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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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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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71 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
38 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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27 views

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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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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33 views

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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4answers
639 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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31 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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59 views

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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73 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 ...
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93 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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44 views

Unreliable I2C on ATTiny85

I am using an ATTiny85 as slave and STM32F103C8T6 as master. The address of the slave is 0x40. If the I2C cable, between the two devices is connected during power on, there is no ACK from slave when ...
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1answer
43 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
72 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
121 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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4answers
76 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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52 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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20 views

rfduino i2c no activity on bus

I've been working on RFD22102 RFduino with the USB shield. Using the board manager in Arduino IDE to retrieve RFduino package under the URL "http://www.rfduino.com/package_rfduino166_index.json" ...
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0answers
31 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
122 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
45 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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2answers
57 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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0answers
53 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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4answers
962 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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43 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
85 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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1answer
104 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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0answers
77 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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3answers
97 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
128 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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1answer
118 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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3answers
89 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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75 views

STML052K8U + DS3232: I2C not working

I have a problem, I use a microcontroller and RTC STM32L052K8U DS3232M and I can not connect via I2C with RTC, using the HAL library. From the watch constantly comes NACK. The wizard sends the correct ...
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2answers
46 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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1answer
33 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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100 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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78 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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1answer
62 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 ...
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43 views

What does the values of 0x10 and 0x08 mean for gyroscope MPU6050 registers?

I am trying to connect a gyroscope MPU6050 to arduino ATmega2560 and read its raw values from its 6DOF (gyro and acc). I found the following code: ...
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2answers
250 views

The use of redundant I2C in spacecraft avionics

I recently read this report about the JPL x2000 avionics development project, which developed more modular avionics platform using commercial silicon, to cut cost and power. They opted for an ...
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2answers
77 views

Choosing correct DAC: DNL and INL

let me know what I state below is correct or not. Regarding the DNL and INL of a DAC, DNL is the error difference between actual step width and ideal value (1 LSB). INL is the deviation of actual ...
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1answer
204 views

I2C bus occupied

I have a problem with an I2C communication and want you to ask whether there is a better solution than mine. I am programming an STM32F103 at the moment. There is one sensor (MPU6050) which is ...
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1answer
348 views

I2C IC for part identification

I am looking for a way for a host system to identify that a certain mechanical module C is connected to it. This mechanical module doesn't need to have any electronics in it, but due to host ...
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1answer
69 views

I2C & SPI - share clock lines?

I know mixing SPI and I2C is a bad idea, but, when using a microcontroller short on pins, is it safe to share clocks between both buses, provided both are running at bus-tolerable frequencies? In my ...
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1answer
161 views

Why do many uC have more then one I2C interfaces? [duplicate]

On I2C buses you can hock up 112 devices. So why do so many microcontrollers have up to four I2C ports, when you could just operate enough devices for most applications on one I2C interface?
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63 views

reading a bit from VCNL4010 sensor through I²C

I'm using the MSP430FR2433 LaunchPad. I'm trying to interface with a VCNL4010 sensor to my MSP device via I²C. After entering into Transmit(); I'm ...
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1answer
30 views

QT1070 inconsistent readings on touch pins

I recently transitioned my projects capacitive touch IC from using the MPR121 to the QT1070. I am getting irregular/inconsistent readings on one of the touch pins. In this particular situation, it ...
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1answer
176 views

stm32f401 I2C does not send byte after repeated start

I am programming an I2C master on a STM32F401 nucleo board. I program it without HAL, just using registers. I am interfacing a peripheral, that has to be read like the following: Start Write ...
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3answers
215 views

I2C slave not ACK'ing quickly enough

I am programming a microcontroller to talk with a slave device via I2C. My I2C transactions always get NACK'd, but I believe the slave is ACK'ing the transaction, just a little bit too late and my ...
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5answers
152 views

I2C monitoring without Microcontroller [closed]

I am trying to read data from an I2C connected touch sensor. Specifically the Azotec IQS266. I plan to preprogram all of the settings the way I want them, and then not touch them again after that. In ...