View source for Linker kit Base Shield for Raspberry Pi B+/2B/3 with ADC Interface V3.1

== Introduction  ==
Based on 3.0 version, we add some interface and use MCP3008 in stead of MCP3004, 4-channel ADC update to 8-channel ADC

[[File:RPI BASE SHIELD V3.1-9.JPG|600px]]

[[File:RPI BASE SHIELD V3.1-8.JPG|600px]]


== Interface ==

1x UART connector （UART）

1x I2C connector （I2C）

12 x Digital connector （D1~D12）

4x analog connector （ADC1~ADC4）

== Usage  ==
Enable SPI:

MCP3008 use SPI interface for communication, so we need to start SPI kernel module. In the previous OS we need enable SPI in /etc/modprobe.d/raspi-blacklist.conf.
But now we can enable SPI at raspi-config, also include I2C.

$sudo raspi-config

Choose:8. Advanced Options

[[File:RPI BASE SHIELD V3.1 -1.jpg]]

Choose:A6 SPI, Enable SPI

[[File:RPI BASE SHIELD V3.1-2.jpg]]

[[File:RPI BASE SHIELD V3.1-3.jpg]]

[[File:RPI BASE SHIELD V3.1-4.jpg]]

Reboot Raspberry Pi, then input 

$lsmdo

We can find SPI is enabled

[[File:RPI BASE SHIELD V3.1-5.png]]


Next, we install libraries:

$Sudo apt-get update

$sudo apt-get install python-imaging python-imaging-tk python-pip python-dev git

$sudo pip install spidev

$sudo pip install wiringpi



Test Code（print 8 ADC channels value）:

import spidev
import time

Vref = 3.3 #ADC_Vref = Voltage Switch 3.3V / 5V

# A0 = 0, A1 = 1, A2 = 2, A3 =3 
adc0 = 0 
adc1 = 1 
adc2 = 2
adc3 = 3 
adc4 = 4 
adc5 = 5
adc6 = 6 
adc7 = 7 

spi = spidev.SpiDev()
spi.open(0,0)

def readadc(adcnum):
# read SPI data from MCP3008 chip, 8 possible adc's (0 thru 7)
    if adcnum > 7 or adcnum < 0:
        return -1
    r = spi.xfer2([1,(8+adcnum)<<4,0])
    adcout = ((r[1] &3) <<8)+r[2]
    return adcout

while True:
	value = readadc(adc0) 
	volts = (value * Vref) / 1024		
	print("ADC%ld = %5.3f V" % (adc0,volts) )

	value = readadc(adc1) 
	volts = (value * Vref) / 1024
	print("ADC%ld = %5.3f V"% (adc1,volts) )

	value = readadc(adc2) 
	volts = (value * Vref) / 1024		
	print("ADC%ld = %5.3f V" % (adc2,volts) )

	value = readadc(adc3) 
	volts = (value * Vref) / 1024
	print("ADC%ld = %5.3f V"% (adc3,volts) )

	value = readadc(adc4) 
	volts = (value * Vref) / 1024		
	print("ADC%ld = %5.3f V" % (adc4,volts) )

	value = readadc(adc5) 
	volts = (value * Vref) / 1024
	print("ADC%ld = %5.3f V"% (adc5,volts) )

	value = readadc(adc6) 
	volts = (value * Vref) / 1024		
	print("ADC%ld = %5.3f V" % (adc6,volts) )

	value = readadc(adc7) 
	volts = (value * Vref) / 1024
	print("ADC%ld = %5.3f V"% (adc7,volts) )

	print("-------------------------")
	time.sleep(0.5)

[[File:RPI BASE SHIELD V3.1-7.jpg ]]