Simple Python wrapper and demo

Dan L. · 6 Nov 2015, 10:14

Hi @gosch, I started off with this.

Basically connecting a GPIO pin to a 330ohm resister, then the resister to the LED (longer leg), then the LED to ground. For my example code though, I was using 6 LEDs with 6 resisters, with the ground pin of each chained together and linked to a single ground pin on my expansion dock.

I also set up a button using an Arduino guide I found here.

Dan L. · 6 Nov 2015, 10:21

Nice one @Romans-Bermans!

gosch · 6 Nov 2015, 20:32

@Romans-Bermans: thanks for the picture!
@Dan L.: thanks for the info & links!

Jamie Street · 6 Nov 2015, 21:40

Hey @Dan-L , finally got some components to play around with!

Although I'm getting the following error when trying to read the input of a button using your helper, fast-gpio read 8 works perfectly though, any ideas?

Traceback (most recent call last):
  File "script", line 19, in <module>
    button_input = helper.getPin(8)
  File "/root/first_script/gpiohelper.py", line 26, in getPin
    fd = open(self.pinDirectionPath.replace("$", str(pin)), 'w')
IOError: [Errno 13] Permission denied: '/sys/class/gpio/gpio8/direction'

Dan L. · 6 Nov 2015, 22:15

@Jamie-Street Know what? I have the same problem with pin 8. If you try a different pin does it work?

I also have trouble with pin 13, but it doesn't actually give errors, it just doesn't do anything.

Dan L. · 6 Nov 2015, 22:18

BTW You can test easily with the command line too.

echo out > /sys/class/gpio/gpio5/direction
echo 1 > /sys/class/gpio/gpio5/value

echo in > /sys/class/gpio/gpio6/direction
cat /sys/class/gpio/gpio6/value

Jamie Street · 7 Nov 2015, 00:16

Cheers for the heads up, upon inspection it looks like the direction file is missing for pin 8, pretty strange.. perhaps the helper should create the file if it doesn't already exist?

Dan L. · 7 Nov 2015, 05:32

@Jamie-Street The helper doesn't specifically create those files individually, it triggers the export functionality. I'd say it's a bug with the Omega firmware...

Lazar Demin · 8 Nov 2015, 01:04

@Dan-L @Romans-Bermans we're still working on the drivers for the Arduino Dock, its a little more complicated than we anticipated. Should be out soon tho!

As for pin 8, I'll be looking into that, we might have made it output only for some reason. I'll double check.

Simon Yakov · 22 Nov 2015, 21:19

Thanks for the clear example.

Is there a reason I can't access pins 15-17 (extension board RGB led)?
I can update the values using (b)ash fast-gpio commands

root@Omega1:~# ls /sys/class/gpio/
export gpio1 gpio13 gpio18 gpio23 gpio6 gpio8 unexport gpio0 gpio12 gpio14 gpio19 gpio26 gpio7 gpiochip0

Patrick Ryan · 27 Nov 2015, 20:34

@Dan-L. Thank you for sharing that implementation.

I used your implementation, then added support for pin 8 ( via fast-gpio ). I also set it up so it could run on my mac in a simulated way.

Here is a link to a video showing it all work.

https://www.youtube.com/watch?v=jDDq9D50wGo

Thanks gain

Steve Fister · 4 Dec 2015, 15:23

@Romans-Bermans So for the pushbutton, how is that wired? It's hard to tell from the photo. It looks like the green leg is connected to 2V and the black leg is connected to RST? Please confirm. Thanks!

Peter Peters · 9 Dec 2015, 19:09

@Steve-Fister Probably not. Reading the code the button is connected to pin 26, the other side probably is connected to +5V. Although this might work, it is good practice to also connect a resistor (like 10kOhm) between pin 26 and ground, to ensure pin 26 is at 0V when the button is NOT pushed.

Boken Lin · 10 Dec 2015, 02:23

@Peter-Peters Logic voltage on the Omega is 2.8V. So the other side should be connected to 2.8V.

Peter Peters · 10 Dec 2015, 09:39

Woops, my bad.., but in that case the picture also shows the wrong connection...

What do you actually mean by 'logic voltage'? Is that the level where a '1' is detected or
the max input voltage for digital inputs?

So which of other 3 possible pins is the right one then? 2V, 2.5V, or 3V?

Or maybe the Onion Omega has a similar 'internal pullup' construct like the Arduino? In that
case you just change the circuit such that the button pulls 'down'.

Boken Lin · 10 Dec 2015, 14:10

@Peter-Peters Well, other voltages should work as well. Anything over 1.5V should be recognized by the Omega as a 1. You should be using the 2.5V.

François Levaux · 30 Dec 2015, 06:59

@Boken-Lin posted GPIO8 is for on board LED:
https://community.onion.io/topic/360/0-0-5-b251-gpio8-vs-others/2

Lazar Demin · 6 Apr 2016, 17:06

An update from the Onion side of things: we recently released an OnionGpio python module that can be installed via opkg.

Check it out here: https://wiki.onion.io/Documentation/Libraries/GPIO-Library

srikrishna Acharya · 29 Jul 2016, 09:29

@Lazar-Demin , I want to use GPIO interrupt driven and I would love to see a python implementation. can you put some light on it.

Kit Bishop · 29 Jul 2016, 11:53

@srikrishna-Acharya In case it is of any use to you, GPIO interrupt handling is covered in the package that I produced that is available at https://github.com/KitBishop/Omega-GPIO-I2C-Arduino

While there is nothing specifically Python related, the gpioirq program that is part of this package (at https://github.com/KitBishop/Omega-GPIO-I2C-Arduino/tree/master/gpioirq) is capable of running any command on interrupt on any selected GPIO pin. This would include executing any suitable Python script on interrupt.