Questions tagged [i2c]

Inter-Integrated Circuit (I²C) is a bus for low speed peripherals. Use this tag for questions regarding how to use I²C with an Arduino, or for problems with I²C and your Arduino.

139 questions with no upvoted or accepted answers
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I2C - Confusion

It's not often I ask a question. This one has me a little stumped though. Scenario: I have an 328PB (internal 8mhz), it speaks to a multiplexer on Wire1 (the PB's second IC2 - Minicore lib). The ...
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0answers
96 views

qMenuSystem using DigoleSerial library doesn’t work on my I2C Monochrome OLED

Just like the title says I’m trying to make qMenuSystem to work with my oled display. Here is what I know so far about my display : - It's a Monochrome OLED 128x64 (Blue) Display - It's connecting ...
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0answers
540 views

How to use SPI to set/ read registers for a sensor (Avoiding need for Github Lib)

Ok so as some readers might have seen, my current project involves using MPU's. The idea is sending data via CAN bus to a controlling MCU to then send to a raspberry pi to perform the calculations ...
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0answers
4k views

Why is Wire.onReceive() called during requests?

I'm building a complex I2C-based networking protocol and have noticed that the Wire.onReceive() handler is called both for I2C read and write operations. When the master writes to the slave, it is ...
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0answers
442 views

Connecting arduino and EV3 using I2C

I'm trying to connect arduino uno and ev3 by using this guide (http://www.dexterindustries.com/howto/connecting-ev3-arduino/), everything works perfectly but when i tried to use analogRead block to ...
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0answers
719 views

Raspberry Pi, Teensy and Arduino's on i2c

I just got into an interesting mess. I have 3 Arduino's (Pro Mini's) and 2x Teensy's (3.1's) connected via I2C to a Raspberry Pi Master. The 2x Teensy's I2C data lines are connected via OctoBoards ...
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0answers
121 views

How can I send a number from a master and make the slave read it?

I am building a fan controller using an Arduino and a Raspberry Pi (the Pi is the master and the Arduino is the slave). The Raspberry Pi generates random numbers and I want the slave (Arduino) to be ...
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51 views

Slave unreliably sends bit 7

I'm trying to send a byte from an Arduino Nano I2C slave to a Raspberry Pi 3B Master by directly connecting the two I2C pins of each device with no external pull-ups or level converters. It mostly ...
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58 views

STM32F103 (Blue Pill) with stm32duino + BME280 + SSD1306 strange behavior

I'm going crazy trying to understand some strange reads from BME280 sensor. With this code: #include <SPI.h> #include <Wire.h> #include <Adafruit_GFX.h> #include <...
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130 views

ESP8266 NodeMCU CP2102 ESP-12E I2C with MPU 6050 Error

So the previous two questions could be found here: ESP8266 computtion error and ESP8266 not working with MPU 6050 over wire library and I2C However, it was not resolved, and with updates and debugs,...
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224 views

ESP32: Share I2C bus among multiple freeRTOS tasks - do I have to expect synchronization issues?

I recently inherited some firmware with weird problems in regards to the duration of reading sensor values. The board is based on the ESP32 Wrover MCU and has multiple sensors connected via the I2C ...
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62 views

Can't get MMC3416xPJ to work

I needed a magnetometer with a high Output Data Rate (ODR). This is because I wanted to measure AC magnetic fields of around 20-80 Hz. So I decided to go with the MMC3416xPJ prototyping board which ...
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2answers
2k views

How to connect MPU9250 with NodeMCU using SPI or I2C Slave?

I want to connect 3 MPU9250 sensors, but since there is just one I2C bus, so there are another 2 sensors I want to connect through SPI. Library used - https://github.com/bolderflight/MPU9250/blob/...
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217 views

Is it possible to use I2C and SPI ons the same Clock line?

I'm trying to connect an I2C OLED display and an n RF24L01 WiFi module to an ATTiny85. But I only need 1 extra pin. Is it possible to use the same clock wire/pin for the I2C and SPI device? Maybe with ...
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90 views

STM32F103C8 - Arduino Mega FAST MODE(400000L) I2C communcation not working

I'm trying to connect a stm32F103C8 board (master) to an Arduino Mega (slave) over I2C. I have a master and slave program which runs perfectly fine when the clock frequency for I2C communication is ...
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1answer
1k views

I2C requesting more then one byte

I got an Arduino Uno set up as an I2C master to an ATtiny85 slave, using the Wire (Master) and TinyWireS (Slave) libraries. Communication works good. I have been able to keep the network running ...
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0answers
410 views

How to read the busy flag on LCD?

I have a standard 16x2 LCD screen and I have it hooked up to my Arduino UNO via a I2C backpack (4-bit mode). Since I want to learn about the lcd at a lower level I’ve decided not to use the LCD ...
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0answers
457 views

I2C on ATtiny85 and Si4703 radio

I've got an Si4703 breakout from Sparkfun, which communicates via I2C. I have gotten it to work very easily using a regular 3.3V Arduino Pro Mini, but am now trying to move everything over to an ...
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0answers
386 views

Connection between Arduino Mega 2560 , ESP8266-12F , PCF8574

Another start for achieving something new , I want to connect ESP8266-12F , Arduino Mega 2560 Board And the PCF8574 I/O Expander (I can use MCP23017 also) together , Where ESP8266-12F will take ...
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1k views

How to prevent Wire.requestFrom from hanging?

I'm trying to read data from an Arduino Uno I2C slave via Wire.requestFrom() on an Arduino Uno master. The slave's onRequest handler is simply: void I2C_Send() { byte myArray[4]; myArray[0] = ...
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41 views

Why am I only receiving the first address byte? (I2C Protocol)

Expecting the slave to ACKnowledge and return data, but it does not. This is my protocol. This is my Datasheet. Also FYI I'm on an Arduino Fio but I am not inheriting the Arduino library. #include &...
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263 views

Adafruit Trinket 3v with LED matrix backpack producing error

I have been wanting to create a Arduino watch. I built the circuit with an Adafruit Trinket 3v and an Adafruit LED matrix backpack (8*8). When I try to upload this example code: /*********************...
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141 views

Reprogramming a specific slave from the master ATTiny 85 (connected to IDE)?

Given that every ATTiny connected already has a bootloader (micronucleus) installed, here's my theoretical chain: Computer > Master ATTiny (Connected via USB) > ATTiny Slave A > ATTiny Slave B Is it ...
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183 views

Too many Bytes Using Ultrasonic Sensors

I need to send one transmission and record multiple distances with 4 receivers, but everytime I use more than 2 receivers, the serial data does not print. What can I do? P.S. I'm using 5 SRF-02 ...
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594 views

ATtiny85 + HC-05 + Oled = smart watch

I am using an ATtiny85 for making a smart watch. Bluetooth module HC-05 with ATtiny85 pins PB3->TX, PB4->RX and it works. Secondly I have connected a 0.96" OLED on PB0 (SDA) and PB2 (SCL) and this is ...
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0answers
661 views

I2C — set int pin

I am using a blend micro board, where the digital pins 4, 6 and 7 are reserved. I have connected a MPU6050 which uses the I2C protocol, so there is the need for the i2cdev lib to handle that. The ...
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103 views

Teensy and MS5803 sensor

I'm trying to use the MS5803 pressure sensor with a Teensy 3.2. Compiling the Sparkfun, or other, libraries, however, results in no output. Can you provide guidance on how to modify the libraries to ...
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0answers
126 views

Basic communication between Cotek and Arduino UNO

I am trying to get a reading from my Cotek through my Arduino and have it display on an LCD screen. When I run the code, though, nothing shows up. I am EXTREMELY new to using pretty much all this ...
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139 views

I2C with an arduino, a PI and an IO expander

im working on a project which requires alo i/o pins. For that reason i bought a pcf8574P 8bit I/O expander which uses the I2C protocol. The problem is how to combine the Rasp PI and the arduino. For ...
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334 views

Receiving multiple bytes from an RPi using the i2c protocol

Trying to send bytes from an RPi as a master to an Arduino as a slave. The send uses the write_byte(addr, value) function and seems to be working perfectly. The Arduino however has issues with ...
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0answers
1k views

Unexpected Timer Conflicts (Uno)

I've been working on a project (Arduino Uno: Atmega328) that implements a gyroscope (which is used with the LSM9DS0 spark-fun library) that is communicated with through I2C and uses a Servo library. ...
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0answers
1k views

How do I use I2C from an Arduino Uno when I have a GSM shield mounted?

This may be an extremely obvious question but I don't seem able to find a definitive answer. I have an Arduino Uno and a Sim900 GPRS/GSM shield fitted on top of it. I had I2C working on the Arduino ...
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176 views

i2C and lost connections with IO errors

Having issues troubleshooting IO errors using i2C . Running a Python script on a raspberry Pi as master talking to an Arduino slave. The problem is that when making any change in my code that results ...
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0answers
205 views

GPS - Speed doesn't update as should - EM408 & Arduino Mega & GSM

I'm developing a system that will get the GPS signal and send it though the GSM with information about position, speed and temperature from some digital sensors. Currently I'm using the GPS EM408, ...
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1answer
752 views

Getting inverse values of acceleration and tilt for the MPU 6050

I'm using the I2C library to connect to a GY-521 board and, when executing the getAcceleration() methods I get gyro values and viceversa.. This is my setup (I'm using a proto shield but that shouldn'...
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1answer
709 views

Arduino Pro Mini I2C Problem

I am trying to connect a distance sensor VL6180x to Arduino Pro Mini via I2C. Yesterday it was working without any problems, but today it refuses to work, even though I haven't changed anything. The ...
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22 views

OLED display on I2C causes esp8266 to reset

I have connected two temp sensors and an OLED display to a NodeMCU using I2C. When the program reaches the instruction to print the measurements on the display the program crashes and NodeMCU resets ...
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35 views

Multiple sensors I2C stop working suddenly

I am using multiple temperature sensors using I2C. Some of the sensors are connected via TCA9548 multiplexer. When I run the sketch it runs fine for a few minutes but then it suddenly stops working ...
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35 views

error at compiling : 'class TwoWire' has no member named 'setClock'

I am a newbie C programmer and I just started with Arduino web editor (Win10-Firefox)to code for a Raspberry Pi (3B) board. RPi is on line via ethernet connection. I tried to compile an example from ...
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1answer
26 views

What is “tws_delay” and how can I use it? (with an ATTiny85)

EDIT: Alright I'm stupid, I had the 2012 library installed somehow, maybe when I downloaded it indirectly from another old tutorial site. Thanks a ton to Peter Freerick for pointing that out! It ...
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34 views

2xArduinos, 2xDevices, I2C setup

Is it valid configuration using hardware I2C pins: Especially: can NanoEvery initialize communication with DS2482, while it is slave for Mega2560? Using Wire library or should I use software I2C when ...
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25 views

I2C LCD displaying gibberish

I have connected a I2C LCD with my NodeMCU v3. My pin configuration is as follows: Node MCU ---> I2C LCD GND GND 3V VIN SDA D2 SCL D1 I have been testing a ...
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23 views

Different Counter Reading on Serial Monitor Vs .96" OLED I2C

I've cobbled some code together from reading multiple sources on the web. Makeatronics in particular to help me get this rotary encoder code together (shout out to them). I'm pretty close to the end,...
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33 views

leonardo mouse readings

hi there im using arduino uno + usb host shield and i have taken the readings from the usb mouse in this line of code : x = mi->dX; and the x output is the speed of the mouse x coordinates and i ...
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33 views

Connecting OV2640 with 17 Pins Binocular Camera module, to any microcontroller (System clock on module pin 18 -NC)

These pins are on the module: 3.3V GND VSYNC SCL SDA HREF D0-D7 DCLK PWDN I have tried many codes and connections of the OV7670 Monocular cameras, none seem to work(Instructables , Circuit Digest , ...
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41 views

I2C master's output is always 255

we are using 2 Arduino UNO as a master/slave for this i2c protocol. we used the first Arduino(slave) as a sensor that will input dummy data (in this case, temperature data). the Arduino(master) should ...
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21 views

Does DFR0063 I2C LCD work with Arduino Due? I cannot even pass i2C scanner

I have 2 Due and Two DFR0063 I2C LCD. I cannot even pass i2C scanner. I always got No I2C devices found. I tried both SCL/SDA and SCL1/SDA1. For SCL1/SDA1, I do add 10K pull up resister. But still ...
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1answer
34 views

HTU21 on GY-21 breakout board I2C problem

I am interfacing the HTU21D sensor with my nodeMCU v3. All good! I managed to get some readings etc. But when I re-upload my code the device does not respond. If I remove the power supply from the pin ...
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34 views

eps32 bad adc even with external adc (ADS1115)

Im trying to read an analog value with my esp32 and send it over wifi to another esp32. The wifi part works flawless, however when i try to read an analog value form the esp32 its not useable. It ...
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38 views

Configuring the registers of i2c AD converter ADS122C04

I am not able to set the configuration registers of the TI´s converter chip ADS122C04 using arduino MEGA via I2C. The code mainly consists of the following: 1-reset the chip (one byte) 2-choose ...