We’re rewarding the question askers & reputations are being recalculated! Read more.

Questions tagged [i2c]

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.

164 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
5
votes
2answers
2k views

Odroid XU4 and Olimex MOD-IO by I2C via level converter

Long version Like some of you, I do electronics as a hobby and I'm relatively now to this, so I have a few questions regarding the communication between my Odroid XU4 and a nice I2C module from ...
3
votes
0answers
69 views

Increasing system clock frequency on STM32F303 drops I2C clock proportionately - why?

I'm trying to figure out a weird little issue I've discovered while debugging another element of my code. I've got a STM32F303K8 reading and writing to an I2C peripheral. The I2C clock speed is ...
3
votes
0answers
146 views

Strange I2C communication

I am currently trying to test the SHT3x series humidity sensors by Senserion. I have their EK-H4 evaluation kit to get data from the sensors. I can plug in the sesnsors provided with the kit, and all ...
3
votes
0answers
416 views

OLED display using dspic33f i2c

I am trying to use OLED display in a dspic33f microchip. I've successfully initialized and sent data using I2C to OLED. I managed to display a small font(8pt) on the OLED. However, when I tried a ...
2
votes
0answers
67 views

Address Sent bit is not set on STM32F4 Disco

I am trying to interface my STM32F4 Discovery board with a sensor that works over i2c, since the sensor required a specialized i2c protocol, I decided to implement my functions using registers. But ...
2
votes
0answers
181 views

I2C device intermittently fails to ACK

I'm debugging a single I2C master (Raspberry Pi Compute Module) connected to a single slave (a TLV320AIC23B audio codec on separate board) They are connected by 3" jumper wires (4 wires SDA, SCL, PWR,...
2
votes
0answers
2k views

How to properly send stop condition when using DMA with I2C?

I'm using DMA transfer to get 1024 bytes from master (STM32F407VG) to slave OLED screen (SSD1306). The library I'm using does this: ...
2
votes
0answers
107 views

PIC32MX350F256 Errata , IO open Drain Issue

In one of our Product we used Microchip micro controller “ PIC32MX350F256L”. Attached image is small part of circuit showing uC interfacing with a SPI device. We are using bit banging communication ...
2
votes
0answers
3k views

Msp430 I2C Single Byte Read Write

I have this code I've been working on that connects an ITG-3200 gyroscope slave and MSP430G2553 master via I2C bus. It was working fine yesterday but somehow today it is not working. I tried to debug ...
2
votes
0answers
308 views

L3G4200D Gyroscope not sending ACK

I am working on interfacing to a L3G4200D Gyroscope breakout board . I am using it in I2C mode, and the microcontroller I use is the 8051 (via bit banging). I havent connected anything to the SDO ...
2
votes
0answers
2k views

Level shifting with BSS138 - weird values

I need to connect 5V and 3.3V devices via I2C as follows: I've connected 3.3V and 5V pull-ups and tried to measure the voltage. There is 5V on HV and TX_HV but 4,7V on LV / TX_LV. Putting TX to LOW ...
2
votes
1answer
2k views

I2C Raspberry Pi to PIC24F

I'm new to PIC's and PIC programming but I'm working on a little project to try get a PIC24F32KA301 to communicate with a Raspberry Pi using I2C. The Raspberry Pi is the master and the PIC is the ...
1
vote
0answers
52 views

IR Temprature MLX90614 Sensor Diffrent behavior based the I2C Scanner Checking

I need to work with Temperature MLX90614 on Arduino, when i used it's default library code, in bread board sometimes i get correct answer, so i used the soldered circuit for it like this: in this ...
1
vote
0answers
62 views

STM32 I2C Fast Mode Issue

Currently, I am implementing I2C communication with Interrupt. STM32 serves as the slave and Arduino serves the master. MCU: STM32L152RDT6 For previous work, I2C communication in standard mode is ...
1
vote
0answers
24 views

DS90UB948-Q1 internal pattern generator

Does anyone have prior experience with DS90UB948-Q1 FPD-Link III Deserializer deserialiser from Texas Instruments ? I am trying to configure the internal pattern generator block sending I2C commands. ...
1
vote
0answers
67 views

Interfacing touch sensor with stm32f7

I'm having that touch sensor ST IC ST1633i. It's integrated into an LCD. I'm trying to interface with it, but don't know or understand the actual protocol. Here is the protocol So I'm trying to ...
1
vote
0answers
63 views

mcp2221 i2c CLOCK down after ACK

I am trying to control an Analog Devices programming resistor AD5254 by a USB to I2C master device from MicroChip MCP2221. The problem I am facing is that each time MCP2221 is waiting for ACK from ...
1
vote
2answers
50 views

ATmega2560 I2C (TWI) assembler configuration problems

I am using ATmega2560 for testing an I2C code. I wrote subrutines in assembler for init, start, write, read and stop the I2C setup. The goal is that master writes 11110000 to a slave with address ...
1
vote
0answers
60 views

How to properly implement I2C communication between two or more STM32s?

I have a master board with STM32F030R8 and two daughter boards with STM32F030C6. The objective is to communicate parameters between the boards periodically and also on-demand. With some effort I ...
1
vote
0answers
220 views

I2C get stuck on busy with DMA interrupt

I'm trying to interface with NXP device using I2C. I'm initializing it that way ...
1
vote
0answers
40 views

MCP23017 working sporadically

So I've got two MCP23017's on the same I2C bus connected to a RPi. One is addressed 0x20, the other 0x24. The RPi is running my GUI which in turn controls the MCP's which switch 16-way relay boards. ...
1
vote
0answers
59 views

SMBus Read Word Protocol

I want to communicate with a device that is using SMBus. I use PIC18F26K83. I am inexperienced but before that I implemented I2C communication. In I2C communication, what I do in order to write to ...
1
vote
1answer
107 views

Ringing issue on I2C FM+ bus between MCU and few sensors - Power supply issue?

I'm experiencing some issues while probing a problematic I2C bus on the oscilloscope. We want to interface several TLV493D-A1B6, with a STM32L4 (we are working as well on STM32F4 and have the same ...
1
vote
0answers
37 views

What is the maximum supported I2C mode in the FS32K146?

In the S32K146 user-manual guide, it is mentioned as High-Speed mode is not supported by this device. (Page 1481). But in the coming section of the user-manual it is mentioned as device support HS ...
1
vote
1answer
112 views

Communicating with I2C devices using an RTL8710

I've connected an RTL8710 (in "Rtlduino" form) to a MCP23008 (on a breadboard) via I2C as follows: I'm using rustl8710 to program the RTL8710, which works fine and I've already hooked up a display ...
1
vote
0answers
214 views

Honeywell I2C RH Sensor SDA line experiencing fluctuation between Vdd and Vdd/2

I had a problem when implementing I2C communication between NXP Kinetis K50 micro-controller and Honeywell Humidlcon I2C RH sensor. The RH sensor doesn't acknowledge when receiving the default address ...
1
vote
0answers
105 views

I2C stuck on waiting for 8 cycles on DSPIC33ev128

I am new to I2C communication and after reading a number of tutorials on the protocol I attempted to interface a QMC5883L (Chinese Honeywell HMC5883L) to a Microchip DSpic 33ev128gm002 microcontroller ...
1
vote
0answers
129 views

ADXL343 data read

I am using a ADXL343 accelerometer in one of my designs and I am getting strange readings from the device. Just to be sure, I would like to confirm that I am formatting the data properly. (I get the ...
1
vote
1answer
98 views

PIC16 - MSSP Peripheral I2C Master Halting In Middle of Clock Sequence?

I'm using a single PIC16F18857 as an I2C master to talk to five PIC16F1615's on the bus. All is working great, for the most part, however, I've been experiencing a "lock up" where the master is stuck ...
1
vote
0answers
772 views

STM32F103 reading value from lightsensor by I2C

I'm trying to read value from sensor GY-30 BH1750 by I2C but when I check variables in STM Studio, they don't change. Sensor address is 0x23 when addr connected to GND POWER_ON 0x01 RESET 0x07 ...
1
vote
0answers
197 views

interfacing max30100 to 8051(I2C Communication Protocol)

I'm trying to interface heart beat sensor max30100 to 8051 for this purpose I should use i2c protocol. I'm using the following code for that but the sensor doesn't work even though i do the ...
1
vote
1answer
912 views

Two PIC 18f4620 , one as master & the second is slave I2C communication problem

Link for PIC microcontroller 18F4620 datasheet if you may need it I use "Mikroc for PIC pro 6.0" as a compiler and I write a program to communicate between two 18f4620 one is master and the other is ...
1
vote
0answers
190 views

Audio reactive lights - DMX vs I2C

I need to build a system to control lights using line-level audio signal. My idea is to acquire the signal from my mixer using a microcontroller (or FPGA), apply some filters and finally drive 5 leds ...
1
vote
1answer
160 views

Slew rate limiting of bidirectional lines

Assuming the ICs in use don't offer an adjustable slew rate, if I want to limit the slew rate of a unidirectional digital data line, for example of SPI's MOSI-signal, I can put a series resistor at ...
1
vote
0answers
72 views

ADC reliability decreases as inputs connected

I'm using a 4-channel analog to digital converter, the TI ADS1115. I'm reading the values off the i2c bus with a Raspberry Pi. They worked ok for a few weeks- they read reliably about 95% of the ...
1
vote
0answers
321 views

Reuse I2C SCL or SDA Pins to signal interrupt

In an I2C network, I am using an AVR microcontroller (AtMega328p) as a Master and I hooked it up to multiple sensors as Slaves, such as the TMP102, SI1145, MPU9250, among others. All of these sensors ...
1
vote
0answers
144 views

I2C isolated communication error

I'm want to use I2C communication isolated but it's error. I don't know why. My circuit: MCU: STM32F103RDT ISOLATION IC: Si8600 I2C Chanel 0: SENSOR_SCL Chanel 1: SENSOR_SDA Chanel 2: SCL_ISOLATED ...
1
vote
1answer
500 views

MPU9255: Unreliable AK8963 Communications

I'm currently trying to communicate with the InvenSense MPU9255 9-Axis IMU using the FreeIMU software on a Teensy3.2. See comment below for link to FreeIMU code being used (don't have enough ...
1
vote
0answers
150 views

What's happening that my I2C sensor is high on SDA when it might be low, as SCL, when in the time pause between bytes?

I'm using an HDC1080 clone (original by Texas Ins.) temp/humidity sensor which communicates via I2C with an Arduino. Each measurement is 16 bits long and to save its data, you must read first the 8 ...
1
vote
0answers
309 views

I2C lines coupled?

I am using a 5k pullup resistor on my SDA and SCL lines. I am using a 62kHz clock signal on SCL. I have made two boards so far. For the first board I routed all the traces myself, but for the second I ...
1
vote
1answer
498 views

ATmega16u4 and ATmega32u4 i2c bug in Proteus AVR model?

I am trying to use i2c with ATmega16u4/ATmega32u4 in Proteus (version 8.5 SP1) and in my i2c code the following code line hangs the MCU: ...
1
vote
0answers
625 views

Constant values read from LIS3DSH Accelerometer

I'm working with the board STM32F4DISCOVERY from ST microcontrollers. I'm trying to read acceleration on the 3 axes from the accelerometer LIS3DSH via I2C communication. The code is working on one ...
1
vote
0answers
179 views

Wrong I²C signal for some bytes on Atmel microcontroller

In theory I want to start I2C communication as a master with a slave. Then I need to read 5 bytes of data. In practice when I use the ASF provided by ATMEL what it does is start the communication as ...
1
vote
0answers
72 views

Inconsistent values read from PCA9955B error flags

The PCA9955B is a 16-channel LED driver that features programmable PWM and current and has gradation support. It also features open/short detection for all of the 16 channels, which is reported in the ...
1
vote
0answers
570 views

Atmel AVR XMEGA I2C/TWI max speed

I'm planning a communication bus between one ATxmega256A3U and multiple ATxmega64A3s. The challenge is that I need to use as few wires as possible, so I would like to address the slaves without a ...
1
vote
0answers
213 views

New WS2801 LED strip fails while old identical ones are working

I'm trying to add an additional 2 LED strips to my current setup of 4 identical ones. Each strip consists of 32 RGB LEDs with a WS2801 chip run by an arduino which connects to a PC. However I'm ...
1
vote
0answers
233 views

Adding resistor in parallel to digipot

I'm trying to control a device using a digital potentiometer (AD5245S). In my application I can't tie the low-ref of the potentiometer and ground, so I'm using an I2C optical isolator (ISO1541) to ...