GPIO is an acronym for general purpose input/output. The term is typically applied to a pin on a microcontroller (or other device) that may be changed between an input and output under software control. It can be used for an application defined purpose, as opposed to being constrained to a single ...

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36 views

How can I close a remote controller switch with an optocoupler and a Pi?

I'm trying to close the contacts of a remote controller (wires are soldered to either side). I have an RPi and I'm yet to buy an optocoupler. What would I need to get this to work? A Pi outputs 3.3v ...
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2answers
36 views

How do I reduce the number of GPIO pins used for a CMOS camera?

I'm gonna make a cheap 360 camera with 5 of these OV7670 cameras but they use a whopping 18 GPIO pins each! (Btw, 18 X 5 = 90 Pins!) I'm using a C.H.I.P computer to control all this mess, but even ...
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votes
1answer
88 views

Humidity sensor DHT21 / AM2301 not measuring humidity in a Lamobo R1/Banana PI R1

I am trying to use a DHT21 with a Lamobo R1 aka Banana PI R1 to read temperature and humidity, with Armbian/Jessie and a 4.5.2 kernel. A Lamobo R1 is basically an A20 board raspberry pi compatible, ...
0
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1answer
47 views

STM32 F4 GPIO clock rate

I am looking at the STM32 F4 series Discovery board. I have the eval board on my desk currently. I want to use this system to send data from USB to a 3 byte parallel data bus using an external clock ...
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2answers
61 views

Safe push button hacking

Here is an object push button that needs to be hacked: simulate this circuit – Schematic created using CircuitLab Hacked object circuit is not accessible. From multimeter : button ...
3
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3answers
78 views

GPIO esd protection

I came across NXP app note highlighting esd protection for GPIO pins. I found two different schemes for digital IO and I2C as given below: As far as I know, I2C pins are same as Uni-directional ...
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0answers
18 views

Difference between external event mode versus external interrupt mode for stm32 [duplicate]

I am configuring GPIOs for stm32f0 MCU using CubeMX. I encountered this "GPIO mode" setting. It seems that GPIO mode can be triggered by "External event mode" or "External interrupt mode". See image ...
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1answer
70 views

Atmega328p: why button input is read as 0 when pressed?

I'd like to turn on the board's LED (PB5) when I press its button (PB7). ...
0
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0answers
32 views

BeagleBone GPIOs mode

I want to know what is the mode of BeagleBone white pin if I use it as an input, is it pull-up or pull-down or have both or what exactly, I am a little confused, I had read that it is pull-down and ...
2
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1answer
68 views

Confused between push-pull and open-drain

I am planning to use i2c based port expander (earlier I was using atmega328P's GPIO) for inputs and outputs. On a digikey search, I found MCP23008, MCP23009 and MCP23017 as possible replacements. Out ...
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1answer
46 views

What is slew rate control for an input GPIO?

I see a register where you can make the slew rate fast or slow for the GPIO. Does this matter when GPIO is configured as an input?
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0answers
37 views

Help to build Mini PCI-E add-on card for Raspberry Pi 2 [migrated]

Is it possible to build an add-on card that has mini PCI-E slot, SIM slot and LED and that can be attached to Raspberry Pi 2 GPIO header? It would save me one USB port and it would be more neater ...
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4answers
79 views

Working display connected by GPIO pins to microcontroller?

Would it be possible to add a normal HDMI port or a display to any microcontroller with the GPIO pins? (I didn't buy anything yet, I'm just getting information before I buy...) EDIT: Thanks for all ...
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0answers
37 views

ESP8266 using LOW-Level with GPIO0

as you know to put ESP8266 into bootmode GPIO0 should be connected to the ground. That works perfectly, but the problem I don't ...
0
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1answer
109 views

STM32F103 GPIO and wrong configurations

I have a few questions about gpio. First What if two push-pull pins with high level connected? My point of view is that there is no way for current and nothing bad will happen. And reading of pin ...
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1answer
137 views

Best way to control power with MCU gpio pin

This is my circuit. An MCU gpio pin should control the power of another IC. Because the component requires more current than the gpio pin can drive, an N-Channel MOSFET is used. This is IC has no ...
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0answers
24 views

Unable to upload lua code into the nodemcu

I am unable to upload lua code into the nodemcu, though AT commands work. I am following this instructable: VCC ----> 3.3V Power supply (Vout of LM1117) GND ----> Ground of power supply CH_PD ...
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1answer
19 views

What does short circuiting a RST front IO header do?

My motherboard has a connector to enable the use of a front panel RESET button: I would like to simulate the press of the button (equivalent to short circuiting the wires) by a Raspberry Pi, by ...
0
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1answer
72 views

Software SPI 3-wire read register

I currently try to read a register from an acceleration sensor (ADXL345). i try to simulate the SPI procedure with software. I wrote a readRegister function: ...
0
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1answer
44 views

Inconsistent GPIO values on Beaglebone Black running Debian

I'm trying to use GPIO on my Beaglebone Black, but I'm running into some behavior I don't understand. I have two pins (gpios 27 and 61) configured to input with ...
0
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1answer
36 views

can't figure out why dsPIC digital input is not working

Having trouble getting a basic digital input to work correctly. Just trying to use it as an additional condition for an LED flasher to work. Right now their example code works just fine but when I ...
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1answer
60 views

Problems reading GPIO states set between STM32F Discovery and Nucleo64 boards

I am currently having an issue setting up a communication protocol between an STM32F discovery board (using the latest HAL drivers) and a Nucleo64 board (using the same drivers). Essentially each ...
1
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1answer
91 views

How to use the Non Maskable Interrupt on SAM4S?

I'm trying to use the NMI on a SAM4S (Cortex M4), but I'm finding some hard time to make it work. The main objective is to jump to the NMI handler whenever the power is about to go down, so that I can ...
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2answers
92 views

Are most GPIOs on common MCU's merely 'sourcing' or also 'blocking'?

Granted most MCU's are configured such that to 'activate' a device on a logic high (take the simple case of an LED, or a relay or transistor for something higher power) the MCU is sourcing VCC and the ...
4
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2answers
74 views

NXP LPC GPIO Glitches on every power up. How to solve?

I've been using NXP LPC microcontrollers for some time. One problem that I've faced in several projects is that every time the MCU is powered and a GPIO is setup to LOW logic level and output, a ...
7
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3answers
754 views

What actually happens when we set direction on GPIOs in controllers ?

Generally, while working on GPIO pins of any controller/device, we set the directions for the GPIO pins. Let's say in LPC2148(ARM7 core) controller, we have IODIR to configure the direction of Pin. We ...
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0answers
28 views

How to set the limits of a Limiting Amplifier?

I want to use a limiting amplifier (LA) to prevent overdriving an input to a 3V3 GPIO, but I'm not sure how you go about setting those limits. I have an example of a 'typical circuit' which ...
0
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0answers
67 views

Interfacing Example for GT-511C3 Fingerprint Scanner and Raspberry PI 2 Model B

I want to know, how to connect GT-511C3 Fingerprint Scanner Hardware with Raspberry PI 2 Model B and will these connectors be good to achieve the same? and, I want to connect the scanner without ...
0
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0answers
16 views

photodiode recommendation for RPi 2B VLC [closed]

I'm going round in circles trying to find a suitable photodiode for my VLC project. I want to run it directly off my RPi 2B gpio and also feed into either a TIA or op amp to process a digital signal. ...
0
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0answers
22 views

understanding FPGA datasheet: access speed to io lines [duplicate]

I am looking for the right fpga chip for a project. Crucial is the speed at which the fpga can access the physical gpio lines of the chip in order to realize a parallel interface. As I could not find ...
0
votes
1answer
58 views

I2c between beaglebone black and STM32F4-discovery

I'm planning to connect my beaglebone black to stm32f4-discovery. The purpose is to test i2c library of beaglebone black written in c. But I'd like to check if I'd fry my boards. Would it be okay to ...
1
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3answers
96 views

What is the pin state during microcontroller flashing?

I know that upon reset most micros put pins into high-z state. Is this state preserved during microcontroller flashing? What precautions need to be taken if you are going to reprogram microcontroller ...
0
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2answers
42 views

Using Raspberry Pi GPIO for matrix switching

I'm working with a Raspberry Pi. I want to be able to connect any two of 7 pins together in a matrix fashion to control a device with a keypad input. This means I need to be able to short any of the 3 ...
0
votes
3answers
141 views

Wire microswitch so state can be read from Raspberry gpio

I'm trying to check whether a series of valves (described here Can I measure if current is on or off in cable with 24v DC (in a cheap way)) are open or not. Updated question to be more specific after ...
0
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2answers
62 views

Raspberry Pi: Do the electrons flow from the power pins or ground? [closed]

I'm rather new to this and am slightly confused about which direction the electrons actually flow. Using an LED with the knowledge that conventional current flows out of the cathode, and hence the ...
0
votes
1answer
30 views

Current drive capability

Can someone point out the mistake I'm making in reading this graph (which is from the ADI Blackfin 70x datasheet) If a driver was set high, to 1.8V, why would it be unable to source current? I'm ...
0
votes
3answers
124 views

What is the difference between Ground and Low?

What is the basic difference between sending a LOW signal vs GND to a circuit? What If I ground instead of sending LOW? Or similarly what is the difference between Vcc and HIGH?
0
votes
1answer
150 views

Output 48MHz system clock on a GPIO pin other than MCO pin on STM32F030

I want to output the max 48MHz clock signal of STM32F030 to drive another subcircuit. The problem is the chip STM32F030F4P6 (TSSOP-20 package) I prefer to use a GPIO because the MCU doesn't have the ...
1
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1answer
78 views

USB GPIO board stops responding after high voltage relay with load is switched on

I'm using Numato 16 GPIO board to switch relays on 8 Channel Relay Module. Until no 220V load is connected to the relay all works fine and I can switch on/off relay using Serial port command to GPIO ...
0
votes
1answer
203 views

SIM900 Power On/Off Circuit

I'm designing a board on which I'll connect a microcontroller with the SIM900 module. The recommended circuit for powering on the module (from the manufacturer datasheet) is given below. The module ...
1
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2answers
208 views

How can a GPIO logic to high amp/voltage logic adapter be built using multiple voltages? (5v, 12v, 24v)

I'm working on a project that requires making a fairly universal board (to work on different model machines). I need to hook up many pre existing motors and switches/sensors to the board that all ...
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votes
2answers
264 views

Modifying a thermostatic radiator valve for micro control

The photo below shows a electrical thermostat controller. The upper part is the motor with a gear. The motor has two wires attached. A red and a black one for the current. What this component does ...
0
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2answers
131 views

Transistor is always in saturated mode

I am new to electrical engineering so I am not even sure that I approach this problem correctly, so I will first give some background information. I have a RC car (LEGO dirt crusher 8369) that I want ...
1
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1answer
149 views

Microcontroller GPIO in audio circuits

I'm designing an analog synthesizer, which is controlled by an STM32 -microcontroller. In several parts of the circuit, I intend to use a GPIO pin to control switches in the circuit, and in two ...
0
votes
1answer
43 views

Minimum TTL 5.0V signal duration

I'm working on a little project in my physics lab. We would like to create a photon coincidence counter. We were thinking to use the Pi GPIO pin to monitor a couple of photo diode which produce a 15ns ...
1
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2answers
146 views

Driving a Sainsmart Relay using Raspberry Pi

I am actually a software engineer and not really familiar with wiring. I've been playing around with a Raspberry Pi Model B, and am looking to hook up a 2 PRONG Extension Cable to a Sainsmart 8 ...
0
votes
1answer
96 views

How to generate UART interrupt for GPIOs?

I am using PIC32 and I have few inputs. I want a UART Tx Interrupt to fire whenever any input becomes HIGH. I have somehow manged to write code for UART tx and rx ...
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2answers
126 views

Why won't my phototransistor interrupt my microcontroller?

I bought a couple of phototransistors. They all have one lead shorter than the other. I assume that, like normal diodes, this means that the longer lead goes to V+ and the short end goes to GND. I ...
1
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1answer
52 views

Error in making pins input in PIC32

I am trying to make some pins act as input in PIC32MX795F512L. I am doing like this ...
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1answer
66 views

FRDM K64-F GPIO Pins

I am building a small system to allow the FRDM K64-F to control some motors via a H-Bridge. My problem is I am sturggling to understand the documentation provided for the microcontroller. Can anyone ...