18
votes
Driving PWM output frequency
I finally got a complete(ish) understanding from the bcm2835.h driver header file, so thought I would post and answer my own question for others.
The relevant bits from the header:
PWM
The ...
- 361
12
votes
Control Hardware PWM frequency
According to this formula:
pwmFrequency in Hz = 19.2e6 Hz / pwmClock / pwmRange
We can set pwmClock=1920 and pwmRange=200 to get pwmFrequency=50Hz:
50 Hz = 19.2e6 Hz / 1920 / 200
I test it on ...
- 316
12
votes
Can I use the GPIO for pulse width modulation (PWM)?
Recent Pis have two hardware PWM channels. In addition hardware timed PWM pulses may be independently generated on all the GPIO connected to the 40 pin expansion header.
In practice this means there ...
- 66.3k
9
votes
Accepted
How to use pigpio to control a servo motor with a keyboard?
I'm not sure if anyone will write the code for you. It's too broad a question.
You need to acquire a basic understanding of Python programming first, otherwise you'll be forever asking questions.
...
- 66.3k
8
votes
Driving PWM output frequency
On recent Pis (those with the 40 pin expansion header and the compute module) GPIO 12/13/18/19 may be used to provide hardware PWM signals.
The PWM clock source does not need to be the 19.2MHz ...
- 66.3k
7
votes
Accepted
pigpio - set_PWM_dutycycle vs hardware_PWM
hardware_PWM >>> set_PWM_dutycycle >>> software PWM
where >>> is orders of magnitude better pulse stability.
hardware_PWM
rock solid pulses
large choice and range of frequencies
large number of ...
- 66.3k
5
votes
RPIO does not work on Python 3, only in Python 2.7
The library needs to be installed for Python 3. The two Python versions 2.7 and 3.x don't share packages (because most code written for Python 3 is not backward compatible.
To install the RPIO ...
- 34k
5
votes
Accepted
PWM Control on Raspberry PI
I doubt you'll need to use the PWM capability of gpio 18.
There are many ways to provide hardware timed PWM on the Pi on all the user gpios. They are all variations on a theme and use DMA transfers ...
- 66.3k
5
votes
Accepted
PWM stop respond after hundreds of start/stop
I am fairly sure it is a bug in the RPi.GPIO module.
Look through https://sourceforge.net/p/raspberry-gpio-python/tickets/
As a workaround I suggest you do not use the start() and stop() methods in ...
- 66.3k
4
votes
Can I control this ESC/Brushless Motor with a Raspberry Pi and/or Arduino
ESCs (Electronic Speed Controllers) are typically controlled just like you would control a hobby servo -- with a PWM signal. There are many guides to controlling a servo that should be applicable to ...
- 2,984
4
votes
Max number of RC motors controlled by Raspberry PI
Simple. The maximum number is 0 (zero). You will need at least a transistor or a relay to drive the DC motor, as the GPIO pins on the rPi do not provide enough power to drive the motor. You will also ...
- 4,993
4
votes
PWM Fan causes clicking sound
At a PWM frequency of a nominal 10 Hz I'm not surprised you can hear clicks. You will be switching the fan on and off 10 times a second.
Experiment with frequencies in the range 100 to 1000 Hz.
- 66.3k
4
votes
Accepted
pigpio PWM and ALSA
By default pigpio uses the PCM peripheral to time the DMA leaving the PWM peripheral free for standard audio.
Perhaps your ALSA device is using high quality audio. If that's the case you need to use ...
- 66.3k
4
votes
Output Accurate, Detailed PWM signal
The Pis with 40 pin expansion header (and the compute module) have two hardware PWM channels which you should be able to use with wiringPi.
That would give you control of two ESCs.
From the software ...
- 66.3k
4
votes
Accepted
PWM control of motors with PHP front end
Will I need to have a Python script
You do not need python, you just need something with a module that wraps one or more of the following C libraries:
pigpio
wiringPi
libbcm2835
All of which ...
- 55.6k
4
votes
Accepted
PWM conflicts with I2C?
PWM should not conflict with I2C.
Everything below presumes the (predominant) Broadcom pin numbering scheme, which does not correlate to the physical arrangement of the pins.
I've never used GPIO 4 ...
- 55.6k
4
votes
Controlling servo with Raspberry Pi but it doesn't stand still
You are using the wrong tool for the job.
Servos require accurately timed pulses. The RPi.GPIO module uses software timing which leads to all sorts of timing jitter, which leads to a twitching servo,...
- 66.3k
4
votes
Raspberry pi PWM stability
You need to use hardware timed pulses for servos.
Software timed pulses will lead to jitter and a shorter servo lifetime.
Try pigpio, servoblaster, RPIO.GPIO, or similar which use hardware timed ...
- 66.3k
4
votes
Android Things: How many PWM pins on Pi 3 Model B?
All Pi models have identical GPIO, even though the pinout varies between models. PWM can be assigned to different pins, but there are still only 2 channels. See http://www.panu.it/raspberry/ for ...
- 53.3k
4
votes
PWM on 5V GPIO pin
If you take a look at the spec sheet for that fan (the fan you linked is a 4-pin varient):
You'll see that the PWM signal pin must be 5V. Now why it works with 3.3V (GPIO voltage) is likely because ...
- 6,185
4
votes
What is the relationship between angle and servo motor duty cycle? How do I implement this?
Servos are controlled by pulse width, the pulse width determines the horn angle.
A typical servo responds to pulse widths in the range 1000 to 2000 µs.
A pulse width of 1500 µs moves the servo to ...
- 66.3k
4
votes
Accepted
Can unstable PWM timing be corrected?
pigpio supports DMA timed PWM on GPIO 0-31. This has restricted frequencies and resolution.
http://abyz.me.uk/rpi/pigpio/python.html#set_PWM_frequency
pigpio also drives hardware PWM on GPIO 12, 13, ...
- 66.3k
3
votes
Accepted
Controlling a servo and playing sounds
RPIO, like pigpio, servoblaster, piblaster, and possibly others, use DMA to time the servo pulses. In effect the pulses are hardware timed. In contrast to software PWM they suffer little if any ...
- 66.3k
3
votes
More Software PWM
pigpio provides DMA timed PWM on all 21 user gpios, from C, Python, or any language supporting sockets.
video of PWM for 16 LEDs.
What do you mean by precautions?
- 66.3k
3
votes
Accepted
How to control a Traxxas XL-5 ESC directly from the GPIO?
I have resolved this. Thanks varesa for the note. Your information is correct but there are 2 elements that I think miss in all of the documentation I've ever found on this.
1) The pi is not the ...
- 126
3
votes
PWM input in Raspberry Pi
I can do fairly accurate pulse width measurement using the piGpio C library:
http://abyz.me.uk/rpi/pigpio/index.html
This library enables you to install a callback function that will trigger on any ...
- 31
3
votes
How can I control an RC servo?
Knowledge of how to do things on the Pi has improved quite a lot in the years since this question was asked.
There are at least four ways of generating hardware timed PWM/Servo pulses on the Pi's ...
- 66.3k
3
votes
Lighting a LED slowly with GPIO
To achieve slow dimming or brightening of your LED you will require (as others have posted before) PWM.
Introduction to PWM
There are primarily two types of modulation software and hardware. There ...
3
votes
Accepted
Default duty cycle of hardware PWM using wiring-pi
Based on RyanO suggestion, I setup pi-gpio with the commands
cd /opt/
sudo mkdir piscope
cd piscope
sudo wget abyz.me.uk/rpi/pigpio/pigpio.zip
sudo unzip pigpio.zip
cd PIGPIO
sudo make
sudo make ...
- 192
3
votes
I'm looking for a serial input type "polychromatic" LED as an output for my raspberry pi. Does such a device exist?
All I've heard of is RGB LEDs which are a red, a green, and a blue LED in one package.
Using PWM you can give each colour 256 different intensities to make the RGB LED appear to be any colour you ...
- 66.3k
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