{"id":949,"date":"2016-08-23T11:38:19","date_gmt":"2016-08-23T10:38:19","guid":{"rendered":"http:\/\/ofalcao.pt\/blog\/?p=949"},"modified":"2016-08-23T11:38:19","modified_gmt":"2016-08-23T10:38:19","slug":"lego-laser-harp-part-i","status":"publish","type":"post","link":"https:\/\/ofalcao.pt\/blog\/2016\/lego-laser-harp-part-i","title":{"rendered":"LEGO laser harp – part I"},"content":{"rendered":"
This post is part 1 of 2 of \u00a0LEGO Laser Harp<\/a><\/div>

This is an idea I’ve been postponing for several months but the time has finally come: an laser harp.<\/p>\n

After tinkering with lasers, fog, sound, color sensors and python I found myself wondering how to give a proper use to all that. Then I remembered Jean-Michel Jarre<\/a> and how his laser harp made such a big impression on me at late 80’s when I finally decided “hey, i wanna study Electronics!”<\/p>\n

<\/a>For a first version, let’s call it “a proof of concept”, I just want a simple 7-string harp that can play the basic 7 notes. Polyphony would be great but I doubt that the EV3 sound capabilities allow that (and I cannot afford the brute force solution of using 7 EV3 so that each one plays only a single note).<\/p>\n

So in the last months I’ve been buying EV3 color sensors and I finally have 7. Since the EV3 only has 4 input ports I need some kind of sensor multiplexer but thanks to mindsensors.com<\/a> I already have one EV3SensorMux<\/a> (and a second one is on the way, from an european distributor<\/a> – portuguese customs DO stink!)<\/p>\n

With 2 MUX it’s possible to connect up to 8 sensors to the EV3. Since I just want 7 “strings” I am considering using an 8th sensor to control the amplitude of the notes. I’ll try an ultrasonic sensor but I’m not sure if it has enough “wideness” to cover the whole harp, let’s see.<\/p>\n

So of course I’ll be using ev3dev<\/a> and python.<\/p>\n

Using the EV3SensorMux is easy: just plug it to an input port and ev3dev immediately recognizes it:<\/p>\n

lego-port port8: Registered 'in1:i2c80:mux1' on '3-0050'.\r\nlego-port port8: Added new device 'in1:i2c80:mux1:lego-ev3-color'\r\nlego-sensor sensor0: Registered 'ms-ev3-smux' on 'in1:i2c80'.\r\nlego-port port9: Registered 'in1:i2c81:mux2' on '3-0051'.\r\nlego-port port9: Added new device 'in1:i2c81:mux2:lego-ev3-color'\r\nlego-sensor sensor1: Registered 'ms-ev3-smux' on 'in1:i2c81'.\r\nlego-port port10: Registered 'in1:i2c82:mux3' on '3-0052'.\r\nlego-port port10: Added new device 'in1:i2c82:mux3:lego-ev3-color'\r\nlego-sensor sensor2: Registered 'ms-ev3-smux' on 'in1:i2c82'.\r\nlego-sensor sensor3: Registered 'lego-ev3-color' on 'in1:i2c80:mux1'.\r\nlego-sensor sensor4: Registered 'lego-ev3-color' on 'in1:i2c81:mux2'.\r\nlego-sensor sensor5: Registered 'lego-ev3-color' on 'in1:i2c82:mux3'.<\/pre>\n
Even better: by default all 3 mux ports are configured for the EV3 color sensor, just as I wanted!<\/p>\n
NOTE: as of today (kernel version ‘4.4.17-14-ev3dev-ev3’) my EV3 autodetection only works when booting with a non-default configuration:<\/p>\n
sudo nano \/etc\/default\/flash-kernel\r\n\r\n LINUX_KERNEL_CMDLINE=\"console=ttyS1,115200\"\r\n\r\nsudo flash-kernel\r\nsudo reboot<\/pre>\n
this was suggested to me by David Lechner in another issue<\/a>, hope will be fixed soon.<\/p>\n
To use the color sensors in python I just need to know their ports. With the MUX in port ‘in1’ and 6 color sensors connected, these are the ports to use:<\/p>\n
in1:i2c80:mux1\r\nin1:i2c80:mux2\r\nin1:i2c80:mux3\r\nin2\r\nin3\r\nin4<\/pre>\n
And to play a note in python I just need to know it’s frequency<\/a> to use with Sound.tone() function, so:<\/p>\n
C3 = [(130.81, TONE_LENGHT)] \r\nD3 = [(146.83, TONE_LENGHT)] \r\nE3 = [(164.81, TONE_LENGHT)] \r\nF3 = [(174.61, TONE_LENGHT)] \r\nG3 = [(196.00, TONE_LENGHT)] \r\nA3 = [(220.00, TONE_LENGHT)] \r\nB3 = [(246.94, TONE_LENGHT)]<\/pre>\n
And so this was the first script for my harp:<\/p>\n
#!\/usr\/bin\/env python\r\n\r\nfrom ev3dev.auto import *\r\n\r\nTONE_LENGHT = 150\r\n\r\nC4 = [(261.64, TONE_LENGHT)]\u00a0\u00a0 #Do4\r\nD4 = [(293.66, TONE_LENGHT)]\u00a0\u00a0 #Re4\r\nE4 = [(329.63, TONE_LENGHT)]\u00a0\u00a0 #Mi4\r\nF4 = [(349.23, TONE_LENGHT)]\u00a0\u00a0 #Fa4\r\nG4 = [(392.00, TONE_LENGHT)]\u00a0\u00a0 #Sol4\r\nA4 = [(440.00, TONE_LENGHT)]\u00a0\u00a0 #La4\r\nB4 = [(493.88, TONE_LENGHT)]\u00a0\u00a0 #Si4\r\n\r\nAMB_THRESHOLD = 9\r\n\r\nsensor1 = ColorSensor('in1:i2c80:mux1')\r\nsensor1.mode = 'COL-AMBIENT'\r\nsensor2 = ColorSensor('in1:i2c81:mux2')\r\nsensor2.mode = 'COL-AMBIENT'\r\nsensor3 = ColorSensor('in1:i2c82:mux3')\r\nsensor3.mode = 'COL-AMBIENT'\r\nsensor4 = ColorSensor('in2')\r\nsensor4.mode = 'COL-AMBIENT'\r\nsensor5 = ColorSensor('in3')\r\nsensor5.mode = 'COL-AMBIENT'\r\nsensor6 = ColorSensor('in4')\r\nsensor6.mode = 'COL-AMBIENT'\r\n\r\n# there is no sensor7 yet, I need another MUX\r\n\r\ns1 = 0\r\ns2 = 0\r\ns3 = 0\r\ns4 = 0\r\ns5 = 0\r\ns6 = 0\r\ns7 = 0\r\n\r\nwhile True:\r\n\u00a0\u00a0\u00a0 s1 = sensor1.value(0)\r\n\u00a0\u00a0\u00a0 s2 = sensor2.value(0)\r\n\u00a0\u00a0\u00a0 s3 = sensor3.value(0)\r\n\u00a0\u00a0\u00a0 s4 = sensor4.value(0)\r\n\u00a0\u00a0\u00a0 s5 = sensor5.value(0)\r\n\u00a0\u00a0\u00a0 s6 = sensor6.value(0)\r\n#\u00a0\u00a0\u00a0 s7 = sensor7.value(0)\r\n\u00a0 \r\n\u00a0\u00a0\u00a0 if s1 < AMB_THRESHOLD:\r\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Sound.tone(C4).wait()\r\n\u00a0\u00a0\u00a0 if s2 < AMB_THRESHOLD:\r\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Sound.tone(D4).wait()\r\n\u00a0\u00a0\u00a0 if s3 < AMB_THRESHOLD:\r\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Sound.tone(E4).wait()\r\n\u00a0\u00a0\u00a0 if s4 < AMB_THRESHOLD:\r\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Sound.tone(F4).wait()\r\n\u00a0\u00a0\u00a0 if s5 < AMB_THRESHOLD:\r\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Sound.tone(G4).wait()\r\n\u00a0\u00a0\u00a0 if s6 < AMB_THRESHOLD:\r\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Sound.tone(A4).wait()\r\n#\u00a0\u00a0\u00a0 if s7 < AMB_THRESHOLD:\r\n#\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Sound.tone(B4).wait()<\/pre>\n
So whenever the light level over one of the color sensor drops bellow AMB_THRESHOLD a note will play for TONE_LENGHT milliseconds.<\/p>\n
Unfortunately the sound is monophonic (just one note can be played at a time) and it doesn’t sound like an harp at all – it sounds more like my BASIC games on the ZX Spectrum in the 80’s.<\/p>\n
So I tried Sound.play(Wave File) instead. Found some harp samples, converted them to .wav files at 44100 Hz and it really sounds much better… but the length of the samples I found is to big so the “artist” have to wait for the note to stop playing before moving the hand to another “string”. Not good and also not polyphonic.<\/p>\n
Next post I’ll show a better approach for both quality and polyphony: MIDI.<\/p>\n","protected":false},"excerpt":{"rendered":"
This post is part 1  of 2 of \u00a0LEGO Laser Harp<\/a><\/div>
This is an idea I’ve been postponing for several months but the time has finally come: an laser harp. After tinkering with lasers, fog, sound, color sensors and python I found myself wondering how to give a proper use to all that. Then I remembered Jean-Michel Jarre and how his laser harp made such a … Continuar a ler “LEGO laser harp – part I”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","enabled":false},"version":2}},"categories":[13,157,154,18,158,19,20,148,98],"tags":[277,276],"series":[275],"class_list":["post-949","post","type-post","status-publish","format-standard","hentry","category-ev3dev","category-ev3dev-en","category-lego-en","category-lego","category-lego-mindstorms-en","category-lego-mindstorms","category-linux","category-linux-en","category-python","tag-laser-harp","tag-music","series-lego-laser-harp"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p2Mhyv-fj","_links":{"self":[{"href":"https:\/\/ofalcao.pt\/blog\/wp-json\/wp\/v2\/posts\/949","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ofalcao.pt\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ofalcao.pt\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ofalcao.pt\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ofalcao.pt\/blog\/wp-json\/wp\/v2\/comments?post=949"}],"version-history":[{"count":0,"href":"https:\/\/ofalcao.pt\/blog\/wp-json\/wp\/v2\/posts\/949\/revisions"}],"wp:attachment":[{"href":"https:\/\/ofalcao.pt\/blog\/wp-json\/wp\/v2\/media?parent=949"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ofalcao.pt\/blog\/wp-json\/wp\/v2\/categories?post=949"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ofalcao.pt\/blog\/wp-json\/wp\/v2\/tags?post=949"},{"taxonomy":"series","embeddable":true,"href":"https:\/\/ofalcao.pt\/blog\/wp-json\/wp\/v2\/series?post=949"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}