Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [pull-up]

Refers to pull-up resistors, which are commonly used to "weakly" pull a signal line to a high state. Use this tag for discussing pull-ups.

-1
votes
2answers
285 views

Using an external pull-up resistor vs INPUT_PULLUP

When would one would prefer to use an external pull-up resistor vs the internal: pinMode(fanPin, INPUT_PULLUP); Dredging through the forums and this site, the commonly recommended value for a pull-...
1
vote
1answer
28 views

Interpreting pull-up values Rp and Rpu in AM3202 (DHT22) datasheet [closed]

In the AM2302 datasheet at page 3, table 4, it gives min, typ and max values for Rpu (that the pull-up resistor as it says verbatim) being 30K, 45K and 60K ohm respectively. Elsewhere in the same ...
0
votes
3answers
157 views

Do I need a pull-up/down resistor for button LED circuit?

When reading up on how to make a circuit that turns an LED on when a button is held down, I keep finding people saying a pull up or down resistor must be involved, to avoid the flickering state of the ...
0
votes
3answers
304 views

Multiple I2C slave devices on Arduino - Pull-up values

This question is asked a lot and I've found many usable details on different forums regarding adding pull-up resistors on SDA/SCL lines. I know that only one resistor should be added on these lines ...
2
votes
2answers
868 views

How can I tell the resistance of an internal pull-up resistor?

I have a SparkFun ESP8266 Thing Dev board, to which I want to perform a digitalRead() on one of the GPIO ports. I'm using D15, and I'm configuring it for input like this pinMode(15, INPUT_PULLUP); ...
2
votes
1answer
69 views

FSR wiring using internal pullup resistors?

What are the disadvantages to using Arduino's internal pullups with a force force sensitive resistor (FSR) sensor? All the wiring examples I see for FSRs place the sensor on the high side and use a ...
-2
votes
1answer
677 views

Arduino UART (TX/RX) multidrop 1 master 50 slaves

I'm thinking to connect about 50 slave Arduinos on 1 master using TX/RX. I'm following recommendation of these links: I'm looking for a way to serially communicate with a multi mesh Arduino slave ...
0
votes
1answer
1k views

ESP8266 light sleep - can't wake up

I am attempting to implement a light sleep mode on an esp8266 (feather huzzah) which, when a button is pressed, wakes the system up so that it can continue its normal task. I cobbled together some ...
0
votes
2answers
1k views

Minimum value I2C-pull up resistor for arduino

I'm trying to determine the minimum value of pull resistor for Arduino Uno The datasheets says for arduino; VOL = 0,4 for IOL = 20 mA. (VDD = 5V) For formula for calculation of minimal pull-up is: ...
0
votes
2answers
470 views

interrupt pin of attiny85 unstable

I'm trying to learn how to program a MC, so maybe I didn't know much about a MC. I tried to test interrupt pin of ATtiny85 with this simple code #include <avr/io.h> #include <avr/interrupt.h&...
4
votes
1answer
5k views

Resistor pull-ups for ESP8266

I'm using 4.7kOhm resistor as pullups for GPIOs 2,0,2,16, CH_PD and RESET, and also 4.7kOhm pulldown for GPIO 15. The ESP8266 boots and works fine. Would it be okay for a long shot? Should I use ...
0
votes
1answer
50 views

Digital Inputs have gone crazy

My digital inputs are behaving as if they were floating, even though I've properly connected them with a resistor. I've tried the pull-down configuration pictured below, as well as a internal pull-up....
0
votes
1answer
156 views

In a circuit with a switch and a pull-down resistor, why does the high impedance of the input not discourage current from flowing into pin?

I'm a beginner to Arduino and circuits. I've spent the last couple hours hung up on the concept of how current flows through switches and pull-down resistors, having read every thread and watched ...
0
votes
1answer
2k views

digitalRead not reading input pin of ESP8266-01

I am trying to use a on-off switch with the ESP8266 to change whether GPI02 is HIGH or LOW. I am using GPIO3 as input. My circuit looks like this: The red area to the right is a relay, I wasn't sure ...
0
votes
1answer
235 views

How do I pull up D1-D6 using 10k ohm resistors?

I'm using push buttons to control CR servos (button1=turn CW; button2=turn CCW). How do I pull up D1-D6 and what does that do exactly? I can't find a tutorial that explains it well enough how to use ...
0
votes
1answer
209 views

How do I stop 5v on the I2C port of a pro mini so I can use 3.3v devices?

The theory is that you can use 3.3v I2C devices from a 5v device as long as the pull ups are only to the 3.3v. I have a 5v pro mini connected to a bmp180 board which has a 3.3v regulator but no level ...
4
votes
2answers
583 views

Does an I²C IO Expander needs additional resistors for outputs?

I have following setup (see also schematic in the end) Arduino Nano is connected via I²C to the PCF8575C (link) IO Expander. Both, SCL and SDA have 10kOhm pull-ups to 5V. The Expander pins are ...
0
votes
1answer
750 views

Reading digital port with pullup via Firmata

I've got a weird issue, probably something I'm missing but have no clue what. Got some simple float sensors connected to D2 - D5 on a Nano. Need internal pull-up to eliminate a floating value. Wrote ...
5
votes
1answer
413 views

Shift Register w/ Internal Pullups?

Is there a chip that is just a parallel in / serial out shift register but with integrated internal pullups? I could use a full-blown I/O expander but I really just need more momentary button inputs. ...
0
votes
2answers
78 views

Digital Pin State - Some 1, Some 0

I'm running a sketch that looks for inputs to digital pins 3, 4, 5, 6, and 7. The gist of the sketch is that it's a digitalRead() from 3-7 with a Serial.println() to the monitor. The odd thing is ...
0
votes
1answer
1k views

Second I2C address not accepted

I have set up 2 DHT22 sensors and 2 BMP280 sensors with an Arduino Uno SMD R3 board. The DHTs are working fine and are outputting correct temperature and humidity values to the Serial monitor. The ...
2
votes
1answer
5k views

ATtiny85 and INPUT_PULLUP

I have read some conflicting sources about what pins have internal pullup resistors available for the Attiny85 microcontroller. Can all I/O pins work with INPUT_PULLUP, or just some of them? And if so,...
5
votes
1answer
3k views

ArduinoMEGA: 64 digital inputs cause random digitalRead values

I have 64 hall effect sensors (magnetic field sensors) (DRV5023AJQLPG) connected to an Arduino MEGA 2560. For that, I use 48 digital pins and 16 analog pins as digital input pins. The program in the ...
0
votes
2answers
1k views

Relay module and internal pull-up resistors

I'm currently assembling a prototype of the lightning infrastructure (based on several MEGAs interconnected via RS485, as described in this other post) The prototype consists of three MEGAs, a ...
0
votes
1answer
324 views

Use TSL2561 and DS1307 RTC together

I want to use a TSL2561 light sensor and a DS1307 RTC and a couple of other sensors like DS18B20, AS3935, ML8511, MQ135, 433 mhz sender together with an Arduino. However on Adafruit I read this today (...
1
vote
2answers
7k views

Disabling i2c internal pull up resistors

How do you do this? I've been digging around and I can see that I should do this and supply my own external pull up resistors but I don't know exactly how to disable them. The pages I've been reading ...
2
votes
1answer
594 views

Using an Arduino as an LED controller for an arcade stick

I'm attempting what seemed to be a rather simple problem at first glance, but due to my limited knowledge of Arduino workings I need some help. I'm trying to use button outputs from a PS360+ arcade ...
1
vote
4answers
1k views

Testing tri-state pin - erroneous results with internal pullup

I'm using an MPC73831 - a LiPo charging IC - in my Arduino project. It has a status pin to allow interface to a microcontroller, which uses a tri-state operation to convey three possible states of ...