Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [floating-pin]

40 questions
21
votes
7 answers

Random number generators using a GPIO pin?

I just read through question AVR Random Number Generator and encountered a number of ways to generate random seeds in an AVR: Use a special-purpose "Secure AVR" Use an internal temperature sensor Read unwritten EEPROM Measure time intervals between…
Vorac
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2 answers

Arduino digitalRead reading wrong

I have set up my Arduino UNO with 4 input wires, they connect to the port 10, 11, 12, 13, they are connected to my breadboard with nothing on it but the wire. My code would simply…
Guilherme Garcia da Rosa
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2 answers

What to do with unused analog inputs?

I am working on an application using ATmega328p atmel microcontroller. I started with the 28 PDIP version, but now I want to use the 32 TQFP, which I noticed has 2 extra inputs after compiling my Altium project. These inputs are ADC7:6 which "serve…
esal26
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6
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2 answers

What's the benefit of not soldering NC pins compared to soldering them to a disconnected pad?

I've been looking at my scope's power supply board and I noticed that R7731A "Burst Triple Mode PWM Flyback Controller" in DIP has two NC pins which are not connected to absolutely anything. They've been inserted into holes, but there are no…
AndrejaKo
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6
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1 answer

What happens to GPIO pins that are not exposed in a (small) package?

In one of our projects, we use an STM32L071 MCU in an LQFP48 package. It exposes GPIO port pins PA0 to PA15, PB0 to PB15 and PC13 to PC15 on the pins of the package. The LQFP48 package doesn't expose GPIO port pins PC0 to PC12. But I can still…
NZD
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5
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Why do we connect unused (always low pins) pins to GND through a resistor instead of connecting it directly to GND?

I have been reading the datasheet of RV-3028-C7. Everytime it talks about a pin that might be unused in a certain scenario (should be logic low), it instructs to connect the pin to ground through a 10k resistor. Page 103:…
Mora
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5
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3 answers

Why does a pull down resistor eliminate floating input

Ever since I connected a button to an Arduino for the first time, I've wondered how does the resistor prevent floating input from happening? I've read several answers to similar questions, seen videos and read forum…
Magnar Kleppe
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1 answer

How can moving my foot possibly affect electronics meters away?

I'm curious about a strange effect I observed. I was designing a device, which sleeps most of the time and can be woken up by a loud sound signal, like an opening door, a clap, etc. The relevant part of the schematic: simulate this circuit –…
anrieff
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What should I do to unused input parts/features (analog and digital input pins, and power pins) of a video scaler chip?

I am working on a video scaler chip which has multiple inputs (i.e HDMI, DP, VGA) but I only want to use the VGA input. (Choosing another chip with only one input is not an option). The friendly datasheet did not mention any instruction on what to…
cheweyjunior
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What should I do with the unused Op-amp inputs?

I am building a simple inverting operational amplifier circuit where I am using a chip with dual amplifier. I am only using one of the two amplifiers. What should I do to the unused amplifier's input pins? Should I leave them floating or is there a…
dr3patel
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How does floating pin detection work?

On MCP34xx devices datasheet on page 2 it is written: The I2 C address bits for the MCP3427 and MCP3428 are selected by using two external I 2 C address selection pins (Adr0 and Adr1). The user can configure the device to one of eight available…
php_nub_qq
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3 answers

Microcontroller Unused pins Configuration

I am having this microcontroller - S32K142 64 pin 5V core voltage I have a few pins which I don't want to use. While checking the datasheet of the Microcontroller, I couldn't find any information regarding 'on what to do with the unused pins' So, I…
user220456
2
votes
1 answer

Floating Vdd; NV Pokemon saves

http://forums.benheck.com/viewtopic.php?f=18&t=38664 In the link, there is a thread discussing replacing gen 1&2 Pokemon cart sram ICs with fram equivalents. The only differences between old and new ICs (besides architecture) is the operating…
Alexander M
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Can a pull down be used to tie a line to ground?

From my recent introduction to pull-up/pull-down resistors, I understand that an input with a pull-down will stay low instead of floating. Since the pull-down resistor leads to ground, couldn't I also use a pulled-down pin as ground? My raspberry…
RocketLauncher
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How and why is "floating input" a valid state for RF/IR encoder IC's?

RF/IF encoder/decoder IC's such as this one, will accept the address-pin in one of 3 states: Floating High Low As per this excellent answer, I believe "Floating" input can assume either High or Low value due to variations in the EM field, if I…
bdutta74
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