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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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 ...
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2answers
50 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 ...
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0answers
37 views

How is data being sent to this Dot Matrix LCD? Can I just read one of the pins on the board using SPI?

I'm good with programming but am getting better with electronics. Can you guys easily tell how data is being sent to my LCD? I think it's using SPI but am not sure. I built a music/video/network box ...
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0answers
65 views

Peripheral Board Power Issue

after having designed some custom PCBs, a main one with an ARM MCU and other peripheral boards.But there is one issue when peripheral boards are plugged into the main one. Please, let me introduce ...
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11 views

How To Switch On/Off A Circuit using GPIO [migrated]

I have a simple circuit that runs on 5 volts. Let's just say for simplicity that it is a circuit with an LED that lights up when a push button is pressed. The problem is that it has a push button ...
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1answer
28 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 ...
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3answers
91 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?
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1answer
86 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 ...
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1answer
59 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 ...
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1answer
68 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 ...
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2answers
58 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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2answers
148 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 ...
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2answers
104 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 ...
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1answer
130 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 ...
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1answer
40 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 ...
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2answers
84 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 ...
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0answers
50 views

HDMI sleep/wake detect

My goal is to trigger some events using a microcontroller when my monitor attached via HDMI goes to sleep and wakes up. The standard HDMI interface has 'Hot plug detect' on pin 19, which is pulled ...
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1answer
75 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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0answers
93 views

Reprogramming STM32 when using SWD pins as GPIO

I have prototyped a new design, but being short on pins I was forced to utilise the SWD pins as GPIO. I know when this is done it messes with the ability to program the chip as easily, giving the 'No ...
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2answers
100 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 ...
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1answer
50 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
46 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 ...
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0answers
45 views

Beagleboard Black all GPIOs are activated by a single GPIO

Earlier I was having a problem with BeagleBoard Black Rev C , which I discussed in the question below. GPIO.HIGH,LOW doesn't up LED Beagleboard I've found the real problem. Whenever I turn any ...
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0answers
69 views

GPIO.HIGH ,.LOW doesn't up LED Beagleboard

I am getting my hands on The Beaglebone Black Rev C. I have been trying to run the simplest possible program , turning on an LED. I've tried on the GPIO pins P8_3 and P8_5 , the python code is given ...
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1answer
58 views

reversed bias diode on GPIO

I was looking more into the GPIO pins of the ATmega328p and came across the simplified schematic of a I/O pin. The schematic includes two reversed biased diodes, one to the ground and one to the VCC. ...
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2answers
56 views

Reading data via GPIO

I have just learned GPIO and I've read a lot of in internet. As I understood GPIO port can be at one of two states: out and in. ...
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1answer
152 views

Pin value of a GPIO pin set as high impedance

I am using an STM32F4 discovery board and my intention is to set one of its GPIO pins at high impedance, which I have done as below: ...
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1answer
85 views

STM32 Timer Function Generator

I wonder how you can achieve that a GPIO pin accuratly toggles according to a certain pattern. This pattern is fully variable (no PWM) and is stored in memory. My conclusion of this is: The pin has ...
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3answers
149 views

Does this schematic with an old doorbell electromagnet look ok? And could it be improved?

I have a circuit which seems to work and I would just like someone to confirm that it looks ok and isn't going to damage a 3.3/5V system (Raspberry Pi). Also, if there are improvements / ...
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2answers
99 views

Question about this diagram [duplicate]

I am very much a software person and a rookie in electronics. I am trying to understand why do we need Diode D1 in the diagram explained in this post: ...
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2answers
84 views

Is there any compact relay (or any high current) chip for Raspberry PI?

I am fascinated how L293D makes it easy to control a DC motor. I wonder if there is any similar popular chip that controls a set of relays, so I don't have to use a bunch of transistors? PS. I am ...
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0answers
45 views

Beaglebone Black - Power sensors after boot

I am new to electronics and want to build a small thermometer/humidity sensor powered by a beaglebone black to get started on something practical. My issue is that the board doesn't start when the ...
1
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1answer
67 views

Will HD44780 display be hurt with 20mA on contrast pin? (pin 3)

I'm driving an LCD HD44780 display using my Raspberry Pi B+. Using a GPIO pin I'm managing the contrast adjustment (pin n. 3) on my LCD display with PWM. In the ...
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1answer
56 views

Using Breadboard Power Rails for i2c Bus

I'm working on a raspberry pi project that will use about a dozen i2c devices (mostly mcp23017s) and the wiring is getting a little crazy. Are there any downsides to routing SDA and SDL to one of the ...
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1answer
25 views

Power sensor 230 V

I would like to use a Raspberry PI to log when a heat pump is turning on and off. The pump is running on 230 V; what I need is a circuit that can detect changes in voltage level and translate that to ...
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1answer
49 views

Using bi-directional logic level shifter for SWD.

I have a SWD emulator running on a cypress FX3 board where two of its gpio pins emulates SWDCLK and SWDIO pins. The board runs at 1.8V. These pins have to be connected to target - spansion FM4 which ...
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2answers
69 views

Raspberry Pi GPIO using a relay switch [duplicate]

I want to use a relay switch with the GPIO on my raspberry pi 2 (40 pins). I found the link below on google and it mostly makes sense, what I'd like to know is why do I need to use a transistor to ...
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2answers
59 views

Safely connecting GPIO input to output

I'm working on piece of software for Raspberry Pi and I'm writing an integration test. One of the cases requires that I'm able to read a state of one pin on another (basically if one output pin is ...
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1answer
61 views

Creating a breakout panel for a Raspberry Pi GPIO lines

From the elinux.org documentation for this GPIO, I have summarized the following information: The Raspberry Pi Model A+ and B+ boards, and the Pi 2 Model B, have a 40-pin 2.54 mm header marked ...
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1answer
74 views

Driving an H-Bridge from one pin

I'm attempting to set up an H-Bridge that can be controlled from 1 GPIO pin of an Arduino. I tried setting up the following circuit with a lab power supply and noticed the following: When Vin was ...
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1answer
52 views

Use GPIO pin of PIC on a general way and also with a led

What should be the best way to connect a led on GPIO pin to work as an indicator but also as GPIO for use in other things. Should I connect it in a serial way? but I think Ill have a voltage divider, ...
2
votes
1answer
90 views

can't assign PORTD a variable value on PIC18F

I'm using the following code to test some GPIO while I mess around with the PIC18F45K20 demo board. I realised something was strange when I couldn't increment a value and see it reflected on the LEDs ...
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2answers
63 views

Isolating GPIO's using diodes

Schematic The arrows are GPIO's I want to be able to close multiple switches at once in any particular order in order to manipulate GPIO's manually. I could give each GPIO its own resistor, but when ...
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2answers
113 views

Using a high resistance pull down resistor

I'm trying to make a circuit where closing a switch will change a GPIO from low to high, and I want to minimize current as much as possible to increase battery life. The chip I will be using is Nordic ...
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1answer
198 views

IAR STM8 LED Pin On/Off Flash

i tried to flash the LED of this controller: http://www.cnx-software.com/2015/01/18/one-dollar-development-board/ (as you can see, there is a led connected to PD3) with this code: ...
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1answer
88 views

How to use CMSIS to set up bidirectional Port on STM32F4

I'd like to use the GPIO_TypeDef an GPIO_Init to create a bidirectional Port on the STM32F407, some input pins, some output pins. Do I just run GPIO_Init twice, once for the input pins and once for ...
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1answer
106 views

Can't control RB10 (and RB12) of the PIC32MZ2048ECG064 as a 'normal' GPIO [closed]

This is an excerpt from the datasheet of the PIC32MZ EC Family concerning peripheral pin select output mapping: I'm using the PIC32MZ2048ECG064. My question concerns RPB10. I would like to use RB10 ...
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1answer
65 views

sam3x8e gpio interrupt not working as expeced

I working on sam3x8e processor with atmel studio 6.2. I have configured two gpios for interrupt on falling edge as follows: ...
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1answer
199 views

Calculating resistor values for RPi circuit detecting AC current using H11AA1 and PNP transistor

I've got an electronic doorbell system (Aiphone IE-1AD) that sends a ~15Vac signal when the button is pushed. I used this blog post on detecting a signal on a similar door bell using a moteino ...
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0answers
83 views

Connecting encoders/SPI devices/LEDs/buttons to a Rasperry Pi

I'm trying to connect a model B rev 2 Raspberry Pi to a whole bunch of stuff to create a MIDI foot controller: Adafruit touch screen 20 switches (some foot, some encoder buttons) 8 x SPI LED drivers ...