先上連接圖。
MCP3208 在2013年一位日本大佬的代碼:
https://seinzumtode.hatenadiary.jp/entry/20130918/1379501130
針對MQ-X這類氣體模塊,用MQ-2去做實驗(這個模塊是可燃氣體,那個打火機就能看出程序裏的讀數變化)。所以MQ2的AO的小針就是對應MCP3208上面的CH0的。
最後 如果再修改的好一點的話,關於pot move的這類代碼其實在氣體模塊這裏是用不到的,然後volume的意義針對氣體模塊其實應該重新整理公式去換算。
import time
import os
import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
DEBUG = 1
# read SPI data from MCP3208 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)
GPIO.output(clockpin, False) # start clock low
GPIO.output(cspin, False) # bring CS low
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
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
# Above pin number seems not working. I modified the pin as below.
# See also: http://elinux.org/RPi_Low-level_peripherals
SPICLK = 11
SPIMISO = 9
SPIMOSI = 10
SPICS = 8
# 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
potentiometer_adc = 0;
last_read = 0 # this keeps track of the last potentiometer value
tolerance = 5 # to keep from being jittery 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(potentiometer_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
if DEBUG:
print "trim_pot_changed", trim_pot_changed
if ( trim_pot_changed ):
# convert 12bit adc0 (0-4096) trim pot read into 0-100 volume level
set_volume = trim_pot / (10.24 * 4)
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 potentiometer reading for the next loop
last_read = trim_pot
# hang out and do nothing for a half second
time.sleep(0.5)