Raspberry PI. Описание возможностей GPIO презентация

Raspberry PI. Описание возможностей GPIO лекция 1

Raspberry PI 3

CSI камера

GPIO

I2C

I2C. Датчика давления, температуры и влажности BME280 производства Bosch Sensortec

UART

SPI

Аналоги Raspberry

Raspbian

raspberry-gpio-python Importing the module try: import RPi.GPIO as GPIO except RuntimeError: print("Error importing RPi.GPIO! This is probably because you need superuser privileges. You can achieve this by using 'sudo' to run your script") Pin numbering GPIO.setmode(GPIO.BOARD) mode = GPIO.getmode() # or GPIO.setmode(GPIO.BCM)

Channels Warnings GPIO.setwarnings(False) Setup up a channel GPIO.setup(channel, GPIO.IN) GPIO.setup(channel, GPIO.OUT) GPIO.setup(channel, GPIO.OUT, initial=GPIO.HIGH) chan_list = [11,12] # add as many channels as you want! # you can tuples instead i.e.: # chan_list = (11,12) GPIO.setup(chan_list, GPIO.OUT) Input To read the value of a GPIO pin: GPIO.input(channel) This will return either 0 / GPIO.LOW / False or 1 / GPIO.HIGH / True.

Cleanup GPIO.cleanup(channel) GPIO.cleanup( (channel1, channel2) ) GPIO.cleanup( [channel1, channel2] ) import atexit def cleanup(): GPIO.cleanup() print("Cleaning up!!") atexit.register(cleanup)

Inputs Pull up / Pull down resistors GPIO.setup(channel, GPIO.IN, pull_up_down=GPIO.PUD_UP) # or GPIO.setup(channel, GPIO.IN, pull_up_down=GPIO.PUD_DOWN) Снимок в определенный момент if GPIO.input(channel): print('Input was HIGH') else: print('Input was LOW') Или цикл: (this assumes that pressing the button changes the input from LOW to HIGH) while GPIO.input(channel) == GPIO.LOW: time.sleep(0.01) # wait 10 ms to give CPU chance to do other things

Inputs. Как опрашивать правильно? Interrupts and Edge detection! LOW -> HIGH = rising edge HIGH -> LOW = falling edge wait_for_edge() function GPIO.wait_for_edge(channel, GPIO.RISING) Блокировка программы!!! # wait for up to 5 seconds for a rising edge (timeout is in milliseconds) channel = GPIO.wait_for_edge(channel, GPIO_RISING, timeout=5000) if channel is None: print('Timeout occurred') else: print('Edge detected on channel', channel) event_detected() function GPIO.add_event_detect(channel, GPIO.RISING) # add rising edge detection on a channel do_something() if GPIO.event_detected(channel): print('Button pressed')

Threaded callbacks def my_callback(channel): print('This is a edge event callback function!') print('Edge detected on channel %s'%channel) print('This is run in a different thread to your main program') GPIO.add_event_detect(channel, GPIO.RISING, callback=my_callback) # add rising edge detection on a channel ...the rest of your program... def my_callback_one(channel): print('Callback one') def my_callback_two(channel): print('Callback two') GPIO.add_event_detect(channel, GPIO.RISING) GPIO.add_event_callback(channel, my_callback_one) GPIO.add_event_callback(channel, my_callback_two)

Switch debounce (шумоподавитель) You may notice that the callbacks are called more than once for each button press. This is as a result of what is known as 'switch bounce'. There are two ways of dealing with switch bounce: add a 0.1uF capacitor across your switch. software debouncing a combination of both To debounce using software, add the bouncetime= parameter to a function where you specify a callback function. Bouncetime should be specified in milliseconds. For example: # add rising edge detection on a channel, ignoring further edges for 200ms for switch bounce handling GPIO.add_event_detect(channel, GPIO.RISING, callback=my_callback, bouncetime=200) or GPIO.add_event_callback(channel, my_callback, bouncetime=200)

Пример, на input # coding: utf-8 import RPi.GPIO as GPIO import time, datetime import atexit import lab_work_3_telegram def cleanup(): GPIO.cleanup() print("Cleaning up!!") atexit.register(cleanup) GPIO.setmode(GPIO.BCM) GPIO.setwarnings(False) GPIO.setup(19,GPIO.IN) GPIO.setup(20,GPIO.IN) def mic_fc_04(channel): #power 3.3v if GPIO.event_detected(channel): print(str(datetime.datetime.now()),' Шум в помещении!')

GPIO Outputs 1. First set up RPi.GPIO import RPi.GPIO as GPIO GPIO.setmode(GPIO.BOARD) GPIO.setup(12, GPIO.OUT) 2. To set an output high: GPIO.output(12, GPIO.HIGH) # or GPIO.output(12, 1) # or GPIO.output(12, True) 3. To set an output low: GPIO.output(12, GPIO.LOW) # or GPIO.output(12, 0) # or GPIO.output(12, False)

PWM Широтно-импульсная модуляция (ШИМ, англ. pulse-width modulation (PWM)) — процесс управления мощностью, подводимой к нагрузке, путём изменения скважности импульсов, при постоянной частоте.

Using PWM in RPi.GPIO To create a PWM instance: p = GPIO.PWM(channel, frequency) To start PWM: p.start(dc) # where dc is the duty cycle (0.0 <= dc <= 100.0) To change the frequency: p.ChangeFrequency(freq) # where freq is the new frequency in Hz To change the duty cycle: p.ChangeDutyCycle(dc) # where 0.0 <= dc <= 100.0 To stop PWM: p.stop()

Using PWM in RPi.GPIO An example to brighten/dim an LED: import time import RPi.GPIO as GPIO GPIO.setmode(GPIO.BOARD) GPIO.setup(12, GPIO.OUT) p = GPIO.PWM(12, 50) # channel=12 frequency=50Hz p.start(0) try: while 1: for dc in range(0, 101, 5): p.ChangeDutyCycle(dc) time.sleep(0.1) for dc in range(100, -1, -5): p.ChangeDutyCycle(dc) time.sleep(0.1) except KeyboardInterrupt: pass p.stop() GPIO.cleanup()

Checking function of GPIO channels gpio_function(channel) Shows the function of a GPIO channel. For example: import RPi.GPIO as GPIO GPIO.setmode(GPIO.BOARD) func = GPIO.gpio_function(pin) will return a value from: GPIO.IN, GPIO.OUT, GPIO.SPI, GPIO.I2C, GPIO.HARD_PWM, GPIO.SERIAL, GPIO.UNKNOWN