How can I get an SPI ADC (MCP3002) on RPi2

Question

I would be happy if you give me a advice or show me the sample code.

One year before, I wrote a luminosity sensor application on my RPi model B in Ruby. Thanks to the this library I could make app without deep understanding.

https://github.com/jwhitehorn/pi_piper

I've got a RPi2 last week and I've tried to update my luminosity application. Unfortunately, pi_piper doesn't support RPi2. I'm thinking about using the WiringPi-Ruby instead of pi_piper but I don't have any idea where to start.

Here is the code and circuit that I made before.

require 'pi_piper'
loop do
  value = 0
  PiPiper::Spi.begin do |spi|
   raw = spi.write [0b01101000,0]
   value = ((raw[0]<<8) + raw[1]) & 0x03FF
  end
  puts value
  sleep(1)
end

I used the mcp3002 as a ADC.

Answer 1

If it must be in ruby, have you tried? https://github.com/joshnuss/bcm2835

However if you can give C a chance the WiringPi library has it built in see:
https://www.raspberrypi.org/forums/viewtopic.php?t=54366&p=470706

I'm using the MCP3008 and it works pretty much the same and if you do some digging around you can find the commandline debugger tools which come in handy :)