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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348 views

Single I2C EEPROM 24C02 uses all eight addresses by itself

I was scanning for a used address by I2C EEPROM (24C02). Contrary to my expectations, it returned all eight possible addresses (0x50-0x57) instead of the hardwired one. I thought the problem was in a ...
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108 views

Multiple slave I2C on different power rails

I read following threads, but still there are some unclear parts for me. Multiple I2C devices with the same address I2C Pull-ups with Multiple Power Supplies Design for Multiple I2C slave devices I ...
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121 views

I2C bus line over different layers in an arc

I have the following board design in mind: It's a 4 layer, ~5cm diameter board where 10 slave PCB's will be soldered to it that are connected over the I2C bus. The trace line you see is roughly 8 cm ...
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196 views

OSError: [Errno 121] Remote I/O error or pigpio.error: 'I2C read failed' on MPU6050

So I use MPU6050 to get acceleration from stepper motor linear rail movement(steper motor working in thread, I use pigpio for the motor) by make the MPU6050 can work on threading and it can show data ...
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106 views

How to correctly send the data I received via I2C over UART?

I am using an atmega328p and writing firmware to display the data I receive via i2c in putty. I read the data I receive as follows: ...
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108 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 ...
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68 views

Write collision for multiple reads - PIC24 I2C

I am trying to poll a CAP188 sensor so I'm sending it read commands in a while loop, but the first read works and then on the second read when I send the slave address it detects a write collision. ...
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638 views

At what edge of the clock, SDA signal is sampled in I2C for data? At rising edge / falling edge / after rising edge?

I found this from wikipedia page. It says, data is sampled after SCL line rises.
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98 views

Just read a Register

I am using a STM32F103CBT6 as I2C Master. After sending the I2C Adress of the Slave I need to clear the Addr bit in the SR1 register. The Datasheet states: "ADDR: Address sent (master mode)/matched (...
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182 views

What does it mean when i2c_smbus_read_byte() returns 0

i2c_smbus_read_byte() returns a negative value when there is an error in reading data. But what if it returns 0? Following is the code from adt7316-i2c driver ...
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69 views

I2C pullups for level shifting

If I want a breakout with two sensors on it, one operating at my MCU's voltage (3.3V) and the other requires a drop to 1.8V, do I need two sets of pullup resistors for both voltage lines? Can I do ...
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98 views

Problem I2C reading RA8875 using TM4C123

I have been working with I2C protocol to create some code for the RA8875 (see for I2C from page 67) using a Tiva board (TM4C123, I2C chapter from page 997), and I was able to paint in the display or ...
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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 ...
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1answer
139 views

I2C: Trying to read multiple registers, getting first register repeated instead

I´m trying to read registers 0x28 through 0x2D from the L3G4200D (gyroscope, datasheet), which is part of the GY-80 board, using the esp32 (I2C info) as a master, which is part of the LOLIN32 board. ...
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301 views

AVR Can Write I2C, but Fails to Read (Fails to Write Register Address)

I'm using an ATMega328 DIP Package with a TLE493D(A0) (and manual) 3-axis hall effect sensor. I've done successful reads/writes to other I2C devices (AT42QT2120), but I'm having issues with the TLE493....
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338 views

I2C driver for MSP432

I am trying to develop a I2C driver for MSP432. As of now, I am interfacing a accelerometer through USCI B2_ module on MSP432. The problem that I am facing is I am getting a NACK in the IFG register ...
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588 views

I2C Scanner not working properly

First of all, please see my other question HERE as it is related (Any help with that is greatly appreciated too). If you read through my other question, you will know that I am attempting to ...
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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 ...
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BLE Nano I2C on P0_10

I have a project where an nRF51822 (BLE Nano v1.5) is an I2C master and communicates with an Atmega328. I have communication working over I2C just fine using various pins. However, when attempting to ...
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2answers
1k views

How to read data from this sensor?

I am using the MLX90393 Magnetometer IC from Melexis. More specifically, I am using the breakout board by Sparkfun. I am still a beginner when it comes to programming, and this is my first time trying ...
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I2C line pulled low by MCP23017

A simple interface of MCP23017 with Rpi using I2C lines. Since there is already an internal pull-up resistor of 1.8k on rpi I didn't use any pull-ups n I2C lines. Running ...
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951 views

Relationship between I2C drawn energy / power consumption and data rate

Referring to just what the I2C lines draw, am I wrong thinking that the higher the clock frequency the shorter the time there will be (the same amount of) current flowing through the pullups and thus ...
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1answer
111 views

MS5611 sends additional byte after NACK

I'm currently try to use the MS5611 (sitting on a CJMCU-117) over I²C with libopencm3 on a STM32F103C8. When I do a read, the slave sends an additional byte (0xFF) after the master has send a NACK. ...
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How should I used two MLX90614 sensor on one Arudino Uno given that the sensor has a fixed I2C bus adress? [duplicate]

I have an arduino uno and want to use a non MLX90614. I plan to used more than one sensor on the same Arduino but I don't know how to use two MLX90614 on the same I2C bus.
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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 ...
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3answers
183 views

What exactly are low speed devices? [closed]

The definition of I2C is - "A multi-master multi-slave serial bus used for communication between low-speed devices". However, I have been searching the web for a concrete explanation for this but ...
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1answer
167 views

Daisy chaining I2C modules using CAT5 and P82B715

I'm planning to connect several modules over I2C with distances between modules ranging 30-180 cm. I understand that in order to avoid the degradation of the signal due to the capacity of the ...
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1answer
99 views

I2C Pulldown Resistor

Usually pullup resistors are needed for i2c but if I have pullups in master and hosts devices and when I add another one device to I2C bus then bus stop working. I cann't remove pullups. Does it make ...
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4answers
661 views

UART expander (5 ports to 11 ports)

I have a board that I would like to design and there are 11 devices that can only be spoken to via UART. I am restricted to a Microchip uC chip product range and I have found one with 5 UART ports. I ...
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343 views

STM32F103C8T6 - I2C communication with TI FuelGauge BQ78350

I am trying to establish communication between TI BQ78350 FuelGauge and STM32F103C8T6 using I2C/SMBus. The following is the I2C configuration used for the standard HAL I2C library. ...
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147 views

i2c bus sniffing and spoofing

Some Background: I am working on an embedded c project for a samd21j18a MCU. The MCU communicates with 2 crypto eeproms on the i2c bus. All the data is encrypted with AES in CCM and additional ...
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106 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 ...
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3answers
743 views

I2C Issues - SCL is stuck high [duplicate]

I am working on a custom carrier board using a TI microcontroller as the master and an ADC IC as the slave. It appears that sometimes SCL will stay high when it shouldn't, almost like the master ...
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1answer
56 views

How does integrated displays controlled by the computer?

Consider a run off the mill pc: lcd displays connected, you have brightness control in the menu of the lcd. And some other stuff like color temp and modes. Now consider a laptop, AIOs and kiosk PCs. ...
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120 views

LCD leaking power through I2C cables

Background I have a NodeMCU and two LCD devices and an ADS1115 on one I2C bus. The LCD devices have I2C backpacks. The NodeMCU is on 5V USB power and internally operating at 3.3V. The other devices ...
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152 views

ESP8266 sleep current is higher than it should be [closed]

In short: Despite setting my datalogger IMU to SLEEP and going to deepSleep(0) on the ESP without any other IC peripherals besides the buck converter and 2 deactivated LEDs, I still measure 2.5mA ...
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1k views

Is this communication I²C?

I need to decode communication between two devices, but I have no information about these devices. All I know is that four wires are needed (GND, VCC and two wires of communication). I suspect that it ...
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130 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 ...
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1answer
195 views

I2C slave device model for testing?

Has anyone come across a real manufacturer-supplied device model that I can use for testing an I2C master, in VHDL or Verilog? I've had a look through the Opencores slave models, and the testbenches ...
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295 views

I2C response to “Ghost Address” 0x5F

I recently bought a ZS-042 RTC module which communicates using the I2C protocol. The module includes a DS3231 (RTC) and an AT24C32 (4k EEPROM). The ZS-042 module has no datasheet, but the Ebay ...
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182 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,...
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130 views

I2C device lists 20mA max current on AD, CL, and DA pins. Do I need a resistor between it and Arduino?

I'm looking at the datasheet for an LED controller (the MAX6955), and it shows that all of the interface pins; clock, data, address, etc., have current maxima of either 20 or 40mA. I'm aware that the ...
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2answers
176 views

VL6180X ALS values soo small

I have bought VL6180X proximity sensor on breakout (Aliexpress) originally designed for use with arduino. I have tried it use with Raspberry Pi and STM32 (on STM32F429 discovery board). Sensor is in ...
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322 views

Debugging I2C, Effect of Oscilloscope Probes

Working on a simple I2C setup: Raspberry Pi connected to a WM8731 audio chip. The Raspberry Pi configures the WM8731 (which is write only) over I2C. Problem is WM8731 doesn't always respond with ...
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212 views

Can I use a Dupont cable with a resistor soldered in the middle as a pullup resistor for I2C comms?

The short question: is there a difference between using (on a breadboard) a standard through-hole 10K pullup resistor, versus using a modded Dupont cable with a 10K pullup resistor soldered in the ...
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50 views

How are bits put on a bus, the i2c for example?

I have been to school and through these topics, understand that "bits on a bus" is a behaviour emerging from the very way a CPU works. But still, I suppose this requires some interaction... it doesn't ...
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63 views

Does the Si4731 / Si47xx provide the necessary info to fetch left/right demodulated audio levels?

I'm working on a project which uses an Si4731 broadcast radio receiver IC (Si47xx family) and which calls for left & right demodulated audio level meters based on a source FM broadcast signal. I ...
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307 views

I2C design with secure message

Is it possible to secure I2C communication between slave and master so nobody else can connect their devices to the master. Basically encrypting the message. Is this feasible by software or hardware?...
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131 views

How can I enable a LDO using the I2C SCL signal

Can I enable/disable an LDO (more specifically NCV8163AMX280TBG) by using the I2C SCL signal? This would allow me to turn ON the regulator once a master starts the I2C protocol and turn it off once ...
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109 views

No signal output on I2C bus

I have an ESP-WROOM-32 (I2C master) and an ATmega328p (I2C slave, address 0x03) assembled on a prototype PCB using external 6k8 pull-ups. I'm using the ESP's default I2C pins 21 (SDA) and 22 (SCL) as ...