A great starter hardware project using the Raspberry Pi is hooking up a simple tactile switch to the Raspberry GPIO and detecting button presses in Python. This guide will guide you through setting up the circuit with the Raspberry Pi and reading the state of the button in Python. Integrating the button with Python allows you endless possibilities of actions to execute on a button press. You could send a tweet or turn on a LED.
We connect one side of the switch to an input pin on the Raspberry Pi, in this case we use pin The other side of the switch we connect to 3. The resistor is used as a current limiting resistor to protect our input pin by limiting the amount of current that can flow.
The idea is that the input pin will be low 0V when the button is not pushed. When the button is pushed it will connect the pin to 3.
When you hook up the circuit you can use the following reference to diagram to find the correct pin numbers. With the circuit created we need to write the Python script that actually reads the state of the button and executes code based on the state. Our initial script will initialize the GPIO port and then continuously read the status of the pin until we exit the program.
First we import the GPIO library and then setup the library to use board numbering. This is important since we want our program to read a low state when the button is not pushed and a high state when the button is pushed.
With the port initialized we can write the code that continuously reads the port and outputs a message when the button is pressed.
We use the GPIO. This is because we are continuously reading the state of the button. To get around this issue we can use a GPIO event. We will talk through how to do this in the next section.
We want to rewrite our program to output a single message whenever the button is pressed rather than continuously outputting a message. To do this we need to use GPIO events. Such a function is called a callback function.
An event can be an input pin being low or high, but it could also be when the pin changes from low to high — called rising — or when the pin changes from high to low — called falling. In our case we want to detect when the button is being pressed, that is going from low to high also called the rising edge. Before we setup the event we must however first write the callback function to be executed when the event is detected. Notice how we provide the function name as the callback parameter such that the library knows which function to call when the event is triggered.
Finally we instruct python to wait for keyboard input and when someone presses enter cleanup the GPIO input library resources and finish the program. This guide showed you how to read the state of a push button switch using the Raspberry Pi and the Python programming language. For more tips and guides on using electronics with the Raspberry Pi checkout the electronics section and join our newsletter!
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For this project we will be using the a Raspberry Pi Read more…. This post will Read more…. The circuit looks as follows: The idea is that the input pin will be low 0V when the button is not pushed. Writing the Python program to read the GPIO pin With the circuit created we need to write the Python script that actually reads the state of the button and executes code based on the state.
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There is no electrical current on these wires at all. Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Asked 3 years, 9 months ago. Active 3 years, 9 months ago. Viewed times.
Using a push button with Raspberry Pi GPIO
For my radio I have a PTT wire which needs to be grounded on the ground wire to key up. Do I need a breakoutboard? Sonic Sonic 11 2 2 bronze badges. Active Oldest Votes. Basically No. There must be some "current" on the wires or it would not work. Milliways Milliways 41k 19 19 gold badges 67 67 silver badges bronze badges.
Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Featured on Meta. Community and Moderator guidelines for escalating issues via new response…. Feedback on Q2 Community Roadmap. Related 2. Hot Network Questions. Question feed.The idea being that dummy packets that are sent before the actual data are used to trigger the vox and we then hope that the radio goes into transmit just in time before the actual data is sent.
The preferred method is to key the radio using a dedicated PTT line. For automated operation such as Packet Radio and APRS where packets are sent at the control of the computer an alternative method is required. We can use this line to trigger the PTT of a radio. We can change the function of GPIO pins by changing the mapping for those pins.
Unfortunately the Raspbian software does not come with a program to easily modify the GPIO pin mapping. The default configuration of the linux image uses the built in serial port to dump kernel messages and as a way to log into your raspi.
We also need to stop the system to spin up a terminal on the serial port. Once the software is installed it is simply a matter of setting the GPIO mapping for the desired pins at boot-up of the system. Please note that many radios will have different pinouts so it is important to check the correct way of keying PTT before you try anything out.
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GPIO pin on the RPi to trigger PTT
Personal tools Log in.Serial port: If your computer has a serial port built in or if you connect a USB to serial port adapter, used this. You'll need either a simple PTT circuit to "couple" or "buffer" the connection.
Simple stuff. Parallel port Linux only : If your computer has a parallel port, use one the data pins off it to ground the PTT line. This get's a bit complicated but you can then also fully control the radio's frequency and many other radio settings as well.
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baofeng aprs ptt controller
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Briefly describe the problem required :. Upload screenshot of ad required :. I know the pin works using a simple c program connected to LED. I am running under the pi user which is the default user for the pi. I have tried setting ownership of the value file to svxlink, root, added svxlink to gpio group, nothing works.
What am I missing? Robert Grimes. Signup Now! I have run sudo svxlink but no help. From: Marius Petrescu [mailto:marius That helped eliminate the error. I just forgot about the case insensitivity. However, the pi doesn't respond with anything happening on the pin.
I have a simple led circuit and a program that monitor the pin. Neither show any activity when svxlink turns tx on or off. I know the circuit work as a simple c test program blinks the led and the monitor detects the action. I must be missing something. Is there some other config option I need to set? Thanks for the help in advance. It took a while, but I got it to work. The problem was that somehow I had put the direction file to contain in instead of out.
Changing that made everything work. From: Robert [mailto:robert Murphy's rule got applied.My original goal was to hook up a raspberry pi with a gps module in my car. Baofeng radios trigger the ptt by shorting the sleeves of the two audio connectors. I isolated the audio lines with two audio transformers and set up the pi to trigger the transistor with a GPIO pin.
The transistor would short the two sleeves triggering the ptt. I also added a volume control pot to the audio in line so I could crank the volume all the way up on the radio and set the incoming audio to a normal level. That way I never need to remember exactly where to set the radio volume, I can just crank it to full volume every time. I tested the circuit and it was triggering the ptt correctly, so I 3d printed an enclosure for it using an openscad model that I found online.
I connected everything together and tried it out. Next, I rebuilt the circuit with an amplifier in line with the pc audio out. I used a 2n buffering an LM that is powered directly from the raspberry pi. Now the audio is intelligible and I am being picked up on aprs. There is a problem though. Sometimes the ptt gets stuck on. I guess there will be another version in the future. Published in circuitsElectronics and Radio.
Any luck with the PTT lock? Oh well came to your post looking for a stable keying circuit for the UV5RA as I have tried 3 different ones that all work fine with my FT51r but not with the baofeng even when disconecting one of the grounds which seems is a requirement with these radios have been told no ground on the mic in on the radio is the way to make it work may sort your problem out?
Comments are closed, but trackbacks and pingbacks are open. My first attempt was basically this circuit. Published in circuitsElectronics and Radio Previous Post esr meter. Next Post circuit construction techniques.
Let us call the two functions Function 1 and Function 2, and they are doing similar things as briefly described below. I googled a bit and found the question is easier than I thought.
Actually I think what the OP needs is the simple program I already briefly described in the question. On the other hand, 5V Arduino Uno should have no problems, because they are designed to entertain 5V logical level signals. For Rpi the usual get around is to use a logical level converter to step down the ham radio trasnsceiver's possibly 5V signals to 3V3 signals which are now compatible with Rpi. You can google AdaFruit or SparkFun for their very good newbie friendly logical level converter tutorials.
The most important thing about the hobby of Amateur Radio is to enjoy learning new technologies, experimentation, meeting new friends, public service, and to leave the hobby better than when you entered. The digital ham started at the same humble beginning, CW over spark gap.
With the advent of faster computer processors and vocoder technology, analog voice moved into the digital age, both on the HF bands and on VHF and higher bands. Yaesu has enter the arena with their proprietary System Fusion.
Short for Carrier Operated Relay. This is going back to the early days of repeaters in which all the repeaters had tubes in them, and all circuit switching was done by relays.
Nowadays most of the repeaters are solid state, except for a few which have tubes in the final amplifier, so now we call it COS or "Channel Busy" or So you ask how does it work and what's the purpose, and where can I find this COS on a receiver? The function of the carrier operated switch is to tell the repeater controller, if the repeater has one, that the receiver squelch is open, and that there is a signal there.
If the controller is set up for Carrier Squelch CSQ it then turns on and off the repeater transmitter. If the repeater does not have a controller, the COS simply does the function of turning on and off the transmitter. On some receivers the COS uses a relay and that has a dry contact to ground, and you won't see a swinging voltage, a 5k or so pullup resistor connected 12 volts, makes the COS voltage swing. The squelch circuit rectifies the hissing noise, its the noise that we hear when the squelch is open and no signal is present on the fm receiver.
Sometimes this noise is amplified and is applied to diodes to converted to a dc voltage, some other times to a voltage doubler to get a greater level of swinging voltage. That voltage is compared to the squelch pot and if it's greater the squelch stays closed, if it's less the squelch opens. There's another way to get a COS voltage from a receiver, that is with a VOX circuit on the receiver audio output, it does not work properly on a repeater, if someone has a full quieting signal and there is a pause in the speech the VOX closes so I won't go in detail with it here.
The COS squelch circuit has been used in repeater receivers for years, long before the tone squelch came to be very popular. So it is usually recommended to use the "pure" GPIO pins without alternative functions, just to make very sure.