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Raspbery Pi Analog Input with MCP3008
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#!/usr/bin/env python | |
import time | |
import datetime | |
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) | |
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 | |
# 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 | |
adc_pin = 0; | |
while True: | |
begin_time = datetime.datetime.now() | |
# read the analog pin | |
adc_value = readadc(adc_pin, SPICLK, SPIMOSI, SPIMISO, SPICS) | |
diff_time = datetime.datetime.now() - begin_time | |
# print adc read time in us and adc value | |
print "%8d: adc_value: %4d" % (diff_time.microseconds, adc_value) | |
time.sleep(0.1) |
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