{"id":145,"date":"2014-01-14T12:42:21","date_gmt":"2014-01-14T12:42:21","guid":{"rendered":"http:\/\/192.168.3.4\/?p=145"},"modified":"2018-01-09T06:48:22","modified_gmt":"2018-01-09T14:48:22","slug":"sound-the-early-wireless-communication-protocol","status":"publish","type":"post","link":"https:\/\/www.cloudacm.com\/?p=145","title":{"rendered":"Sound &#8211; The early wireless communication protocol"},"content":{"rendered":"<p>Air pressure, defined by the popular perception of the meaning is the amount of air in your car tires.\u00a0 A meteorologist would be inclined to refer to it as <a href=\"http:\/\/en.wikipedia.org\/wiki\/Atmospheric_pressure\">atmospheric pressure<\/a>, which is measured with a <a href=\"https:\/\/www.sparkfun.com\/products\/11824\">barometer<\/a>.\u00a0 However, the physicist might say that the air molecules are repelling each other at a static rate until an outside force acts on them.\u00a0 All of these groups are correct.<\/p>\n<p>In short, air is a soup of various molecules of gas, liquid, and solids, proportionally in that order.\u00a0 All molecules have electrical shells that attempt to maintain a neutral charge.\u00a0 If a charge is applied to a group of molecules, they immediately repel each other.\u00a0 This expansion creates a pressure that builds up against the surrounding molecules.\u00a0 The pressure wave traverses space, expanding and diminishing.<\/p>\n<p>That explanation is the basic principal behind the wind, flight, speech, sound, music, and concussion.<\/p>\n<p>Variations in the speed at which sound pressure changes has been categorized, here is a list of them:<\/p>\n<ul>\n<li><a href=\"http:\/\/en.wikipedia.org\/wiki\/Barometer\">barometric pressure<\/a> &#8211; ~ to .2hz, The measurement of changes in atmospheric pressure.<\/li>\n<li><a href=\"http:\/\/en.wikipedia.org\/wiki\/Infrasound\">infrasound <\/a>&#8211; .2hz to 35hz, sub audio sound<\/li>\n<li><a href=\"http:\/\/en.wikipedia.org\/wiki\/Audible_frequency\">audio frequency<\/a> &#8211; 20hz to 20khz, the audible range of human hearing<\/li>\n<li><a href=\"http:\/\/en.wikipedia.org\/wiki\/Ultrasound\">ultrasound<\/a> &#8211; 20khz to 200mhz, used for ranging, imaging, and processing.<\/li>\n<\/ul>\n<p>Variations in the <a href=\"http:\/\/en.wikipedia.org\/wiki\/Sound_pressure\">intensity<\/a> also change its characteristics.\u00a0 The <a href=\"http:\/\/en.wikipedia.org\/wiki\/Speed_of_sound\">standards for sound<\/a> are well documented, as the subject has been studied since recorded history.<\/p>\n<p>With all that out of the way, now I can put this phenomenon to use with micro controllers as a communication method.<\/p>\n<p>Early computers used <a href=\"http:\/\/en.wikipedia.org\/wiki\/Modem\">modems <\/a>to communicate.\u00a0 These were <a href=\"http:\/\/youtu.be\/AByemfK_qD4\">acoustic coupled<\/a> and this means they were wireless at distances shorter than 2cm.\u00a0 Eventually, the audio function was removed and the audio frequency was transferred directly to the telephone wiring for more reliability.\u00a0 This was from<a href=\"http:\/\/youtu.be\/MEWr1ikhHhg\"> the demand<\/a> for automation, since machines can operate more efficiently than a human dialing.<\/p>\n<p>However, the earliest electromechanical device to communicate wirelessly was the telegraph using <a href=\"http:\/\/en.wikipedia.org\/wiki\/Morse_code\">Morse Code<\/a>.\u00a0 This is still used today, however most of the functions are handled automaticlly.\u00a0 Still the method is proven and its usefulness demonstrated time and again.<br \/>\n<iframe loading=\"lazy\" src=\"\/\/www.youtube.com\/embed\/ESN0nFbv6eQ\" height=\"135\" width=\"240\" allowfullscreen=\"\" frameborder=\"0\"><\/iframe><\/p>\n<p>Back to the modem, since this addresses the inherent bandwidth limitation of Morse Code.\u00a0 The audio characteristics of Morse Code makes is prone to noise and interference.\u00a0 Several methods are available that use a variance of <a href=\"http:\/\/en.wikipedia.org\/wiki\/Frequency-shift_keying\">frequency shift keying<\/a>, such as <a href=\"http:\/\/en.wikipedia.org\/wiki\/Multiple_frequency-shift_keying\">MFSK<\/a>, <a href=\"http:\/\/en.wikipedia.org\/wiki\/Gaussian_frequency-shift_keying\">GFSK<\/a>, and <a href=\"http:\/\/en.wikipedia.org\/wiki\/Continuous_phase_modulation\">CPM<\/a> to name a few.\u00a0 This allowed modems to communicate at faster rates never attainable with Morse Code systems.<\/p>\n<p>The subject of using audio as a means for micro controller communication is vast, I&#8217;m sure I&#8217;ll be revisiting this subject later.\u00a0 In the meanwhile, <a href=\"http:\/\/cargocollective.com\/apppluswhat\/Desk-Research\">here is some more details<\/a> about various communication methods used with smart phones.\u00a0 Enjoy.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Air pressure, defined by the popular perception of the meaning is the amount of air in your car tires.\u00a0 A meteorologist would be inclined to refer to it as atmospheric pressure, which is measured with a barometer.\u00a0 However, the physicist might say that the air molecules are repelling each other at a static rate until an outside force acts on them.\u00a0 All of these groups are correct. In short, air is a soup of various molecules of gas, liquid, and&#8230;<\/p>\n<p class=\"read-more\"><a class=\"btn btn-default\" href=\"https:\/\/www.cloudacm.com\/?p=145\"> Read More<span class=\"screen-reader-text\">  Read More<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-145","post","type-post","status-publish","format-standard","hentry","category-rd"],"_links":{"self":[{"href":"https:\/\/www.cloudacm.com\/index.php?rest_route=\/wp\/v2\/posts\/145","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.cloudacm.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.cloudacm.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.cloudacm.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.cloudacm.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=145"}],"version-history":[{"count":8,"href":"https:\/\/www.cloudacm.com\/index.php?rest_route=\/wp\/v2\/posts\/145\/revisions"}],"predecessor-version":[{"id":1616,"href":"https:\/\/www.cloudacm.com\/index.php?rest_route=\/wp\/v2\/posts\/145\/revisions\/1616"}],"wp:attachment":[{"href":"https:\/\/www.cloudacm.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=145"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.cloudacm.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=145"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.cloudacm.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=145"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}