Raspberry Pi projects. Make a switch Control volume Measuring temperature Measuring light Output PWM Blink LEDs Remote- control car Installing VNC

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Egbert Elliott
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1 Raspberry Pi projects Make a switch Control volume Measuring temperature Measuring light Output PWM Blink LEDs Remote- control car Installing VNC

2 Raspberry Pi 的 GPIO 只能接收及送出數位的訊號, 類比訊號就要做轉換成數位訊號才能輸入其中一個選擇是 Arduino, 這是一個應用很廣的數位板 ( 大致能做的事如下表所示 ), 有很多的使用者類似的還有 Gertboard 及 piface, 而這兩個都是為 Raspberry Pi 設計的產品

3 TesLng gpio pins: $gpio mode 0 out $gpio write 0 1

4 More usages of Raspberry Pi Adopted from Using adafruit MCP+Gpio to control volume hsp:// hsps://projects.drogon.net/raspberry- pi/

8 Transistor 9014 as a switch E B C 0V Din +V GND

9 Using MCP3008 to control volume Parts: tripotenlal meter, mcp3008, speaker

10 Review of gpio pins:

11 MCP3008 : analog to digital converter Analog input MCP3008 pins 9~16 are : VDD VREF AGND CLK DOUT DIN CS/SHDN DGND GPIO pins 3.3V 3.3V GND #18 #23 #24 #25 GND A D

12 Ciruit layout

13 Python script for the volume control The script is fairly simple. Half of the code (the readadc funclon) is a funclon that will 'talk' to the MCP3008 chip using four digital pins to 'bit bang' the SPI interface (this is because not all Raspberry Pi's have the hardware SPI funclon) The MCP3008 is a 10- bit ADC. That means it will read a value from 0 to 1023 (2^^10 = 1024 values) where 0 is the same and 'ground' and '1023' is the same as '3.3 volts'. We don't convert the number to voltage although its easy to do that by mullplying the number by (3.3 / 1023).

14 We check to see if the pot was turned more than 5 counts - this keeps us from being too 'jisery' and resehng the volume too oien. The raw analog count number is then converted into a volume percentage of 0%- 100%. When the trimpot is turned up or down it will print the volume level to STDOUT and adjust the audio level of the playing file by telling the mixer to adjust the volume.

15 #!/usr/bin/env python import Lme import os import RPi.GPIO as GPIO GPIO.setmode(GPIO.BCM) DEBUG = 1 # read SPI data from MCP3008 chip, 8 possible adc's (0 thru 7) def readadc(adcnum, clockpin, mosipin, misopin, cspin): if ((adcnum > 7) or (adcnum < 0)): return - 1 GPIO.output(cspin, True)

16 commandout = adcnum commandout = 0x18 # start bit + single- ended bit commandout <<= 3 # we only need to send 5 bits here for i in range(5): if (commandout & 0x80): GPIO.output(mosipin, True) else: GPIO.output(mosipin, False) commandout <<= 1 GPIO.output(clockpin, True) GPIO.output(clockpin, False) adcout = 0 # read in one empty bit, one null bit and 10 ADC bits for i in range(12): GPIO.output(clockpin, True) GPIO.output(clockpin, False) adcout <<= 1 if (GPIO.input(misopin)): adcout = 0x1

17 GPIO.output(cspin, True) adcout >>= 1 # first bit is 'null' so drop it return adcout # change these as desired - they're the pins connected from the # SPI port on the ADC to the Cobbler SPICLK = 18 SPIMISO = 23 SPIMOSI = 24 SPICS = 25 # set up the SPI interface pins GPIO.setup(SPIMOSI, GPIO.OUT) GPIO.setup(SPIMISO, GPIO.IN) GPIO.setup(SPICLK, GPIO.OUT) GPIO.setup(SPICS, GPIO.OUT) # 10k trim pot connected to adc #0 potenlometer_adc = 0;

18 ast_read = 0 # this keeps track of the last potenoometer value tolerance = 5 # to keep from being jiqery we'll only change # volume when the pot has moved more than 5 'counts' while True: # we'll assume that the pot didn't move trim_pot_changed = False # read the analog pin trim_pot = readadc(potenlometer_adc, SPICLK, SPIMOSI, SPIMISO, SPICS) # how much has it changed since the last read? pot_adjust = abs(trim_pot - last_read) if DEBUG: print "trim_pot:", trim_pot print "pot_adjust:", pot_adjust print "last_read", last_read if ( pot_adjust > tolerance ): trim_pot_changed = True

19 if ( pot_adjust > tolerance ): trim_pot_changed = True if DEBUG: print "trim_pot_changed", trim_pot_changed if ( trim_pot_changed ): set_volume = trim_pot / # convert 10bit adc0 (0-1024) trim pot read into volume level set_volume = round(set_volume) # round out decimal value set_volume = int(set_volume) # cast volume as integer print 'Volume = {volume}%'.format(volume = set_volume) set_vol_cmd = 'sudo amixer cset numid=1 - - {volume}% > /dev/null'.format(volume = set_volume) os.system(set_vol_cmd) # set volume if DEBUG: print "set_volume", set_volume print "tri_pot_changed", set_volume # save the potenoometer reading for the next loop last_read = trim_pot # hang out and do nothing for a half second Lme.sleep(0.5)

20 Analogue Sensors On The Raspberry Parts: Raspberry Pi MCP channel ADC Light dependent resistor (LDR) TMP36 temperature sensor 10 Kohm resistor source from: Pi Using An MCP3008 hsp:// spy.co.uk/2013/10/analogue- sensors- on- the- raspberry- pi- using- an- mcp3008/

21 a photo of test circuit on a small piece of breadboard :

22 Python Scripts Codes Part- 1, read raw data from mcp3008 #!/usr/bin/python import spidev import Lme import os # Open SPI bus spi = spidev.spidev() spi.open(0,0) # FuncLon to read SPI data from MCP3008 chip # Channel must be an integer 0-7 def ReadChannel(channel): adc = spi.xfer2([1,(8+channel)<<4,0]) data = ((adc[1]&3) << 8) + adc[2] return data

23 Codes part- 2, convert data from mcp3008 to voltages # FuncLon to convert data to voltage level, # rounded to specified number of decimal places. def ConvertVolts(data,places): volts = (data * 3.3) / 1023 volts = round(volts,places) return volts

24 Code part- 3 coverts voltages to temperatures # FuncLon to calculate temperature from # TMP36 data, rounded to specified # number of decimal places. def ConvertTemp(data,places): # ADC Value # (approx) Temp Volts # # # # # # # # temp = ((data * 330)/1023)- 50 temp = round(temp,places) return temp

25 CollecLng, calculalng and print- out # Define sensor channels light_channel = 0 temp_channel = 1 # Define delay between readings delay = 5 while True: # Read the light sensor data light_level = ReadChannel(light_channel) light_volts = ConvertVolts(light_level,2) # Read the temperature sensor data temp_level = ReadChannel(temp_channel) temp_volts = ConvertVolts(temp_level,2) temp = ConvertTemp(temp_level,2) # Print out results print " " print("light: {} ({}V)".format(light_level,light_volts)) print("temp : {} ({}V) {} deg C".format(temp_level,temp_volts,temp)) # Wait before repealng loop Lme.sleep(delay)

26 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 <= To stop PWM: p.stop() Note that PWM will also stop if the instance variable 'p goes out of scope

27 An example to blink an LED once every two seconds import RPi.GPIO as GPIO GPIO.setmode(GPIO.BOARD) GPIO.setup(12, GPIO.OUT) p = GPIO.PWM(12, 0.5) p.start(1) input('press return to stop:') # use raw_input for Python 2 p.stop() GPIO.cleanup()

28 An example to brighten/dim an LED: import Lme 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) Lme.sleep(0.1) for dc in range(100, - 1, - 5): p.changedutycycle(dc) Lme.sleep(0.1) except KeyboardInterrupt: pass p.stop() GPIO.cleanup()

29 Remote- control car Parts: 2 server motor, Raspberry pi with Adafruit assembled cobbler breakout and cables, basery for motors,

30 Python program import RPi.GPIO as GPIO #from Lme import sleep #from raspirobotboard import * import pygame import sys from pygame.locals import * pygame.init() screen = pygame.display.set_mode((160,120)) pygame.display.set_caplon('rp') pygame.mouse.set_visible(0) GPIO.setmode(GPIO.BCM) GPIO.setup(25,GPIO.OUT) GPIO.setup(24,GPIO.OUT) p1 = GPIO.PWM(25,50) p2 = GPIO.PWM(24,50)

31 while True: for event in pygame.event.get(): if pygame.key.get_pressed()[k_up]: print('u') p1.start(1) p2.start(10) if pygame.key.get_pressed()[k_down]: print('d') p1.start(10) p2.start(1) if pygame.key.get_pressed()[k_right]: print('r') p1.start(6) p2.start(7.4) if pygame.key.get_pressed()[k_left]: print('l') p1.start(8) p2.start(7.4) if pygame.key.get_pressed()[k_s]: print('s') p1.start(7.1) p2.start(7.4) if pygame.key.get_pressed()[k_q]: print('q') p1.stop() p2.stop() GPIO.cleanup()

32 Server motor with power and signal conneclons D

33 Installing VNC on raspberry pi hsp://learn.adafruit.com/adafruit- raspberry- pi- lesson- 7- remote- control- with- vnc/ installing- vnc

J. La Favre Controlling Servos with Raspberry Pi November 27, 2017

J. La Favre Controlling Servos with Raspberry Pi November 27, 2017 In a previous lesson you learned how to control the GPIO pins of the Raspberry Pi by using the gpiozero library. In this lesson you will use the library named RPi.GPIO to write your programs. You will