Linked Questions

10
votes
5answers
5k views

Considerations when using internal pull-up/down resistors

I am working with STM32 micro-controllers. These micro-controllers have the option to set the input pin as pull up or pull down: Earlier I used to give external pull up or pull down resistor wherever ...
15
votes
3answers
2k views

Why do we need external pulling resistors when microcontrollers have internal pulling resistors?

Microcontrollers do have internal pull up-pull down resistors yet most of the circuits have external pulling resistors. I looked on Google for answers and a few sites said that those resistors are ...
7
votes
2answers
2k views

Optional pull-up resistors for I²C

I need a circuit that would allow me to optionally add pull-up resistors to an I²C bus. One way would be to add two jumpers for each pull up resistor. But I thought of something like this: This way ...
8
votes
2answers
5k views

How to deal with multiple pull-up resistors on modules

I was thinking about doing a modules for a development board I did a few days ago that will include spi/i2c interfaces. The problem is that I didn't included pull-up resistors in the MCU pins in the ...
7
votes
3answers
10k views

How is the clock frequency established between master and slave in I2C protocol?

This is a follow-up question to What happens if I omit the pullup resistors on I2C lines? In a digital wall clock I designed (using the DS1307 RTC and the ATmega328 MCU), I accidentally omitted the ...
1
vote
3answers
1k views

Can I do without I²C pull-up resistors?

I am trying to produce a small circuit, and I am looking to reduce the part count. I recently added an I²C EEPROM which is used once when the system boots up, along with this EEPROM I added two ...
3
votes
2answers
2k views

Using internal pull-ups for I2C on PIC18F

I'm working with a PIC18F46J53 and it was working quite well without any troubles. Suddenly, I found a hindrance on my path. I used RB4 and RB5 pins as I2C bus pins for communicating with an EEPROM (...
4
votes
1answer
2k views

Problem using DS1337 - RTC

I am trying to use a edited version of the library given at this link. I basically changed some of the included file and some of the changed function of the wire.h library. Though I am not a hardcore ...
1
vote
2answers
4k views

How to isolate two ground signals?

I'm have grounding problems (80% sure of it). I have an MPU6050(gyro sensor which works on 3.3V) which is powered by the Arduino's 3.3V pin and SCA,SCL,INT pins are used with the I2C bus of the ...
-4
votes
1answer
815 views

Can I2C work without pull up resistor?

I'm working with nrf51 board, I'm using I2C to communicate with an accelerometer (see the scheme), the communications are successful but I dont see any pull up resistors in the lines ...
0
votes
3answers
835 views

I2C data line not having correct voltage levels

I've been working on a project with a EFM8UB1 development board and ATECC508 I2C peripheral. Everything works fine but I'm having problems with I2C when moving to a PCB. Here is a trace of the clock ...
1
vote
1answer
361 views

FXOS8700CQ - Arduino core I2C doesn't work, SoftI2C does

I use the Arduino core libraries in my latest project (ATMega328P MCU) I'm trying to talk to an FXOS8700CQ via I2C. Reading register 0x0D should return 0xC7. The typical Arduino Wire library method, ...
0
votes
1answer
311 views

MCP23017 with NODEMCU v3 (lolin) i2c doesn't work

I want to use NodeMCU v3 with MCP23017 that has MAX6675 at the end. Everything is on circuit please see the image. MAX6675 (U3) doesn't want to work with MCP23017. First MAX6675 (U4) works perfectly ...
0
votes
1answer
143 views

Running Bus at Low Speed- I2C bit banging

I am implementing I2C using Bit bang. The slave can accept maximum baud rate of 400kbps. Iam not using external pull up, which is required because of which the fall/rise are not accordingly. I read ...
0
votes
1answer
129 views

MS5611 Barometer not working on PCB design

On a recent project of mine, I incorporated an MPU 9250 and a MS5611 Barometer on the i2c bus of an atmega 32u4. The MPU 9250 works perfectly, but as soon as I solder on the MS5611 neither of them ...

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