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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58 views

Would driving transformer with MCU's GPIO cause durability issue?

For making isolated power supply, I would like to drive a transformer with two GPIO's of a MCU. The center tab of the primary will be connected to Vcc. And each end of the primary will be toggled ...
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4answers
93 views

How to drive LED when sinking current to MCU?

Hopefully a simple one. Should I always control by writing to the GPIO digital output? Or should I always leave it low and then tri-state the output? LED turns on when MCU pin sinks current: In ...
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2answers
94 views

How to create USB toggle switch controled by GPIO

I have Raspberry Pi setup as NAS. The storage is external HDD powered through USB. I would like to encase this whole thing in some nice box and still be able to easily use the HDD, without ...
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3answers
59 views

Understanding GPIO analog and digital

I'm trying to understand GPIO, and have read a bunch of different blog posts and I think I'm close to getting it, but still struggling with a few things. I've seen a few reference to GPIO only being ...
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3answers
138 views

Proper usage of a MOSFET to control USB

On the RaspberryPi.SE it was suggested that one can use MOSFET BS170 to switch a USB device on and off by a GPIO pin (3.3V). I need to get 500mA to power a GSM dongle; the voltage drop should ...
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1answer
87 views

Is it possible to get input from a 10x10 grid of switches using an arduino board? (Uno, Mega, etc.)

I'm more of a software guy but I'm working on a prototype of a game that will use a pressure sensitive 10 by 10 grid. This will require 100 switches just for the grid. The closest I've found to off ...
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3answers
125 views

Drawbacks of using single-ended communication over differential pairs

I recently bought a ZYBO FPGA board only to find out that there are exactly six regular single-ended GPIO lines wired to the FPGA. In contrast to that, 18 differential lines are available. The board's ...
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0answers
43 views

Xilinx Spartan3-E FPGA input impedance and input leakage current for the GPIO pins

I am trying to use one of SPARTAN3-E FPGA GPIO pin as an input to ADC. I want to know the input impedance and the leakage current for GPIO? Should I just connect my circuit's Vout to GPIO pin or ...
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1answer
37 views

Interfacing GPIO pins between a uC and RS-485 tranceiver

uC: EM357 datasheet RS-485 IC: sp3078e datasheet Two input pins on the sp3078e need to go high at the same time when I'm sending bytes. I'm using a single output pin on the EM357 to drive both of ...
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2answers
159 views

Cannot get a digital square wave on oscilloscope from the GPIO of the Raspberry Pi?

ENVIRONMENT: Running "Raspbian" on Model_B Raspberry Pi (Revision 2) w/ ribbon expanding the GPIO out onto a Breadboard as shown in the following image. SETUP Here is a close up of the GPIO ...
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2answers
769 views

Does driving an microcontroller's GPIO when it is powered off weaken the chip?

We are using the LTC5800-IPM microcontroller in a project. The way our design is now, the IC's GPIO pins will sometimes be driven high (to 3.3V) or low when it is powered-off. Will this weaken the ...
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3answers
124 views

Does a clamping current specification under Absolute Maximum Ratings imply that less current is OK?

I have an application where I want many small signal relays driven by an I/O expander chip. In this case, I have selected the Microchip MCP23017 (Datasheet) as an I2C to GPIO expander. I have also ...
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0answers
86 views

MSP430 GPIO behaviour on power off

I have a simple circuit which contains an MSP430 connected to a DAC8551. I'm using PORT1 so have implemented a bit-banging approach instead of using the USCI module (bad, I know). I've noticed a ...
2
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1answer
126 views

GPIO on PIC16F887 not working

I've set the PIC16f887 on both external crystal 20MHZ and internal oscillator 4MHZ, neither of them ever worked with the following code: ...
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1answer
59 views

Use voltage regulator instead of zener to protect GPIO

I've read several articles about protecting 3.3v GPIOs from unregulated over voltage, all of which involve using a zener diode, a diode for reverse protection and resistors in some fashion. example 1 ...
2
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1answer
78 views

Frequency Sensitivity of GPIO Pins

When reading from a GPIO pin, at what frequency do the crests and troughs of a wave begin to blend together to the point that the CPU can no longer distinguish between them? I assume the answer ...
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1answer
48 views

Reduce voltage to read buzzer with GPIO

Using the GPIO on a BBB I'm attempting to detect a change in voltage coming from a DC source that drives a buzzer when the machines cycle is complete. I've located the DC connections from the machines ...
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1answer
79 views

problems using atmega644pv jtag pins as gpio [closed]

I've been trying to use port C pins on an atmega644pv as gpio, and have been running into some trouble. as far as i can discern, it seems like the middle four pins (PORTC 2,3,4,5) are stuck in a high ...
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3answers
117 views

GPIO/PCIe programing

I want to connect a PCIe 16x 3.0 GPU card to a Raspberry pi. I don't mind lo loose bandwidth, i just want to use the core GPU capabilities. So, the only idea that came out to my mind is to use the 26 ...
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1answer
192 views

How to wire/interface a 4x3 membrane keypad

I followed this example to wire my keypad to my STM32F4 Discovery board. However any way I read data on the pins I keep getting same data which leads me to believe I wired something wrong. Here is ...
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2answers
163 views

internal circuitry of IO ports in MCU [closed]

Could anyone share the internal circuit(transistor level circuit) of GPIO section in a microcontroller? I am curious to see how a pin can serve as both input or output(of course only one at a time). ...
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1answer
76 views

Raspberry pi with direct relay

I have a very back to basics question. I've been using a 5v relay with the raspberry pi. The relay trigger is connected directly to an output pin and the other side is connected to the ground of the ...
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1answer
86 views

Is this circuit a viable implementation? [duplicate]

Following on from an earlier question where the implementation was flawed, can anyone advise if the below is a viable implementation of a circuit to handle a matrix keypad? The idea is that one ...
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1answer
88 views

2 logical inputs on the same circuit

Is the below a valid circuit implementation and are there any things to watch out for? It's a simplification of the larger circuit but the crux of it is that I need to sink current into two GPIO input ...
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2answers
229 views

Max switching frequency of GPIO pins of modern cheap FPGA

How can we estimate maximum switching frequency of GPIO FPGA pins? What is maximum data rate achievable when connecting two FPGAs together without using of integrated high-speed transceivers? Or when ...
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0answers
70 views

GPIO and light interrupter

I have a GPIO board on hand like this: I am a beginner to GPIO board and wish to seek some suggestions. I would like to connect a light interrupter / photointerrupter to one of the four inputs, but ...
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0answers
399 views

Digital Potentiometer (MCP4131) with Raspberry Pi

I'm very new in electronic stuff. I'm used to develop for desktop and mobile applications not for hardware products. I try to wire up my Raspberry Pi board with a MCP4131 Potentiometer. But it's not ...
2
votes
1answer
54 views

How to measure open-drain vs. hi-z with multimeter

I have an output pin configured to be either open-drain or hi-z. How can I use my multimeter to tell which mode it is in?
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1answer
144 views

Shift 0-1.8V logic to 0-5V logic

I'm using BeagleBoard-xM McSPI to drive an MCP42050 digital potentiometer. Before using the SPI chip itself I'll try bitbanging through 3 GPIOs (but my question relates to both configurations). BB ...
3
votes
1answer
115 views

When a pin needs to stay LOW or HIGH, is it okay to connect directly to VCC or GND?

For example, I'm using an Exar Exar SP3220EBCY-L RS-232 transceiver and the typical application loop back test shows that the EN pin is connected to GND and the SHDN pin is connected to VCC. Should I ...
3
votes
3answers
165 views

Increase GPIO outputs

I'm working on a project in which I need 32 outputs from an MCU that only has 8 free outputs. To accomplish my goal I have the following requirements: I must be able to toggle more than one output ...
4
votes
1answer
143 views

ATtiny45 pin change interrupt PB5?

On the ATTiny45 data sheets it states that PB5 can be used as a digital IO pin and I want to use it to trigger a pin change interrupt, my only issue is that it is also the reset pin and the moment I ...
2
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0answers
131 views

How to select gate and gate-source resistors and N-MOSFET for controlling a 5V load from 3.3V input?

I want to control a 5V valve from my BeagleBone Black. As a single GPIO port only has 3.3V with 8mA I cannot use common relays. I found this thread: how to use a 3v output to control a 5v relay ...
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1answer
51 views

How can I turn the power of an external circuit on and off? [closed]

I have a circuit of batteries which power some good old light bulbs. I now want to turn the light bulbs on and off through GPIO. Unfortunately I have no idea how this would look like. Which ...
3
votes
1answer
301 views

i2c over gpio - level shifter

I'm quite new to this. I have just basic background in electronics. So I would appreciate an advice from someone more experienced. I would like to connect an i2c display to my tp-link wr703n (ar9331) ...
2
votes
1answer
285 views

Simple circuit to boost line-level audio

I am looking for suggestions or pointers to a simple circuit that boosts line-level audio, so that it is strong enough to use with the ADC peripheral on my MCU. I am aware and have seen many that use ...
-1
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1answer
197 views

Use the same pin as digital output and analog input with an ARM (sam3x / Arduino Due)

I have an application where I need to use one pin as a digital output and analog input. I switch between input and output at a "high" frequency (>1 kHz) and it takes to much time to disable and enable ...
7
votes
2answers
277 views

What happens on the STM32 when two pins are configured to have the same alternate function?

Reading through the STM32F051 manual, it looks like it's possible to configure the same alternate function on two pins; for example, you could have multiple USART1_TX pins at the same time. Or for ...
7
votes
2answers
248 views

Is it safe to connect two MCU pins directly to each other?

I am working on an MSP430 project that requires me to route the output of one peripheral into the input of another peripheral. Thus, I have two MCU pins connected directly to each other. This looks ...
1
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3answers
529 views

Driving a high power (200mA) LED with a GPIO and NPN transistor

I'm trying to get my head around how to properly use NPN transistors to limit the needed current from my Raspberry PI GPIO. I want to drive a Luxeon Rebel LED from Phillips ...
3
votes
2answers
355 views

Driving 7 segment displays through Raspberry Pi's GPIO

So I was thinking of wiring up four 7-Segment displays through the Raspberry PI. I'd do that by multiplexing each of them, and came across this: ...
3
votes
1answer
128 views

What is the structure of a typical 5V-tolerant input?

How do 5V-tolerant inputs work on a (3.3V or lower) device?
2
votes
1answer
2k views

STM32 GPIO Configuration

I am trying to figure out some online resource to figure out how to configure the GPIO Registers on an STM32F4 Cortex M4 board. I only have examples for the Cortex M4 ...
2
votes
1answer
247 views

How to control PcDuino pins from Java?

When I had Raspberry Pi I used to control the GPIO (pins) from a Java application using the Pi4J library. Is there any library to control the GPIO (pins) on the PcDuino using the Java language?
3
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1answer
271 views

Beaglebone Black ROV Control Scheme

I am looking for some advice regarding my control setup for an ROV and how to make it as smooth as possible. Currently, I have two arcade style joysticks with standard micro switches inside. How I ...
1
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1answer
133 views

Raspberry Pi / Arduino Button GPIO pins

I got myself a little button to start playing around with. Attempting to hook it up to a Rpi. What I wanted to confirm was the purpose and pins for each wire. The button I got is ...
5
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1answer
135 views

Advice regarding Remotely Operated Vehicle (ROV) control scheme?

Please let me know if this question isn't specific enough, I'll be happy to clarify. I am looking at various options for a control scheme for my underwater robot. I am in school and it is my job to ...
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votes
1answer
86 views

LED control using GPIO [closed]

I am using an industrial camera that has GPIO ports which I would like to use for turning LED plate off and on. LED runs on 24 V and 350 mA (between 350 mA and 1500 mA but 350 mA would be optimal). ...
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2answers
352 views

Raspberry pi relay check from remote

I'll start saying that I'm almost noob on electronics, so that's why I'm here. I'm looking for a smart way to check the state of an RF relay module remotely. This is the relay module: The module ...
7
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4answers
1k views

shorting a remote control pushbutton with GPIO and a transistor

I'm trying to control my garage door remote with a GPIO pin from my Raspberry Pi. Instead of driving a relay, it would be much easier to just short the pushbutton on the remote. Is this how I ...