Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [io]

This isn't a useful tag since all chips have input and output ports. Avoid using it, please.

115 questions
21
votes
2 answers

What's an alternate pin function on a microcontroller?

I'd like to know what "Alternative Function" refers to in the context of the IO ports of a microcontroller. I don't need to know how to activate it when connecting to a peripherial, but I'd like to know what it exactly is and why we'd need it.
user929404
  • 401
  • 2
  • 5
  • 9
13
votes
5 answers

C++ classes for I/O pin abstraction

I am looking for C++ abstractions for hardware I/O points or pins. Things like in_pin, out_pin, inout_pin, maybe open_collector_pin, etc. I surely can come up with such a set of abstractions myself, so I am not looking for 'hey, you might do it…
Wouter van Ooijen
  • 48,407
  • 1
  • 63
  • 136
10
votes
5 answers

How can I read a tristate output with microcontroller?

I'd like to interface the STAT line of an MCP73831 lithium ion charge manager IC to a microcontroller to read the current charging status of it. The datasheet explains, in the section 5.2.1, that the STAT line is tristate output and have the…
RHaguiuda
  • 1,141
  • 1
  • 13
  • 24
9
votes
4 answers

What's the Opposite of a sensor?

I'm trying to write an electrical engineering paper about different I/O on mobile phones. The inputs, such as the camera, microphone, accelerometer, GPS, can be considered sensors. What's the equivalent word for the outputs, such as display,…
Rich
  • 247
  • 3
  • 6
9
votes
4 answers

How long between Arduino digital pin and IC?

My current project involves using 74HC595 shift registers to control an LED display, however the display could be up to 5 or so metres away from the Arduino board. The plan is to use some DB9/RS232 cables between a box with the Arduino, and an…
user1307
5
votes
5 answers

Device to power either a red LED or a green LED

I have a green LED and a red LED. I want a sort of switch to turn either the red LED or the green LED on. For example: When the switch is off, the red LED is on, but if the switch is on, the green LED is on.
forever
  • 149
  • 1
  • 4
5
votes
2 answers

IO port register whose address is software defined (x86)

I want to do something that I assume must be fairly common in digital logic/bus design. It’s for a new expansion card for an old 8088-based computer. This isn’t some kind of college homework project. I want to create an 8-bit R/W IO port register…
David00
  • 113
  • 7
5
votes
4 answers

Bidirectional Shift Register

I am designing a project that has around 50 or so outputs and around 20 or so inputs. I have designed a chainable breakout board for a standard '595 shift register for the outputs, and was planning on using a '165 or similar for the inputs. Because…
captncraig
  • 2,054
  • 3
  • 24
  • 45
5
votes
3 answers

Multiple switches, same function. Can they be wired in parallel to a single I/O pin?

I'm working on a Raspberry Pi project that requires 30 separate momentary switches to be hooked up to trigger the same function within the software. It's for an art project. I don't need to distinguish between different buttons - I just need to…
A Steinmetz
  • 53
  • 3
4
votes
2 answers

What is a "current load" on a 24 V input used for?

The MAX14821 (datasheet) is a 24 V IO device that features selectable current loads for use in actuators on the inputs. What would this be used for? It's not just to load a 24 V "high" signal coming from a PNP-logic output, i.e. pull the input down…
handle
  • 446
  • 4
  • 20
3
votes
3 answers

How do Shelly products detect button presses?

I've been playing with home automation for a while now (mostly Sonoff) and recently discovered Shelly.cloud. I'm fascinated by the fact that most of their relays use a mains connected switches to interact with external inputs (see image below) -…
Vino
  • 141
  • 6
3
votes
3 answers

Can SPI and I2C be implemented using GPIO pins?

Can SPI and I2C be implemented using digital GPIO pins? I.e. can the SDA and SCK pins of I2C and the MISO, MOSI, SCK, and SS pins of SPI be emulated by setting GPIO pins as input and output accordingly? For example in the case of an…
Jet Blue
  • 1,123
  • 1
  • 17
  • 27
3
votes
1 answer

IO pin for iCE40 Ultra

What is the maximum IO pin current (for regular pins, not for LED pins) for iCE40 Ultra FPGA?
Test
  • 51
  • 4
3
votes
2 answers

Can not keep pin LOW during FPGA configuration

I would like to have a control signal that stays low all the time and goes hi only when I tell it to. Initializing the pin in the entity does not seem to set the value to zero (xc6slx25-3ftg256): Entity myEntity IS PORT( -- clock and other IOs …
Nazar
  • 3,142
  • 4
  • 35
  • 62
3
votes
5 answers

Microcontrollers: What to do with unused non-IO pins?

There's plenty of information on what to do with unused IO-pins on a microcontroller. You can set them to a floating output, ground them, or pull them up to Vcc or down to ground. However I can't find any information on what to do with non-IO pins.…
paw
  • 157
  • 2
  • 10
1
2 3 4 5 6 7 8