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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.

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Sketch halts if button is pressed on boot

I have a KY-040 rotary encoder with a push button wired to an ESP8266. My objective is to be able to detect if the button is pressed or not on boot. In the below code, if I hold the button down and ...
Lachlan Etherton's user avatar
-1 votes
2 answers
377 views

Arduino Pro Micro not recognizing INPUT or INPUT_PULLUP

I tried to make a controller box with multiple buttons. Sadly, when I tried to connect the buttons, the Arduino Pro Micro didn't recognize them being pressed. I even tried to connect a wire directly (...
szilard1996's user avatar
2 votes
2 answers
292 views

Barebones AVR - Connecting RESET pin to Vcc

I want to build my first barebones AVR circuit. I plan on NOT having a RESET button. For this reason, is it valid if I connect the ATMEGA's RESET pin to Vcc directly? What I mean by this, is that in ...
user1584421's user avatar
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1 vote
0 answers
33 views

Poor Contact and Low Current Issues with Microswitches in Arduino USB Game Controller

I have made a USB game controller using the Arduino Micro and Omron microswitches (VX-01-1A3) for the buttons. The switch is wired with one end connected to a digital pin and the other end connected ...
gon weigang's user avatar
0 votes
0 answers
169 views

How to work with a pulled high input pin where it needs to read a value from an analog sensor?

I have a small ESP32 module, that has some in-built features, like a TFT, and has few available pins for general use. It has some input only pins (GPIO36 to 39) that are used by buttons soldered in ...
Rodrigo's user avatar
  • 113
1 vote
1 answer
131 views

Will I need the internal pullup resistor if no button is used?

Given I have two Arduinos that are supposed to primitively communicate with each other using digital pins. On Arduino Ar1, pin D13 is to be used as an input, connected to Ar2's D2 pin. Will I need to ...
Mikoyan's user avatar
  • 33
3 votes
1 answer
612 views

Input Oscillating Wildly

I'm trying to read an input from a switch but instead of getting 0 and 1 for closed/open, I'm getting 0 and a rapid series of 1s and 0s. Originally I tried (and failed) to simply read a rotary encoder ...
WillM's user avatar
  • 39
0 votes
1 answer
102 views

DS1337 with shared I2C pull-up

I have a project using an ATMEGA328P and a DS1337 RTC chip. The DS1337 is an 8 pin IC with VCC at pin 8 and GND at pin 4. According to the datasheet both pin 5 (SDA) and pin 6 (SCL) need an external ...
jhorv's user avatar
  • 41
0 votes
1 answer
402 views

I2C pull up resistors and an I2C MUX

I have a rig with 5 light sensors on an I2C mux and I am wondering if I need only 1 pull-up resister set for the whole bus or one on each branch from the mux? Or should I remove all the pull-ups from ...
levi Clouser's user avatar
1 vote
1 answer
146 views

How to test custom cables?

I'm trying to make a cable checker to help me make custom cables for my computer. I'm thinking I plug the cable ends into sockets on the device, then the Arduino checks between different pins to make ...
Eggo's user avatar
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3 votes
4 answers
2k views

Can internal and external pull up/pull down resisters be used together?

What happens if a sketch uses code like pinMode(18,INPUT_PULLDOWN) to configure internal pull-down (or pull-up) resistors, but is used in a circuit where external resistors are also present? Are there ...
JRI's user avatar
  • 200
1 vote
0 answers
49 views

Reading ground signal from circuit

I am trying to detect whether a signal is high or low from an ESU LokSound 5 decoder for HO locomotives. My idea was to use one of the auxiliary pins used to drive an LED (AUX 3 in my case). The ...
DuluthIsSuperior's user avatar
0 votes
1 answer
417 views

What is happening when digitalWrite(pinname, LOW) is invoked after pinMode(pinname, INPUT_PULLUP)?

I read the Arduino official docs on digitalWrite and am confused about what is happening from an electrical perspective when digitalWrite is invoked on INPUT_PULLUP pins. Say my code says this: ...
rfii's user avatar
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1 vote
1 answer
405 views

Current difference between pinMode(pin, INPUT_PULLUP) and digitalWrite(pin, HIGH)?

Does pin 5 or pin 6 use more power if they're just being used as a signal to an external device? pinMode(5, INPUT_PULLUP); pinMode(6, OUTPUT); digitalWrite(6, HIGH); . EDIT: Thanks to some links ...
rfii's user avatar
  • 170
0 votes
2 answers
112 views

Detect if a display is connected

I want to detect wether a display is connected or not. This is the display: https://www.az-delivery.de/en/products/1-77-zoll-spi-tft-display I read connecting a pin of the display with another pin ...
Joh's user avatar
  • 113
2 votes
1 answer
3k views

Can't Turn Off Internal I2C Pull-Ups on ESP32

I've designed a custom ESP32 board around the WROVER-IE module. To keep power low, I'm using a GPIO-controlled high-side FET to turn off unused peripherals when in deep sleep mode. The issue: I've ...
Nick Johnson's user avatar
1 vote
1 answer
47 views

Unable to make a really basic sketch work

I've been learning how to encapsulate my code within functions, and one of the examples I worked on is a simple INPUT_PULLUP button. When I upload the sketch from the arduino website everything works, ...
Zhelyazko Grudov's user avatar
1 vote
0 answers
274 views

Arduino pull-up resistor not working

I made a circuit where when I press a button, a LED lights up using a pull-down resistor. But when I tried the same with a pull-up resistor instead, the LED remains off (whereas I expected it to be on ...
lizardsudoku's user avatar
2 votes
1 answer
869 views

Configure input pullup through registers

I can set pin mode to input or output through the DDRx registers. How can I enable the internal pullup resister through a register?
iHnR's user avatar
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2 votes
2 answers
2k views

Unable to use analog pins as digital inputs

I want to use the analog pin A7 as a digital input pin. As stated in the Arduino docs the analog pins can be configured in the same way like any other digital pin. However, when trying to configure an ...
albert's user avatar
  • 205
0 votes
0 answers
737 views

Wireless playstation 2 remote not connecting up to arduino

I am trying to connect my wireless playstation 2 remote up to my arduino but I am facing one problem. Whenever I restart my program (by clicking the red button) the PS2 remote's dongle blinks at the ...
DigitalRookie4's user avatar
0 votes
1 answer
584 views

i2c high speed and pull-up resistors

hello guys i want to ask about 2 things first one is i'm connecting and arduino uno attached to a usb host sheild and transferring data of a mouse coordinates to 10 arduino leonardo i'm using the ...
mohamed shalaby's user avatar
0 votes
1 answer
504 views

Using the LED pin for input

I have an Arduino-like device with few GPIO pins (DigiSpark clone). It is based on an 8-pin AtTiny85 IC so there are Power, Ground and six other pins, two of those six are being used for USB keyboard ...
RedGrittyBrick's user avatar
-2 votes
1 answer
1k views

Will a pull up resistor help the UART transmission accuracy on Arduino nano?

On A post from Arduino forum , someone mentioned that a pull up resistor over RX/TX pin could help the reliably of UART communication. Is that really the case for nano and uno board?
ShoutOutAndCalculate's user avatar
1 vote
1 answer
8k views

How many UNO pins have internal pull up resistors?

As the title implies. thank you in advance.
Abdalrahman Seliem's user avatar
1 vote
0 answers
1k views

I2C Hangs (sometimes) when Wire->endTransmission() is called

Architecture MKRZero BME280 Atmospheric Sensor SSD1306 128x64 OLED Screen SparkFun GPS: device: https://www.sparkfun.com/products/14414 arduino library: https://github.com/sparkfun/...
T. Brian Jones's user avatar
0 votes
3 answers
2k views

Digispark Attiny85 draws more power for digital input than expected

I'm trying to figure out why my attiny85 (on a digistump developer board) draws around 3mA at 3V when setting up a pin as INPUT and connecting it straight to ground. The current is measured with a ...
schneida's user avatar
  • 111
0 votes
3 answers
2k views

Does a pulldown resistor use less battery power than a pullup resistor?

I am designing a circuit connected to a simple open-close sensor, like a switch. For ease of construction, the circuit with the sensor switch closes to ground, and uses a 1 MΩ pullup resistor to Vcc ...
dotancohen's user avatar
1 vote
3 answers
6k views

External vs internal pullup

There are two ways of pulling the pins in Arduino – using internal and external resistor. I wonder when I should use external resistor instead of INPUT_PULLUP.
zhekaus's user avatar
  • 439
1 vote
2 answers
4k 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-...
Tom Hale's user avatar
  • 431
0 votes
1 answer
232 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 ...
Tom Hale's user avatar
  • 431
1 vote
3 answers
10k 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 ...
4u53r's user avatar
  • 113
0 votes
3 answers
4k 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 ...
Nima Sajedi's user avatar
2 votes
2 answers
7k 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); ...
Magnus's user avatar
  • 157
2 votes
1 answer
256 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 ...
Cerin's user avatar
  • 1,658
-2 votes
1 answer
5k 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 ...
Mario J.'s user avatar
0 votes
1 answer
3k 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 ...
mheavers's user avatar
  • 237
2 votes
2 answers
6k 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: ...
Kono's user avatar
  • 21
0 votes
2 answers
966 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&...
juliussin's user avatar
  • 121
9 votes
1 answer
20k 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 ...
JFetz2191's user avatar
  • 155
0 votes
1 answer
78 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....
Gundesalf's user avatar
1 vote
1 answer
1k 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 ...
T. Peppers's user avatar
1 vote
3 answers
5k 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 ...
ewizard's user avatar
  • 173
0 votes
1 answer
537 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 ...
mkpappu's user avatar
  • 103
1 vote
1 answer
776 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 ...
BillyBag2's user avatar
  • 217
3 votes
2 answers
2k 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 ...
Maximilian Wiens's user avatar
0 votes
1 answer
2k 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 ...
Jasper's user avatar
  • 115
6 votes
1 answer
1k 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. ...
squarewav's user avatar
  • 191
0 votes
2 answers
158 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 ...
acpilot's user avatar
  • 653
0 votes
1 answer
2k 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 ...
DK2AX's user avatar
  • 85