class Mcp3008Pi

To use this gem you will need the following:

a Raspberry Pi
an MCP3008 10-bit Analog-to-Digital Converter (ADC)
an analog sensor e.g. photocell

Public Class Methods

new(pin: 0, pins: [pin], clock: 18, dout: 23, din: 24, cs: 25) click to toggle source

# File lib/mcp3008pi.rb, line 16
def initialize(pin: 0, pins: [pin], clock: 18, dout: 23, din: 24, cs: 25)

  @adc_pins = pins

  a = [clock, dout, din, cs]
  unexport_all a
  
  @clock = PiPiper::Pin.new :pin => clock, :direction => :out
  @adc_out = PiPiper::Pin.new :pin => dout
  @adc_in = PiPiper::Pin.new :pin => din, :direction => :out
  @cs = PiPiper::Pin.new :pin => cs, :direction => :out
  
  at_exit do
    
    # to avoid "Device or resource busy @ fptr_finalize - /sys/class/gpio/export"
    # we unexport the pins we used
    
    unexport_all a
  end      

end

Public Instance Methods

read() click to toggle source

# File lib/mcp3008pi.rb, line 38
def read()
  
  a = @adc_pins.map {|pin| read_adc(pin, @clock, @adc_in, @adc_out, @cs) }
  return a.first if a.length == 1
  
  return a
end

Private Instance Methods

read_adc(adc_pin, clockpin, adc_in, adc_out, cspin) click to toggle source

# File lib/mcp3008pi.rb, line 48
def read_adc(adc_pin, clockpin, adc_in, adc_out, cspin)

  cspin.on
  clockpin.off
  cspin.off
  
  command_out = adc_pin
  command_out |= 0x18
  command_out <<= 3

  (0..4).each do
    adc_in.update_value((command_out & 0x80) > 0)
    command_out <<= 1
    clockpin.on
    clockpin.off
  end

  result = 0

  (0..11).each do
    clockpin.on
    clockpin.off
    result <<= 1
    adc_out.read
    if adc_out.on?
      result |= 0x1
    end
  end 

  cspin.on

  result >> 1
end

unexport_all(pins) click to toggle source

# File lib/mcp3008pi.rb, line 82
def unexport_all(pins)
  
  pins.each do |pin|
    
    next unless File.exists? '/sys/class/gpio/gpio' + pin.to_s

    File.write '/sys/class/gpio/unexport', pin

  end
  
end