I need to poll for interrupts on a GPIO pin using python 2.7, and I wonder if there are any native functions or libraries to help me do that?
When searching for anything like this I find a lot about Raspberry Pi, but that is not what I need.
Is this doable?
It will be greate if you post what you already tried so we can help.
I did it like this
while 1:
events = po.poll(30000)
if not events:
print ('TIMEOUT!')
for fd, flag in events:
# check what's been done with os.lseek and os.read
This code is based on How do I wait for interrupts in different languages? question.
Whole code was done as a simple game for emebeded system on Raspberry PI and is available here
Related
have a USB module that accepts ASII commands to access functions. Need a way to send and receive commands in ASCII to module. speed 9600 Baud 8 bit no parity. To see if the module is awake I can send a "ver" inquire which means what software version is the Module. It will answer "ver 1". the module is a NumatoLab USBGPIO8 but the same commands can be used on all of their modules. I asked the same question of Numato labs but did not get a clear answer. Basically, I would like to print to the USB port and receive an answer. Thank you so much, Ray
I am looking for a way to read the USB-MIDI input live and have triggers, that run when a certain note is played. For example it should run function x, when an "e" is being played. This is Python 3 based either on windows 10 machine or a raspberry pi.
All the information I found has been years to decades old with pygame, py-midi, pyportmidi. Is there any current library that supports this? Pygame seems to rely on polling causing a short delay, which is a problem for this scenario.
In MIDI-OX, the Monitor displays the notes being played in real-time, though I can't do anything useful with it from there, as I need the python triggers, or events.
I am using the instructions of https://pimylifeup.com/raspberry-pi-rfid-rc522/ to learn how to read my rfid-rc522.
I installed all the things needed, and cloned from git all the files. I connected accordingly and double checked the wire.
The code in Write.py is
#!/usr/bin/env python
import RPi.GPIO as GPIO
import SimpleMFRC522
reader = SimpleMFRC522.SimpleMFRC522()
try:
text = raw_input('New data:')
print("Now place your tag to write")
reader.write(text)
print("Written")
finally:
GPIO.cleanup()
When I run it- The result stops after "Now place your tag to write" and nothing happens when I place my tag. Any help please? What's wrong here? The module gives red light meaning it is connected. Is it really connected? How do I know? Please help.
Edit: My title and tags were wrong in this question due to already saved data. I edited. :)
It can be multiple reasons why your reader is not retrieving any data:
The RFID cards that you are providing to the reader are not supported by the ISO 14443: Mifare Classic, 4K. (Some DesFire, etc...) are the cards you want to try. Source: https://en.wikipedia.org/wiki/ISO/IEC_14443
The MFRC522 is not receiving enough input voltage. Try to increase from 3.3V to 4V. I have tried with 5V months and the reader is still running perfectly, but be cautious. The safe range in NXP is from 2.5V to 3.6V. Source: https://www.nxp.com/docs/en/data-sheet/MFRC522.pdf
The library you are using does not support IRQ (Interruption Request). This means the process of reading UIDs is high CPU consuming and low in performance. Try to use this popular library which supports interruptions: https://github.com/ondryaso/pi-rc522 . You will need to connect another wire from the IRQ pin in the MFRC522 to one GPIO pin in the Raspberry that is free and supports reading/writing operations.
Check if SPI interfaces are enable in Raspbian. Open a terminal and run:
ls -l /dev/spi
Lastly, it could be that your reader is broken. Some chinese versions do not work as they should do. Maybe you should buy another one and try more luck.
I suppose you have connected all cables in the correct way between the MFRC522 and the Raspberry Pi. Check that again.
I have a laptop with Linux Mint and 4.4.0-78-generic kernel.
Also, I have some LEDs there in the /sys/class/leds directory, and I can turn them on and off in the userspace by executing "echo 255 > brightness" in Bash.
However, I want to switch them in my kernel module. Let’s say, that this module will listen a UDP socket and switch LED based on incoming packet data.
I have googled and found kernel source files called "leds-base.c", "leds-class.c" which contains functions to control LEDs. However, this functions require "struct led_classdev" to be passed, and I don't know where do I should get it.
How can I set LED brightness using its name from /sys/class/leds directory in a kernel module?
PS. I have seen a similar question, but it's about keyboard LEDs only, the LED I want to control is not a keyboard one, and can not be controlled by code in question mentioned before.
Implement an led_trigger class and call
led_trigger_event(led, LED_FULL);
and friends in your driver. You can bind your trigger to any LED by
echo my-trigger-name > /sys/class/leds/.../trigger
I am trying to read data from multiple microphones in Linux (ubuntu 14.04). I have a specific constraint that the reading from microphones should be via polling(so no waiting until there is data, although the data comes in high frequency). I wanted to know if that is possible in Linux? Unfortunately audio capture is not the area of my expertise and I would like to know if the choice of using Alsa is a good one. To better understand the problem, here is a pseudo-code that I had in mind:
open_the_audio_device();
set_the_parameters_of_the_audio_device();
while (!done)
{
poll_result=poll_the_devices(); //other non-audio devices are also polled here preferably, something like using select on all different file descriptors of audio, video, socket, etc.
if(poll_success_for_audio_device)
receive_audio_from_the_device_that_has_data();
else
do_some_other_very_fast_stuff_and_start_loop_again();
}
close_the_device();
My questions are 2 fold:
Is Alsa a good choice for this?
Can it be done somehow with some library that gives me a file descriptor so that I can use it with select function? if so this is optimal because there are other non-audio devices also working with select.
Thank you for your attention.
To prevent the snd_pcm_read*() calls from blocking, enable non-blocking mode with snd_pcm_nonblock().
To get pollable file descriptors, call snd_pcm_poll_descriptors_count() and snd_pcm_poll_descriptors().
It is possible to have multiple descriptors because some plugins might implement notifications differently.
To translate the result of a poll() on those descriptors back into a POLLIN/POLLOUT value, call snd_pcm_poll_descriptors_revents().