jsontocsv.rb

require 'json'
require 'open-uri'

raw_json = open('http://api.smartcitizen.me/v0.0.1/ba997ab4b0e21eda08b3da4a7b60a628/646/posts.json?from_date=2014-02-06&to_date=2014-02-08').read
json = JSON.parse(raw_json)

File.open('posts.csv', 'w') do |file|

  # write first line
  file.puts json["device"]["posts"][0].keys.join(',')
  # loop through posts, write each line of data
  json["device"]["posts"].each do |post|
    file.puts post.values.join(',')
  end

end