Questions tagged [sysfs]

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Intermittent access errors when writing to GPIO using SYSFS and Ruby

I am using Ruby to drive output GPIO pins using the old SYSFS pseudo-filesystem interface, and am regularly encountering intermittent Errno::EACCES: Permission denied @ rb_sysopen errors. My user is a ...
  • 123
0 votes
0 answers
116 views

sysfs blocks gpio pins after one minute from restart

I am using Raspberry pi 4b with Linux raspberrypi 5.10.63-v7l+. I am writing simple userspace program for control one GPIO by ioctl() (in my case GPIO 13 for example). However program responses: ...
1 vote
2 answers
989 views

Using GPIO PWM with sysfs

I'm able to write to GPIO pins with sysfs with the standard commands like echo "1" > /sys/class/gpio/gpio6/value, but that only turns the pin on or off. I tried echo "0.5" > /...
  • 121
0 votes
1 answer
885 views

Ubuntu 19.10 64-bit on Raspberry PI 4: How to unlock 100 MGz as min cpu frequency?

Is there way to unlock min cpu frequency for Ubuntu 19.10 64-bit for raspberry pi? First, this linux does't have /boot/config.txt similar to raspbian or ubuntu 18.04 from berryboot Next, the ...
2 votes
0 answers
62 views

EasyDriver stepper motor through sysfs not moving

I'm trying to activate a stepper motor using easydriver from here https://www.schmalzhaus.com/EasyDriver/Examples/EasyDriverExamples.html using sysfs and C, but it doesn't move. I connected my ...
  • 121
2 votes
1 answer
589 views

Raspberry GPIO button sysfs

I am trying to connect a button to my raspberry pi 3 (model B). I want to do it via the sysfs approach. Here is a picture or my small circuit: It cannot be simpler: the black wire is connected to a ...
  • 151
1 vote
2 answers
3k views

Is there a way to use interrupt-driven GPIO input through the sysfs interface without a race condition?

I want to use the GPIO pins to wait for a button-press without using a CPU spin loop. My preferred way of using the GPIO pins is via the sysfs interface at /sys/class/gpio, but it seems to me that ...
  • 111
0 votes
2 answers
556 views

Interfaces besides sysfs for GPIO programing in C

I am writing GPIO functions in C using standard libraries that come with the raspberry pi, and do not require installing other libraries such as wiringpi. So I have been using stdlib.h and stdio.h, ...
  • 2,443
1 vote
1 answer
897 views

Overclocking - CPU Frequency Measurement Accuracy: vcgencmd vs cpuinfo_cur_freq

As a follow-up to this question: Raspberry Pi B+ Overclocking: Force Turbo not working I had trouble getting force turbo to work. I was using the command: sudo vcgencmd measure_clock arm to get the ...
2 votes
1 answer
265 views

Configure Alt GPIO using sysFS

I have a Model B Revision 1.0 + ECN0001 that I am making a program in C to read and control a HCTL-2022 Quadrature Decoder using the GPIOs by way of sysfs. It's working great, but now I would like to ...
  • 123
8 votes
1 answer
3k views

GPIO callbacks in any language

I know the linux kernel has a language agnostic GPIO interface through /sys/class/gpio which can be manipulated with echo, cat, etc. How can this be used to create event driven callbacks ...
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