electronics

Updated examples for OrangePi GPIOs

As part of working through adding OrangePi support to Home Assistant, Alastair and I decided to change to a different GPIO library for OrangePi to avoid the requirement for Home Assistant to have access to /dev/mem. I just realised that I hadn't posted updated examples of how to do GPIO output with the new library. So here's a quick post about that. Assuming that we have an LED on GPIO PA7, which is pin 29, then the code to blink the LED would look like this with the new library: import OPi.GPIO as GPIO import time # Note that we use SUNXI mappings here because its way less confusing than # board mappsings. For example, these are all the same pin: # sunxi: PA7 (the label on the board) # board: 29 # gpio: 7 GPIO.setmode(GPIO.SUNXI) GPIO.setwarnings(False) GPIO.setup('PA7', GPIO.OUT) while True: GPIO.output('PA7', GPIO.HIGH) time.sleep(1) GPIO.output('PA7', GPIO.LOW) time.sleep(1) The most important thing there is the note about SUNXI pin mappings. I find the whole mapping scheme hugely confusing, unless you use SUNXI and then its all fine. So learn from my fail people! What about input? Well, that's not too bad either. Let's assume that you have a button in a…

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GPIO inputs on Raspberry Pi

Now that I have GPIO outputs working nicely for Home Assistant using either a Raspberry Pi or an Orange Pi, I want to get GPIO inputs working as well. Naively, that's pretty easy to do in python on the Raspberry Pi: import RPi.GPIO as GPIO import time GPIO.setmode(GPIO.BCM) GPIO.setwarnings(False) GPIO.setup(17, GPIO.IN, pull_up_down=GPIO.PUD_DOWN) while True: print('Reading...') if GPIO.input(17) == GPIO.HIGH: print('Pressed') else: print('Released') time.sleep(1) That code is of course horrid. Its horrid because its polling the state of the button, and its quite likely that I can sneak a button press in during one of those sleeps and it will never be noticed. Instead we can use edge detection callbacks to be informed of button presses as they happen: import RPi.GPIO as GPIO import time GPIO.setmode(GPIO.BCM) GPIO.setwarnings(False) GPIO.setup(17, GPIO.IN, pull_up_down=GPIO.PUD_DOWN) def event_callback(channel): print('Event detected: %s' % GPIO.input(17)) GPIO.add_event_detect(17, GPIO.BOTH, callback=event_callback, bouncetime=50) while True: time.sleep(1) This second program provides helpful output like this: pi@raspberrypi:~ $ python gpio_button_edge_detect.py Event detected: 1 Event detected: 0 Which is me pressing the button once (it go high when pressed, and then low again when released). This is of course with a button wired to GPIO17 with a current limiting resistor between the button and the 3.3v…

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Pull Requests for the LCA2019 Home Automation tutorial

A quick list of things I did for the LCA2019 Home Automation tutorial. Of course Alistair did a lot more, but I still want to track these. Add OrangePi GPIO support to Home Assistant (declined) Document OrangePi GPIO support in Home Assistant (declined) Add OrangePi Prime GPIO pinouts to OPi.GPIO (merged, and released) Expose pullup resistor constants in OPi.PGIO (merged, and released) A simple burn in script for the workshop boards (merged) Automated generation of dhcpd.conf for the workshop network (merged) Clarifications for the workshop prerequisites (merged) Not all pins on Orange Pi support edge detection Clarify where the GPIO header is on the LCA2019 shield

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Further adventures in Home Assistant OrangePi GPIO

Its funny how a single sentence can change your course. In the last post about this work, I said: We also need to run hass as root,  because OrangePi GPIO support requires access to /dev/mem for reasons I haven’t dug into just yet. That's turned out to be (reasonably) a pretty big sticking point upstream. Access to /dev/mem gives you a whole bunch of access to the machine that Home Assistant probably shouldn't have. Alastair went off spelunking because he's more patient than me and found yet another OrangePi GPIO library. I think we're up to three or four of these at the moment, but this is the first one we've found which supports the sysfs interface to GPIO pins. That's exciting because it removes our run-as-root requirement. Its unexciting in that the sysfs interface has been deprecated by the kernel, but will remain supported for a while. I think people would be within their rights to conclude that the state of GPIO libraries for OrangePi is a bit of a dumpster fire right now. Anyways, the point of this post is mostly to write down how to use the sysfs interface to GPIO pins so that I can remember it later,…

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Adventures in Home Assistant Raspberry Pi GPIO

Alastair D'Silva is running what looks to be a very well prepared home automation tutorial at LCA2019 based on Home Assistant. I offered to have a hack on the support for GPIO pins on OrangePi boards in Home Assistant because it sounded interesting for a vacation week. The only catch being that I'd never done anything with GPIO pins at all on either Raspberry Pi or Orange Pi. The first step seemed to be to get GPIO working at all on a Raspberry Pi (which is currently supported out of the box with Home Assistant). This online tutorial has a simple example of a circuit and the associated python code to blink a LED on a Raspberry Pi, so off I went to build that circuit. The circuit has a LED with a 330 ohm pull up resistor on GPIO pin 18 on the board. The sample python code on the page above just blinks that LED, which I used to make sure that the circuit as working as intended. To configure the GPIO pin as a switch in Home Assistant, I added the following to configuration.yaml (noting that the empty rpi_gpio entry isn't strictly required, but will be later): rpi_gpio: switch: -…

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