some simple bitbang mcp3008 test code

Author: [email protected]

Diff for: Adafruit_MCP3008/mcp3008.py

@@ -0,0 +1,94 @@
+#!/usr/bin/env python
+
+# just some bitbang code for testing all 8 channels
+
+import RPi.GPIO as GPIO, time, os
+
+DEBUG = 1
+GPIO.setmode(GPIO.BCM)
+
+# this function is not used, its for future reference!
+def slowspiwrite(clockpin, datapin, byteout):
+	GPIO.setup(clockpin, GPIO.OUT)
+	GPIO.setup(datapin, GPIO.OUT)
+	for i in range(8):
+		if (byteout & 0x80):
+			GPIO.output(datapin, True)
+		else:
+			GPIO.output(datapin, False)
+		byteout <<= 1
+		GPIO.output(clockpin, True)
+		GPIO.output(clockpin, False)
+
+# this function is not used, its for future reference!
+def slowspiread(clockpin, datapin):
+	GPIO.setup(clockpin, GPIO.OUT)
+	GPIO.setup(datapin, GPIO.IN)
+	byteout = 0
+	for i in range(8):
+		GPIO.output(clockpin, False)
+		GPIO.output(clockpin, True)
+		byteout <<= 1
+		if (GPIO.input(datapin)):
+			byteout = byteout | 0x1
+	return byteout
+
+# 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 /= 2       # first bit is 'null' so drop it
+	return adcout
+	
+# change these as desired
+SPICLK = 18
+SPIMOSI = 17
+SPIMISO = 21
+SPICS = 22
+
+# 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)
+
+# Note that bitbanging SPI is incredibly slow on the Pi as its not
+# a RTOS - reading the ADC takes about 30 ms (~30 samples per second)
+# which is awful for a microcontroller but better-than-nothing for Linux
+
+print "| #0 \t #1 \t #2 \t #3 \t #4 \t #5 \t #6 \t #7\t|"
+print "-----------------------------------------------------------------"
+while True:
+	print "|",
+	for adcnum in range(8):
+		ret = readadc(adcnum, SPICLK, SPIMOSI, SPIMISO, SPICS)
+		print ret,"\t",
+	print "|"