and where can I find it?

I'm trying to make a tiny navigation system with 6 IMU sensors. The main requirment is accuracy and distance between sensor and master. Now in prototype I use I2C, but the length of wire connecting ...
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73 views

Why does I2C look like this?

I'm trying to debug an I2C device, and the wave is looking really weird. Why is it curved?
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70 views

I2C -internal and external pull up

I have a doubt in I2C pull up resistor. Actually I am developing a I2C module using GPIO pins. I have used external pull up resistor(10k) for the SDA and SCL lines. Do I need to enable the internal ...
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65 views

I2C read operation doubts

I am trying to read the 16-bit data from a location in EEPROM using I2C bit banging. Viewing the oscilloscope, the write operation seems to be correct. However, the read operation does not seem to be ...
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77 views

I2C on atmega168/328 using interrupts

I have the following I2C configuration with an ATmega168 (1 MHz) as the master and an Arduino Uno (16 MHz) as the slave. The command for the LED connected to the slave comes from the master and ...
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47 views

How do i turn multiple usb ports off based on multiple sensors

I'm looking for a way to turn a usb port on an off from an Arduino, I'm looking at purchasing something like this and somehow using a pressure or light sensor to turn the usb port on and off. I was ...
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151 views

Using GPIO pins as software I2C pins and finding analog value of those pins

I am using AT32UC3C microcontroller which has 64 pins. I am using gpio pin PB01 as SCK and gpio pin PA04 as SDA and ticking then manually high and low. These pins are configured as GPIO_OPEN_DRAIN and ...
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31 views

I2C Display Module (NHD-C160100-DiZ) for DIY Scientific Calculator Help

Good evening everybody reading, This is a project I've been developing for about 6 months. I am stuck because I can't get the display module (datasheet here) to work. I attached my schematic for the ...
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3answers
219 views

Using I2C and SPI communication on the same same clock and data lines

I am using a PIC18F25K80 with multiple slave devices. All of them uses I2C except one. What i want to know is that can i first use I2C with the devives that uses I2C and then close I2C, change clock ...
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2answers
42 views

How to program via ICSP when chip is in-circuit with interfering chips?

My Circuit is: USBTinyISP <-usi/icsp-> ATTiny85 <-usi/i2c-> MCP4725. That is, the USI pins used to program the t85 are also used for i2c in the final circuit. When I try to flash-program the ...
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1answer
94 views

I2C-to-SPI bridge and SD card

I am using a PIC18F25k80 microprocessor, which is communicating by using I2C protocol with peripheral ICs. After collecting the data from the ICs I want to store them in an SD card. However for the SD ...
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2answers
107 views

How to correctly wire an interrupt pin, clock pin, PWM pin, SPI pin

I've a question about how to correctly wire some microcontrollers pins. In particular: Interrupt pin on microcontroller (pull up/pull down resistor and with which value) Output clock pin from a ...
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66 views

I2C programming ATTiny88

I am beginner at programming uC's. I have read all the tutorials on what is I2C and how it works, but I couldnt find any help specific on how to create a connection between my sensor and ATTiny88 ...
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69 views

Running Bus at Low Speed- I2C bit banging

I am implementing I2C using Bit bang. The slave can accept maximum baud rate of 400kbps. Iam not using external pull up, which is required because of which the fall/rise are not accordingly. I read ...
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120 views

Arduino UNO + PCF8574P + 4pcs HC-SR04

I'm trying to connect 4 ultrasonic sensors HC-SR04 to Arduino UNO using a NXP's PCF8574P chip. If 4 sensors are connected to Arduino pins, everything's fine. The problem appears when I try co bind ...
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2k views

Why is serial EEPROM preferred over parallel EEPROM?

In the wikipedia page for EEPROM: http://en.wikipedia.org/wiki/EEPROM it is given that "Parallel EEPROM devices typically have an 8-bit data bus and an address bus wide enough to cover the complete ...