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.

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I2C and SPI which interface to use when?

I have seen I2C and SPI interfaces being used with EEPROMs and other ICs. From an Hardware Perspective, what interface should be selected when ? One obvious reason I can find is that, I2C uses only 2 ...
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70 views

Why the MAX14830 does not transmit?

I am using a MAX14830 as an I2C-UART bridge. My problem is that it does not trans it after I write data to the transmit (THR) register. My initialization procedure is as follows: Reset the chip (set ...
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39 views

ADS1115 I2C won't communicate with CPLD

I have an EPM240T100C5, which is a 240 LE CPLD with a 50MHz internal clock. And as part of a project, I need an ADC, which means that I cannot use too much logic elements, thus, I create a simple ...
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74 views

(beginner) I2C slave protocol : basic in bit transmission [closed]

I am studying I2C protocol and have some doubts: I2C and SPI are communication protocols. They work same but I2C has not chip select as SPI. I2C has ...
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1answer
64 views

Multiple PCIe devices in a single M.2 slot

I have a M.2 M-keyed slot on my laptop, and multiple M.2 PCI-e devices that I'd like to use at the same time. I've been looking for a M.2 switch or splitter of sorts but couldn't find anything, so I ...
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I2C buffers connection

While connecting two I2C buffers, we can't connect their SVOs together. They should always be at the far end. Can u tell me what difference does different SVO makes so that we get a different output. ...
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1answer
49 views

Can we use 2 pull-up resistors with same voltage on the I2C lines?

I have one EVK board with I2C lines which are pulled up to 1.8V. On the other board again this I2C lines are pulled up to 1.8V and then level translated to 3.3V. I think the other board I2C lines need ...
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79 views

I2C gets Interference from motors in an Arduino project

I built a small Arduino "robot" on a tracked chassis. The device uses MPU-5060 for direction finding (on a prototype shield) and Adafruit MotorShield v2 to control two 320-type motors. The ...
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52 views

Bit-bang I2C implement on DS1307 and Atmega328P problem

I currently implement I2C bit-bang for Master Arduino (AVR) to Read/Write to Arduino Slave using Wire.h and DS1307 RTC. My bit-bang i2c work perfectly with Arduino Slave read 8 bytes without ...
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1answer
48 views

Missing 1 bit shift Bitbang I2C Atmega328p

I implement bit-banging I2C on Atmega328P and met the problem when the Master receives data from the slave. I'm in depression in debugging this code since I found no problem. Master Write work ...
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220 views

The Differential I2C Bus Extender is only working for 1 channel

Edit: More information about this question can also be found here: https://forum.sparkfun.com/viewtopic.php?f=105&t=55786 Currently I'm working on a project where I want to use multiple scales in ...
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PIC18F25K50, ADS1114 and I2C

I have a minor problem here. I am programming a board with PIC18F25K50 on which I also have three ADCs (ADS1114 from Texas Instruments) for three loadcells. It is a HID device, I have the USB part ...
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111 views

What does clock/signal speed actually do?

This is may be a silly questions but I am curious. I know that in circuits power lines are at speed near light but why are signal lines so different? Let's say I use I2C(MCP23017) I can choose between ...
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83 views

Decreasing I2C SDA SCL interference

I am setting up a fast I2C communication between a microcontroller (STM32, master) and an FPGA (Zynq-7000, slave). Currently, it won't work correctly because whenever the FPGA pulls down SDA, it ...
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1answer
110 views

Microcontroller IO pin configuration I2C

I'm using this Microcontroller S32K142 64 pin. In the reference manual, I can see a lot of pins which I assume to be Output only are mentioned as Input / Output. For example, the Microcontroller is ...
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1answer
48 views

How to evaluate the Logic Compatibility with I2C lines

I have a microcontroller connected to another I2C device. I'd like to evaluate the I2C Logic Compatibility between the devices. But since the I2C is an open-drain protocol, the resistors are outside ...
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465 views

I2C communication not working

I am trying to read data from / write data to a Xilinx Zedboard (FPGA platform) using an external microcontroller via the I2C bus. The schematic for this would currently look as follows: As you can ...
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34 views

Changing the i2c address of a different type of OLED display

I am working with 2 oled displays, both which uses the ssd1306 chip which has interchangeable addresses. Now, there's one chip that looks like this : This chip has a clear indicator on what to ...
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1answer
62 views

I2C Level translator 5 V to 1.8 V using MOSFET, output look weird

I am designing an I2C level translator using MOSFET. I am using BSS138 DATA SHEET. My clock can go up to 1 MHz. The output is not coming properly for fast mode plus (CLK = 1 MHz, RISE TIME = FALL TIME ...
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1answer
83 views

What's wrong with this cable?

I have a circuit with an RTC (DS1307) and an LCD display, both connected to an I2C bus. Because the RTC requires a 5V level (the RTC breakout I use has built-in pullups) I also use a level shifter. ...
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RV-3028-C7 stuck in POR EEPROM refresh

I just purchased an RV-3028-C7 RTC module and tried to get it working. I2C seems to work, so I can read some registers: ...
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1answer
103 views

Slave protection from master in I2C

I am trying to answer this question: How can an I2C slave protect itself from being overwhelmed by an I2C master? I think the answer is this: As what I know is for each transmitted bit, the master ...
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1answer
53 views

I2C: Do I still need pull-up resistors if I use a logic level converter? I

Electronics newbie here. I have the following setup - three Arduino Nanos, a BME280 sensor, an MPU6050 gyroscope, a GPS GT-U7 (Goovvv Tech) module and an 128x64 (1.3in) OLED display. All except the ...
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Getting the MLX90615 IR Temperature Sensor to work with PIC32 Harmony-Generated Code

I am working to get the MLX90615 sensor from Melexis working through I2C on a PIC32 MCU (MX32440F256H). I am using Harmony's generated I2C1 functions to accomplish this and have been referring to the ...
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How to read values from registers in AS7262 spectral sensor with I2C using STM32H743ZI (STM32CubeIDE)

I have been trying to read data from AS7262 Spectral Sensor using STM32H743ZI2. I am writing the program using HAL Library. Here is the code that I tried for accessing the registers of the sensor, ...
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2answers
68 views

On initiating I²C communication, status register SR1 gets reset immediatelly

With the following code to handshake an EEPROM ...
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1answer
96 views

I2C slave device address bouncing around [closed]

I am interfacing an SHT20 with a Raspberry Pi via I2C. In Linux, I am using i2cdetect from the i2c-tools package. The issue is that I'm expecting to see a static address in this table, but instead I ...
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71 views

Connecting two Rohm KX224 sensors over I2C

I would like to connect two identical sensors (slaves) over an I2C bus. The problem is that they have the same address. The datasheet says the following: The KX224 Slave Address is comprised of a ...
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24 views

Not able to read impedance from AD5933 Eval board using Arduino

I am trying to read impedance information from the AD5933 evaluation board using an Arduino Nano BLE 33. According to the information provided here (https://ez.analog.com/dds/f/q-a/29168/how-to-...
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1answer
38 views

I2C Shifter being used to protect against short to much higher supply rail

For a device I'm retrofitting, there is a risk that some I2C datalines could be shorted to a supply rail that can be between 12-44V, or ground To the best of my understanding this bodge circuit per ...
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54 views

SMBus ARP working example

I've been playing around with an arduino and a few sensors when I came across this amazing communication protocol I2C with which a master can communicate with all of the sensors (or slaves in a more ...
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Xbee 3 coordinator not receiving packet from router transmitting data from I2C sensor

I have an XBee 3 router connected to a BMP280 sensor, running a micropython script which is supposed to send pressure and sensor data to an XBee 3 coordinator. This is as per Chapter 4 in Beginning ...
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1answer
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Controlling actuators - SPI - I2C - OneWire

I never worked with one of the above methods but for my next project I have to. I already read a bit about it but would like to have some user experience data.( I ordered them already to test it ...
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1answer
77 views

LCD 16x2 (I2C) with FPGA (Altera Cyclone II)

this is the question, a few days ago I bought the FPGA Cyclone II development board from altera (I am a big fan of arduino and I have a variety of modules and others) at first I started studying ...
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Help identifying I2C EEPROM - top marking H250 2GB 2

I have a Fujitsu server (PRIMERGY RX300 S8) with a failed I2C EEPROM on the front panel PCB. I would like to order the correct replacement components, but I am unable to identify the exact series/...
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39 views

Can't connect SSD1327 I2C

I just recieved 2 OLED displays SSD1327 128x128 16bits, 1.5", but I can't connect them to my arduino uno R3. I first tried with the Adafruit library, set the address 0x78 as printed on the ...
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Is it likely that one I2C device is interfering with communication to other devices?

I have two I2C devices on a single bus, with different addresses. Let's call them device A and B. Device A always works, no problem. Device B only works (means responds to I2C messages) either if ...
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Connecting PSoC 6 EINK alongside another sensor on the same board

I am trying to figure out a way to connect a CY8CKIT-028-EPD E-INK display shield and a MAXREFDES117 heart rate monitor to the PSoC 6 BLE board. The E-INK takes the entire space on the board, ...
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1answer
53 views

SI5351 I2C clock generator breakout board not detected on raspberry pi 3

I've recently bought a SI5351A I2C breakout board on Aliexpress (This listing) for a project. I was trying to test the board using a simple breadboard, a couple of jumper wires and my raspberry pi 3 (...
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1answer
85 views

My itoa (c++)conversion has a problem

I am receiving a string of data via UART in PIC32, extracting and concatenating two of its bytes, dividing the result by 2, converting the resulting integer to a string and transmitting via i2c to ...
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2answers
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Is there something wrong with this irregular clock line (SCL) on I2C? ( Arduino board)

I am trying to get this ADXL357 eval board to work, in connection with either Arduino Uno or Due via I2C. Sometimes I get a connection and can read out data, however often there are problems with ...
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1answer
25 views

Do the high / low levels of an I²C slave's response have to be of identical voltage as the levels of the I²C master's message?

I've got an IC (a TDA7318) with an operating voltage of +9 V. It's gonna be controlled by a Raspberry Pi 3B (output signal voltage: V_high = 3.3 V). Now I'd like to make sure that the responses sent ...
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1answer
56 views

I2C multiplexing with SDA only

I need to multiplex 16 I2C sensors which all have the same I2C address. Can I multiplex those by multiplexing SDA signal only? And having SCL signals connected to all 16 sensors all the time time? I ...
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1answer
44 views

Solution to interface SD card with microcontroller using only 2 pins (I2C/SPI)

So I am trying to add an SD card to my circuit and unfortunately, all I have left are 4 GPIOs, but I was asked to try and find a solution to only use 2. So using 4 is a worst case scenario. I thought ...
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225 views

How does ethernet connection relate to communication protocols like SPI, I2C, UART, USB? [closed]

I am having a hard time understanding ethernet communications between devices. Does it use protocols like I2C or is it a unique protocol itself? Could two chips on the same PCB use ethernet ...
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1answer
102 views

What to do with unused open drain pins

I have a light sensor IC. I have 2 questions: The I2C Lines is connected between the microcontroller (3.3V domain) and the light sensor IC. The microcontroller is placed on a PCB and the light sensor ...
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33 views

Programming I2C devices with NV EEPROM

Some I²C devices like the MCP4728 DAC have a small EEPROM allow programming the I²C address (and other configuration bits). I know that in high volume can be programmed by the vendor, but for low ...
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2answers
145 views

SPD I2c Address for DDR4 SODIMM

While designing DDR4 SODDIM schematic for a mini-pc motherboard, I understood that I need to set an address to Serial Presence Detect (SPD) EEPROM so the CPU can identify the memory. While looking at ...
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100 views

If I use twisted pair cable for I2C, should I twist SDA with SCL or both with the ground/power?

I need to design about 1 meter cable for I2C communication. It contains 4 wires, SDA, SCL, ground and power. I plan to use the shielded cable with the shield grounded at one end only. It looks ...
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APDS-9253 reads all data registers as 0

I'm trying to read data from an APDS-9253 with an xmega. My i2c bus is working because I'm reading other devices without any problem. From the datasheet it seems at power-up the sensor is not ...

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