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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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67 views

Long-Distance Multi-Slave Communication

I am currently trying to connect many serial slave devices to my Arduino device over a 14 meter distance. I am looking to have slave-to-master communication. These devices include: 3 BME280 ...
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2answers
93 views

What is the triangle components in this diagram?

I am reading through datasheet of a voltage translator for I2C (FXMA2102) and I cannot understand the triangle components in the block diagram: Are they diodes to make current flow in one direction? ...
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1answer
85 views

Detect an unknown communication protocol and read data on it

We have old type textile machinery in our factory. (open end machine) on the machine's screen is showing the operating efficiency of the machine. Under the hood, When I follow the cables, the sensors ...
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1answer
92 views

Distance between UART and I2C bus

I create a board with two bus: UART and I2C. Now I am expanding the connection terminal, which has the following contacts: RX / TX / SDA / SCL / + 5V / GND. The question is, do the I2C and UART buses ...
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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 ...
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118 views

How to generate NACK on STM32F407

Is there a way to send a NACK on I2C on STM32F407? There is no way to do that using the HAL, and the datasheet says nothing about it.
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1answer
61 views

FMPI2C on STM32F407

Is it possible to use Fast mode I2C on STM32F407 ? I looked everywhere for the I2CX pins GPIO but Can't find them at all.
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65 views

Interfacing A71CH with I2C

I'm trying to interface the following chip with STM32F4 https://www.nxp.com/docs/en/supporting-information/AN12207.pdf I'm currently trying to transmit a repeated start using hal sequential ...
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85 views

Checking my mpu6050 schematic

I am fairly new to pcb design and I just created a mpu6050 chip that will work with an Arduino microprocessor. I want to make sure the hookup is all correct before I start work on the other parts, as ...
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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 ...
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1answer
59 views

I2C master and slave use different power sources

I have two slaves on the I2C bus. Before, both master and slaves used the same power source (2.8V), and the I2C bus works fine. Today, I changed the master to another power source (3.3V), keep the ...
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1answer
29 views

TCA6408ARGTR input inversion trouble

I'm curious, Has anyone used this http://www.ti.com/lit/ds/symlink/tca6408a.pdf part? I just tracked back a sign error to the read values remaining active low after I set the inversion register on ...
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1answer
133 views

PIC I2C communication problem with I2C multiplexer

I need to read data from 3 of the same kind of batteries with SMBus so I decided to use an I2C multiplexer for this purpose. I can communicate with 1 battery without any error. But I cannot ...
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2k views

Can only the master initiate communication in SPI whereas in I2C the slave can also initiate the communication?

Is it possible for a slave to initiate communication in SPI? I thought due to the chip select i.e. NSS feature only master can communicate the communication. However, in I2C, the slave can also ...
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2answers
133 views

How to verify a VHDL I2C master?

Once an I2C master has been written, the next step is verification. Provided that a BFM for the slave does not exist, how should one go about doing this? Also seeing how I2C is open collector in ...
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1answer
65 views

Multichannel Design with Multiplexers

I am trying to use four MUXes to send 4x8 identical sensors onto an I2C bus. Let's call my four types of sensors A,B,C,D. Eight of each means 32 sensors that I need to 8:1 MUX onto one I2C bus. I'm ...
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42 views

Voltage drop after writing to slave register with I2C protocol

I'm trying to control this bipolar stepper motor with an Adafruit Huzzah32 (ESP32) board and a stepper driver shield. Power sources: ESP32: 5V USB port Shield: 4 AA-batteries in series I ...
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2answers
144 views

I2C sometimes works sometimes doesn't

I am trying to troubleshoot communication between Arduino (master) and 3 slave sensors (VL53L0X): Below is VL53L0X sensor module I am using. I checked and confirmed that the placement of resistors ...
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1answer
193 views

Problem getting board to board I2C communication to work on STM32

I have two boards working on STM32F030R8 and F030C6 respectively. I have been trying to get the boards communicate with each other using I2C but so far, no good. One of my boards run at 48MHz and the ...
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1answer
63 views

I2C communication between MPU6050 and MSP430FR2433

I'm trying to communicate in I2C between a MSP430FR2433 and an MPU6050. I can send the start bit then the slave address (0x68) followed by the write bit (0) but the slave send me a NACK. I'm using the ...
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66 views

PIC24F debugger halts and resets upon I2C read of slave

I've been trying to debug my I2C communication between the PIC24FJ32GA002 and the PCA9546APWR bus switch for a couple of days now. I just want to test that I could enable a channel of the bus switch, ...
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1answer
47 views

I/O expanders- CAN & I2C

Currently in my system we use 16 I/O expanders with I2C interface. I want to change it to CAN interface. Which is the best possible way without compromising the cost? I tried searching for 16I/O ...
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105 views

Communication via I2C sensor via CAN bus

I am wondering if it is possible to implement the following idea: I want to build a network of sensors, all of them communicate via I2C protocol and all those sensors will send their parameters via ...
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1answer
77 views

OLED ssd1306, “Set the Oscillator Frequency”?

I am working with a OLED SSD1306 and in the datasheet there is a parameter named "Set the Oscillator Frequency." It is a four bit value to adjust. I can't understand the purpose of this. Can ...
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2answers
86 views

Can I use one pin as I2C clock or data AND as GPIO?

It happened to be that I run out of pins on ATmega48PA. So I have a pull-down buttons on the pins dedicated for I2C: And now I need to add I2C bus to this device with as much backward compatibility ...
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1answer
95 views

Unable to Read BME280 using TM4C123 LaunchPAD

I'm new to the Tiva Platform for the past two days I'm trying to read data from bme280's data registers. However, it always returns a 0(I2C bus not working). So far I've tried using this sensor with ...
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600 views

STM32F3 I2C hangs on busy flag (interrupts)

I am using two STM32F303K8 Nucleos and hooked up the SDA/SCL (GPIO B PIN 6 & 7) pins to 3.3V across roughly 4.7K resistors to 3V3. When I check the voltage on the pins, both are 3V3 so it's not ...
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1answer
78 views

Disadvantage of using low resistor value for pull up (Strong pull up)

I was trying to choose a resistor value for a pull-up resistor I will use in my project. The project will have I2C communication and SMBus communication. When I was searching on the internet, I have ...
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1answer
48 views

A question about the Clock control register high of I2C bus

While reading the part about I2C bus of reference manual of STM8L MCUs, I found that there is this register named Clock control register high (I2C_CCRH). Its 6-th bit, referred as "DUTY", can be used ...
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1answer
246 views

PIC18F47K42 I2C Slave MCC code incrementing register by accident

Disclaimer: I have submitted a forum post on Microchip as well as the forum appears to have issues with me and to increase the pool of possible answers I thought of posting here with as much detail ...
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99 views

I2C multiplexer channel selection and pull up resistors

I need to communicate with 3 batteries through SMBus. I managed to communicate each of them separately one by one. However, I need to communicate with 3 of them, for that I decided to use multiplexer. ...
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1answer
172 views

STM32F746 - DISCO I2C HAL_TIMEOUT

I am attempting to implement I2C interface on the STM32F7-Discovery Board using the a VEML 6070 UV light sensor (https://www.vishay.com/docs/84277/veml6070.pdf). The 7-bit slave address for the ...
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1answer
97 views

How can I isolate an ATTiny from an I2C slave so ICSP will work?

I'm building a small circuit to blink some LEDs with an ATTiny. I'm planning to use a 16-channel LED driver and talking to it with an ATTiny over I2C. I'd like to use a SMD ATTiny and add some test ...
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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. ...
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3answers
191 views

I2C weird data and clock output/input

Hello I am trying to communicate that is using SMBus. So when I try to send a data which was 0x0D and address of the device was 0x16. I see something like that on the data line: And this is how my ...
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2answers
269 views

SMBus pull-up resistor value

Hello I need to communicate with a device using SMBus. However, I could not choose correct value for pull up resistors. Vdd is 4.9V and I use SMBus. In same conditions for I2C communications I used 2k ...
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44 views

PIC I2C clock related problem

I am trying to make an I2C communication with a device by using PIC18F26K83. I use 8 MHz MCU clock. While trying to set I2C clock these options: Use 8 MHz MCU clock & HFINTOSC for I2CxCLK ...
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165 views

STM32f103 interfacing with adxl345 via i2c

I am working on interfacing ADXL345 accelerometer with STM32F103 blue pill board through I2C communication. I have written the code in Keil software by surfing the internet which works fine sometimes, ...
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1answer
34 views

I2C bus stopped working when power was switched to battery

Let me try to describe my schema: There is 12V acid battery constantly charged with DC 13.8v 500ma, on that power (battery) is connected attiny85 thru 78l33 voltage regulator + capacitor 470uf, thru ...
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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 ...
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1answer
58 views

PIC I2C Clock selection

Hello I will be communicating with a device using SMBus. For this, I will be using PIC18F26K83. Timing is not important for me so I m somehow free to choose any clock frequency for my MCU. Well higher,...
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1answer
1k views

IC has pull-down resistors on SMBus lines?

The datasheet of TI bq40z50-R2 (Li-Ion Battery Pack Manager) tells that "The SMBus clock and data lines have internal pulldown". Pin equivalent Diagram is in image below: Aren't usually the SMBus ...
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1answer
80 views

PCF8591 I2C Problems on Raspberry Pi

I am using 3 PCF8591 ADC connected via i2c to a raspberry pi. At first all 3 of the ADC worked. All of a sudden I started having issued with them. Occasionally one of the i2c devices stops showing up ...
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1answer
114 views

PIC I2C PPS mapping

I will be communicating with some device via SMBus. I use PIC18F26K83 and I will use RB1 and RB2 pins as SCL and SDA pins. My question is about PPS mapping. In datasheet it says that I need to set ...
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1answer
108 views

Serial Peripheral Interface (SPI) vs Two-Wire Interface (TWI, I²C) wire length

I'm using Arduino DUE to read data from an IMU(inertial measurement unit) sensor (MIKROE-1577, MPU-6000) This IMU sensor supports both Serial Peripheral Interface (SPI) and Two-Wire Interface (TWI, I²...
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1answer
112 views

How to explain and possibly avoid undervoltage on I2C bus?

I've been testing different sensors for the I²C bus with two host devices: Raspberry Pi 3B (3.3V), and Sitec S4 (5.0V). Since one of them, namely the Sensirion SCD30, had communication problems every ...
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1answer
85 views

SMBus: Is 100 kHz clock a risky frequency?

I will communicate with a device via SMBus. I use PIC18F26K83 for this. In SMBus spec it says clock minimum clock frequency is 10 kHz and maximum clock frequency is 100 kHz. Would it be a risk to use ...
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0answers
104 views

TCA9548A (I2C multiplexer) works for a few minutes and then hangs

I'm having trouble getting the TCA9548APWR to communicate for longer than a few minutes. I'm only able to get it to "reset" by resoldering it. I have used both an Arduino Mega and a Beaglebone Black ...
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1answer
31 views

SMBus v1.1 voltage threshhold value

I am planning to use PIC18F26K83 and communicate with a smart battery that uses SMBus ver 1.1. So from the datasheet of PIC it says I need to choose appropriate input threshhold for SMBus from RxyI2C ...