I do this all the time. Ethernet (Cat5) cable is twisted pair, which provides you with cross-talk protection.
Note that the longest run I've used is about 36", so you may have to do testing to ensure you're not receiving interference at long distances if that's what you're wanting to do.
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 are USB graphics cards by DisplayLink, see http://plugable.com/2014/03/06/displaylink-usb-2-0-graphics-adapters-on-linux-2014-edition
I don't know if anyone ...
The short answer is yes.
The long answer is yes, but...
3.3VDC is enough to run a low speed fan provided its designed for 3.3VDC.
I wouldn't try anything larger than a 40mm fan like this one, and this is why: the larger the fan blades are, the more torque is required to turn them, in in turn requires more power.
When you only have 3.3 volts, it takes ...
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 the PWM peripheral to time the DMA leaving the PCM peripheral free for high quality audio.
To do that from C use gpioCfgClock.
Connect a relay or an NPN transistor to bridge the two sides of your switch and program the Pi to set the base of the transistor or relay to high for about half a second - as if a button were being pressed.
I originally flagged this as being, possibly seriously, Off-Topic but technically there is a further method that make it possible to connect a graphics card to the RPi and have the latter generate content that is displayed on the former. It is called, *inserts drum-roll*: "X11" and is what is involved when you run an X server on your PC Desktop (which has ...
As the code is written in your question, it is creating an unlimited number of callbacks. Eventually the system will fall over because of a lack of resources.
Also a pigpio callback receives a set number of parameters (being gpio, level, and tick). You can't pass the return value of a function call as a callback.
cb = ...
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 seems unlikely that it will be possible to get an improved performance over the embedded GPU. It is also noteworthy that there might be significant issues with such ...
It is a warning only and may safely be ignored.
The warning is telling you that another program told Linux it wanted to use that gpio. It's all to do with Linux "exporting" the gpio to be visible to a user, so an ordinary user can read and write the gpio. The external program should have "unexported" the gpio when it was finished.
The warning should not ...
Not enough rep to comment, so here's a very short answer.
If your MOSFET is too 'stiff', you can add a BJT driver, i.e. a bipolar transistor stage that will accept the GPIO input and will pilot the fet in the second stage with the required voltage.
See the answer to this question for a schematic:
The DS18B20 is a (Dallas) 1-wire bus temperature sensor. It uses one wire for control and data.
Early versions of Pi software only allowed for the 1-wire bus to be started on GPIO4. You are looking at old or incomplete tutorials.
Recent versions of Pi software allow the 1-wire bus to started on any spare GPIO. There is still the limit of just one bus ...
I would not recommend calling a transistor a relay. While they would do essentially the same thing in this particular case (switch an electrical signal) they're technically different with respect to how they are driven and what kind of signal they switch. I will assume to drive an LED here (joan's answer mentions that additional considerations might be ...
If GPIO X has been exported then the directory /sys/class/gpio/gpioX will exist.
E.g. if GPIO 4 has been exported
$ ls /sys/class/gpio
export gpio4 gpiochip0 gpiochip100 unexport
If it has been exported the directory will have the following entries.
$ ls /sys/class/gpio/gpio4
active_low device direction edge power subsystem uevent value
By default the wiringPi's gpio utility uses wiringPi numbering for the GPIO.
You seem to want to use physical pin numbers.
Pin 7 is Broadcom GPIO 4 (wiringPi number 7).
Pin 12 is Broadcom GPIO 18 (wiringPi number 1).
So choose a numbering scheme and use the correct identifier for the GPIO and option for the gpio utility.
The recent GPIO Zero release (1.4) includes several new chapters on remote GPIO:
Configuring Remote GPIO
Remote GPIO Recipes
I should add that this is achieved via Joan's excellent pigpio package, mentioned in the other answer (GPIO Zero is just configured to use pigpio as its pin driver instead of the current default of RPi.GPIO).
Given the card is a small 'phat' style card and you cannot solder, this will limit your options.
The simplest way would be to buy another Pi (every house needs more than one as they get lonely) and just use one for playing music and one for other things.
The other option that can possibly solve the issue (depending on what else you need to plug in) is the ...
That is how Python displays a bytearray.
If the character is a printable character it is shown as such (the '}') in your example. If the character is not printable it is displayed in escaped format, e.g. \xAB where A and B are hexadecimal digits.
For your example '\x01\xc2\x00\x00\x01\xcc\xed\x00}' the 9 returned bytes are
1 01 1
2 C2 194
I found the completed solution for your issue:
RPi.GPIO basics 3 – How to Exit GPIO programs cleanly, avoid warnings and protect your Pi
I see this is the best way to other answers.
Basically you have to call cleanup.
import RPi.GPIO as GPIO
# do stuff …
# … left blank for the reader to fill in …
# … then perform a clean exit: