22
votes
gpio library on windows while developing
If you are just looking to test the whole code and not worry about the actual pins (as windows machines don't have GPIO), then you can fake it.
First, in your main python source directory, create a ...
- 351
21
votes
Accepted
GPIO: Warning Channel already in use
This code helped me get rid of the warning (the "finally" part at the end):
import RPi.GPIO as GPIO
import time
GPIO.setmode(GPIO.BCM) # Broadcom pin-numbering scheme
GPIO.setup(6, GPIO.OUT) # ...
- 396
14
votes
Accepted
Where are the uarts on the raspberry pi 4?
The preliminary Pi4 datasheet shows there are 6 UARTs.
UART GPIO
0 14/15
1 14/15
2 0/1
3 4/5
4 8/9
5 12/13
Given that UART 0/1 are both connected to the same GPIO you can only use ...
- 70.5k
13
votes
Can we use other GPIO pins as I2C
The whole point of I2C is it is a bus. You can therefore connect multiple I2C devices to the same GPIO provided they have different I2C device addresses.
If the devices share an address which can't ...
- 70.5k
12
votes
Accepted
How fast can GPIO pins toggle?
There are some benchmarks from Henner Zeller's repository on GitHub which claimed that directly outputting data to the GPIO could achieve up to 65.8 MHz on a Raspberry Pi 3 (not B+, mind, but I ...
- 6,278
12
votes
gpiozero Button.when_pressed
It is possible to use parameters with callback functions. See e.g. Documentation for button.when_pressed
This can be set to a function which accepts no (mandatory) parameters,
or a Python ...
- 3,506
11
votes
How to correctly install the python RPi.GPIO library
Assuming you have pip, the python package index installer, which is installed on the latest versions of Raspbian by default
You can use:
sudo pip install RPi.GPIO for Python 2
and
sudo pip-3.2 ...
- 161
10
votes
Webserver & GPIO python script (No access to /dev/mem. Try running as root!)
You don't so much need root access as permission to access the gpio device. Raspbian has a user group 'gpio' to enable this. By default the 'pi' user is in the gpio group and can access GPIOs. If you ...
- 501
10
votes
Is there any built in LED connected with GPIO pin?
Yes, it is possible to control the built-in leds. Green LED is easier.
According to here, though it is probably Pi 3 specific, since it didn't work for my Pi 4:
In the terminal:
sudo echo 1 > ...
- 1,759
10
votes
Where are the uarts on the raspberry pi 4?
As Joan has stated only 1 of UART0/1 is accessible (UART0 /dev/ttyAMA0 is connected to Bluetooth on later model Pi).
There are additional UART on the Pi4.
Raspberry Pi4 UART is a more up to date ...
- 58.6k
9
votes
Accepted
Is there documentation for RPi.GPIO
The official documentation is http://sourceforge.net/p/raspberry-gpio-python/wiki/Examples/
It doesn't seem to have a traditional API style of documentation.
- 70.5k
9
votes
Debouncing buttons with RPi.GPIO -- too many events detected?
As @joan points out, the bouncetime parameter in RPi.GPIO does almost exactly the wrong thing: it means when your switch bounces, you'll get the very first event, but that may not actually be ...
- 656
9
votes
Accepted
Error installing RPi.GPIO in virtual environment
It looks like the latest release does not support Python 3.9 but the alpha releases do: https://www.piwheels.org/project/RPi.GPIO/
You can install the alpha version with:
pip install rpi-gpio --pre
- 2,441
8
votes
Accepted
Can you connect multiple GPIO pins, to one ground pin?
Setting aside the ill-phrased part of the question (connecting multiple GPIO pins (which to my knowledge are 3 volts), to one ground pin) - which indeed short circuits the GPIO pins if they are set to ...
- 15.8k
8
votes
I can't get three LED lights to turn off and on in an order
You need to set the pin as an output before you use it.
To do that add the following line:
GPIO.setup(red, GPIO.OUT)
below the matching lines for green and yellow:
GPIO.setup(yellow, GPIO.OUT) ...
- 34.6k
8
votes
Is there any built in LED connected with GPIO pin?
though it is probably Pi 3 specific, since it didn't work for my Pi 4
It works on the 4 as well, you just need to set the right trigger. The instructions that you provided are not applicable to the 4 ...
- 81
7
votes
Accepted
connecting common anode rgb led
Connect the common anode pin to 3.3 volt and each of the other pins to a GPIO (add a current limiting resistor between the LED and the GPIO pin. To Light one of the colors set the corresponding GPIO ...
- 34.6k
7
votes
RPi.GPIO not found in virtual environment
The problem is that you don't have the GPIO module installed in your virtual environment. To correct this, run the following from within your virtual environment:
for Python 2
pip install RPi.GPIO
...
- 34.6k
7
votes
Accepted
Is the gpio readall command compatible with RPi 4?
As far as I am aware it should work provided you download and install the latest version of wiringPi.
http://wiringpi.com/wiringpi-updated-to-2-52-for-the-raspberry-pi-4b/
cd /tmp
wget https://...
- 70.5k
7
votes
Accepted
RPi.GPIO Cleanup() only specific pins?
See RPi.GPIO documentation.
Cleanup
At the end any program, it is good practice to clean up any resources
you might have used. This is no different with RPi.GPIO. By returning
all channels you have ...
- 70.5k
7
votes
Install GPIO problem
You can't install RPi.GPIO on Windows. If you want to mock GPIO calls on a PC, try gpiozero which has a mock pin interface: https://gpiozero.readthedocs.io/en/stable/api_pins.html
- 2,441
6
votes
How to correctly install the python RPi.GPIO library
Another potential cause could be because the RPi.GPIO library has C bindings and therefore need to have python-dev installed in order to compile correctly when installing.
Make sure you've got the ...
- 161
6
votes
Accepted
I need to control 8 LED's but I can only control 3? [helpful pictures attached]
The problem is the breadboard (though some would call it a feature). The breadboard you have has split power rails (Marked by the red and blue lines on the edge of the board). If you look carefully ...
- 34.6k
6
votes
Accepted
Blink script gives me "name error 'BCM' is not defined"
It's GPIO.BCM you want. Dot rather than comma.
GPIO.setmode(GPIO.BCM)
- 359
6
votes
Accepted
Is there a GPIO current limit function available, and where is the documentation?
Yes. The definitive source for RPi hardware documentation is the Raspberry Pi Foundation. The Foundation updated their published documentation to include programmable GPIO current limits recently (Jan,...
- 21.1k
6
votes
How can Rpi SPI python read the MFRC522 RFID / NFC module?
Question
How can Rpi python read a SPI MFRC255 RFID/NFC tag?
Short Answer
Part 1 - Introduction to I2C and SPI NFC/RFID Chips and Modules
Part 2 - Setting up SPI MFRC522 Module
Part 3 - ...
- 4,645
5
votes
How to connect a graphic card to Raspberry pi?
Graphics cards are usually connected via PCI or PCI Express bus.
The Raspberry Pi has no such bus. It has a built-in graphics card, however.
It's fast enough to run Quake 3 :-)
Edit: Actually, there ...
- 584
5
votes
Accepted
How to connect a graphic card to Raspberry pi?
It's probably not exactly what the original question had in mind... but technically, it is possible to connect graphic cards to the Raspberry Pi using a bus it provides, namely USB.
However, it ...
- 15.8k
5
votes
How do I make a device tree overlay for just a single GPIO?
Either I'm blind, or the whole concept of device tree overlays is very badly documented. Here is what I've found:
Install prerequisites:
sudo apt-get update
sudo apt-get install raspi-gpio device-...
- 173
5
votes
GPIO 02 and 03 seem always high when used as an input (with pull down resistors attached)
GPIO 2 and 3 are special in that they have hard wired 1k8 pull-up resistors to 3V3 fitted on board. That's to allow their use as I2C bus 1 (I2C requires pull-ups for SDA/SCL for proper bus operation)....
- 70.5k
Only top scored, non community-wiki answers of a minimum length are eligible