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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8 views

rasberry pi two devices GPIO [migrated]

I want to use both a the PiTFT monitor (http://www.adafruit.com/products/1601) & Woldsfson Audio (http://www.element14.com/community/community/raspberry-pi/raspberry-pi-accessories/wolfson_pi) ...
0
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39 views

Spurious interrupts using switches on a Raspberry Pi

I have two switches connected to GPIO pins on a raspberry pi. One side of each switch is wired to +3.3v. The other side is connected to an input pin via a 330 Ohm resistor, and each input pin has a ...
1
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1answer
119 views

Two or more different regulators connected to one battery

I want to make batteries provide power to both a micro controller (Raspberry Pi) and a 4x4 LED matrix. A simple circuit diagram is shown below. (only one LED is drawn in the fig. But regard it as LEDs ...
0
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0answers
25 views

Parallel Write On External Clock on STM32

I am using 8 GPIO pins on an STM32F407 for a parallel write to an external device (FT232H). The parallel write is synchronous, ie. I have to synchronize my data to a clock provided. According to the ...
0
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3answers
124 views

How to wire 12 cameras to trigger simultaneously

In the documentation of a camera it says: "To activate a GPI trigger, momentarily short pin 2 to 1." But I have 12 cameras and I want to trigger 12 cameras at the same time, how should the ...
0
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1answer
22 views

Configure GPIO pin for infrared interface (IRTIM) of STM32F030x4/x6/x8

I have a problem for use infrared interface (IRTIM) of my MCU. When I saw in Reference manual I could find this: Now, when I search for find GPIOx_AFRx register, I cannot find this register in ...
0
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1answer
32 views

SX1509 Analog to Digital Converter?

I purchased this product: https://www.sparkfun.com/products/11502 I've wired it up to 5 membrane pressure sensors which provide variable resistance depending on the pressure exerted. However I'm not ...
0
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1answer
35 views

pwm or gpio for pled display on beagle bone? [closed]

Wondering which adafruit bbio library i should use. I know nothing. My sense is that GPIO will be simpler to communicate the display info to the screen. The screen is a 128x32 adafruit pled
5
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3answers
90 views

Dump Flash Memory through a single GPIO pin

I'm working with Infineon's XMC4500 Relax Kit and I'm trying to extract the firmware through a single GPIO pin. My very naive idea is to dump one bit at a time through the GPIO pin and somehow ...
0
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1answer
68 views

How does a stm32f chip set its GPIO speed? (hardware, not register setting)

The speed of GPIO of a stm32 chip is set by register of OSPEEDR. It shows: 00: Low speed 01: Medium speed 10: Fast speed (50MHz in library) 11: High speed (100MHz in library) My guess is ...
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0answers
37 views

Communications between ArduPilot Mega and BeagleBoneBlack

I am trying to send complex control commands from BeagleBoneBlack(BBB) to ArduPilot Mega(APM) 2.5, such as loitering and acquire GPS location. The documentation on APM is somewhat dated and vague. I ...
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1answer
122 views

Beaglebone Black GPIO pins not working

I plugged a simple LED circuit that I've tested elsewhere into the Sys_5V (pin p9_7) and GND (pin p9_1). Then I tried p9_23 GPIO and set it to digital high it didn't work either. Why also: Sys_5V ...
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0answers
75 views

GPIO in device tree

My board has 3 GPIOs, namely gpio0, gpio1 and gpio2. Each of them have 32 pins. They were ...
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2answers
78 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 ...
0
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4answers
134 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 ...
1
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2answers
271 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 ...
0
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3answers
134 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 ...
1
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3answers
294 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 ...
1
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1answer
113 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 ...
1
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3answers
206 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 ...
0
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0answers
80 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
47 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 ...
3
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2answers
289 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 ...
4
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2answers
867 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 ...
2
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3answers
153 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
109 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 ...
3
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1answer
256 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
85 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
83 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 ...
0
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1answer
60 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 ...
0
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1answer
112 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 ...
0
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4answers
165 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
345 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
230 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). ...
0
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1answer
94 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 ...
0
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1answer
91 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 ...
1
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1answer
93 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 ...
2
votes
2answers
510 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 ...
0
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0answers
74 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 ...
1
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1answer
654 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
77 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?
1
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2answers
179 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
153 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
188 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
208 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 ...
3
votes
1answer
174 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
61 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 ...
4
votes
1answer
399 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
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1answer
412 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 ...
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1answer
238 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 ...