I have a question about sampling frequency. What is the sampling frequency using this example , and explain how you found the result.
The ADC is mcp3008 the same as in the project bellow.
Im using the same code but for another project. Current meter.
The example is taken from : http://learn.adafruit.com/reading-a-ana ... -pi/script
Thansk alot, and sorry for my spelling im from Sweeden
Code: Select all
#!/usr/bin/env python import time 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 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) print("%s milivolt" % (trim_pot*5000/1024)) time.sleep(0.5)