Paso 3: El código
El código es prácticamente el mismo que el tutorial, los cambios necesarios fueron el camino que se abre el bus SPI y la función que lee y escribe en el chip.
Así que crear un archivo spi_test.py:
#!/usr/bin/python import spi import time import os # Open SPI bus status = spi.openSPI(speed=1000000) # Function to read SPI data from MCP3008 chip # Channel must be an integer 0-7 def ReadChannel(channel): adc = spi.transfer((1,(8+channel)<<4,0)) data = ((adc[1]&3) << 8) + adc[2] return data # Function to convert data to voltage level, # rounded to specified number of decimal places. def ConvertVolts(data,places): volts = (data * 3.3) / float(1023) volts = round(volts,places) return volts # Function to calculate temperature from # TMP36 data, rounded to specified # number of decimal places. def ConvertTemp(data,places): # ADC Value # (approx) Temp Volts # 0 -50 0.00 # 78 -25 0.25 # 155 0 0.50 # 233 25 0.75 # 310 50 1.00 # 465 100 1.50 # 775 200 2.50 # 1023 280 3.30 temp = ((data * 330)/float(1023))-50 temp = round(temp,places) return temp # 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 repeating loop time.sleep(delay) Para ejecutar escribe:
sudo python spi_test.py
Todo el crédito va a Matt @ spy frambuesa pi & Louis Thiery para la biblioteca de SPI-Py
