![\"CIMG9954\"](\"https:\/\/andyland.info\/wordpress\/wp-content\/uploads\/CIMG9954.jpg\")
<\/a><\/p>\nOn the left side there is a circuit consisting of an Arduino and an Attiny85. The Arduino creates a low-frequency ( ‘bass’ ) sine-shaped tone which perfectly sits in the frequency range of the mixer’s bass-EQ. I did some testing here to find the perfect frequency. Testing means: Using Ableton Live to create a white noise, feed this into the mixer, feed the mixer’s output back into Ableton and use the Spectrum-tool to see which frequency gets most influenced by the bass-EQ (C2, that is).<\/p>\n
Creating a somewhat true sine needs some effort since the Arduino’s analog outputs only do PWM which isn’t very useful when talking about low-frequency audio signals. PWM basically creates a square-wave signal with a certain pulse-pause relation. While this might be okay for dimming an LED, this becomes quite unusable when dealing with audio because you can simply hear that it’s no sine – the lower the frequency the more the signal turns into some sort of ‘click’-noise. No wonder, the bass-EQ doesn’t influence this to any convience.<\/p>\n
That’s why I used this<\/a> solution to make the Arduino spit out something that’s a little more sinewave-like. I ommitted the circuit as you may see on the picture below. I didn’t have the necessary parts lying around and it worked nevertheless.<\/p>\n The Attiny85 is used to create the second tone. It’s a simple PWM signal at 480 Hz. This time the PWM-nature of the signal can be used for our benefits: A square-wave signal has a recognizable amount of harmonics. You don’t hear one but (at least) two tones. Perfect for us because the mixer I used perfectly\u00a0influences (well … “perfectly” )\u00a0 the signals with its mid- and hi-EQs.<\/p>\n <\/p>\n The code for the Attiny85 looks like this:<\/p>\n void setup(){ void loop(){ void buzz(int targetPin, long frequency, long length) { I guess I found it over here<\/a> and adapted it to my needs.<\/p>\n the two microcontroller’s output signals are fed into a 7408 (Quad AND) and then sent out into the analog world by a circuit I found over at the MunichMakerLab.<\/a> This is my first audio-circuit with an Arduino. it’s probably spine-crawling for those who do this on a more professional base but I was getting the best results with this circuit.<\/p>\n [Edit] As someone pointed out in the comments section for this post on Hackaday<\/a> this might read\u00a0like I didn’t know at all what I am doing here or that it’s all just a big coincidence. This is not correct. The AND gate protects\u00a0the audio sources from interfering with each other for a certain amount. I tested that, it simply sounds cleaner. At least I had a certain intention when I added the gates to the circuit (…not that I completely remember….). Looking at the circuit I am still wandering about _why_ but that’s one of the things that I file as ‘Audio things’ for now. [\/Edit]<\/p>\n <\/p>\n The signal is fed into the mixer and from the mixer sent to another Arduino which does the processing. the circuit looks like this:<\/p>\n To be honest: I cannot really remember where I got this circuit from. Somehow all the solutions I found while trying to find the circuit again look a little different. Again this might be spine.crawling for some of you but… it’s a fun project and it works. The code for the realtime audio-analysis is based on the FHT library by openmusiclabs<\/a> and expands an example I found over at dontquityourdayjob<\/a>.<\/p>\n \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/ \/\/ Adjust the Treshold – what volume should make it light up? \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/ \/\/ Delay – defines how many cycles before the lights will update.\u00a0 OML’s algorithm at 256 samples (needed for our 8 octaves) takes void setup() { \/********************************************************************************** int bassVal; int bassValOld; const int OUTTHRESHHOLD = 4;<\/p>\n void loop() { sei(); \/\/ if we’re at the end of the array… \/\/ calculate the average: \/\/Werte: bassVal = map(bassVal, -450, -390, 0, 127); if((bassVal > bassValOld+OUTTHRESHHOLD) || (bassVal < bassValOld-OUTTHRESHHOLD)){ if((midVal > midValOld+OUTTHRESHHOLD) || (midVal < midValOld-OUTTHRESHHOLD)){ if((hiVal > hiValOld+OUTTHRESHHOLD) || (hiVal < hiValOld-OUTTHRESHHOLD)){ <\/p>\n The whole mechanism is not THAT precise but it gets the job done and it’s a fun thing to watch. The bass-frequency has to be smoothed-out quite a bit in order to make it all work. After spending a little more than a day with this some might ask “what for?”. I tell you what for: for the sake of finally doing it. I had this idea for over a year now and it was well worth trying.<\/p>\n The system is quite slow in its reaction (mainly caused by the necessary smoothing) and results are still a bit unpredictable but turning an audio-mixer into a midi-controller just by using hardware of ~10\u20ac ain’t too bad, isn’t it?<\/p>\n <\/p>\n [tube]https:\/\/www.youtube.com\/watch?v=u5r6i65eHKk, 720, 540[\/tube]<\/p>\n","protected":false},"excerpt":{"rendered":" Or: Creating an audio-signal with an Arduino, feeding it into a mixing desk, altering the frequencies via the mixer’s eq and analyzing the processed audio with another Arduino which then turns it into a MIDI-signal. Yes, that is Digital-to-Analog-to-Digital-to-Analog-to-Digital-conversion. Phew! Here’s a picture of the setup: On the left side \u2026 Continue reading
\npinMode(3, OUTPUT);
\n}<\/p>\n
\nbuzz(3,480,100);
\n}<\/p>\n
\nlong delayValue = 1000000\/frequency\/2; \/\/ calculate the delay value between transitions
\nlong numCycles = frequency * length\/ 1000; \/\/ calculate the number of cycles for proper timing
\nfor (long i=0; i < numCycles; i++){ \/\/ for the calculated length of time…
\ndigitalWrite(targetPin,HIGH); \/\/ write the buzzer pin high to push out the diaphram
\ndelayMicroseconds(delayValue); \/\/ wait for the calculated delay value
\ndigitalWrite(targetPin,LOW); \/\/ write the buzzer pin low to pull back the diaphram
\ndelayMicroseconds(delayValue); \/\/ wait again or the calculated delay value
\n}
\n}<\/p>\n<\/a><\/p>\n<\/a><\/p>\n
\n\/\/ Easy Customizations
\n\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/<\/p>\n
\n#define THRESHOLD 40
\n\/\/ Attempt to ‘zero out’ noise when line in is ‘quiet’.\u00a0 You can change this to make some segments more sensitive.
\nint\u00a0 oct_bias[] = { 600, 600, 1, 100, 50, 50, 50, 50\u00a0 };
\n\/\/ Divide Threshold by 2 for top octave? 1 – yes 2 – no.\u00a0 Makes highest frequency blink more.
\n#define TOP_OCTAVE_DIVIDE false<\/p>\n
\n\/\/ Hard Customizations – know what you are doing, please.
\n\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
\n\/\/ FHT defaults – don’t change without reading the Open Music Labs documentation at openmusiclabs.com
\n#define LOG_OUT 0 \/\/ use the log output function
\n#define FHT_N 256 \/\/ set to 256 point fht
\n#define OCTAVE 1
\n#define OCT_NORM 1<\/p>\n
\n\/\/ 3.18 ms per cycle, so we essentially throw out 14 cycles (I used mechanical relays, you can lower this for solid state relays).
\n\/\/ 15 cycles = 47.7 ms update rate.\u00a0 Be careful here and don’t change it too quickly!\u00a0 I warned you!
\n#define DELAY 15
\n#include <FHT.h> \/\/ include the library
\n#include <MIDI.h><\/p>\n
\nSerial.begin(31250); \/\/ use the serial port
\nTIMSK0 = 0; \/\/ turn off timer0 for lower jitter
\nADCSRA = 0xe5; \/\/ set the adc to free running mode
\nADMUX = 0x40; \/\/ use adc0
\nDIDR0 = 0x01; \/\/ turn off the digital input for adc0
\n}<\/p>\n
\nLoop – includes initialization function and the full loop
\n**********************************************************************************\/
\nconst int NUMREADINGS=10;
\nint readings[NUMREADINGS];\u00a0\u00a0\u00a0\u00a0\u00a0 \/\/ the readings from the analog input
\nint index = 0;\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \/\/ the index of the current reading
\nint total = 0;\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \/\/ the running total
\nint average = 0;<\/p>\n
\nint midVal;
\nint hiVal;<\/p>\n
\nint midValOld;
\nint hiValOld;<\/p>\n
\n\/\/ True full loop
\nint q = 0;
\nwhile(1) { \/\/ reduces jitter
\ncli();\u00a0 \/\/ UDRE interrupt slows this way down on arduino1.0
\nfor (int i = 0 ; i < FHT_N ; i++) { \/\/ save 256 samples
\nwhile(!(ADCSRA & 0x10)); \/\/ wait for adc to be ready
\nADCSRA = 0xf5; \/\/ restart adc
\nbyte m = ADCL; \/\/ fetch adc data
\nbyte j = ADCH;
\nint k = (j << 8) | m; \/\/ form into an int
\nk -= 0x0200; \/\/ form into a signed int
\nk <<= 6; \/\/ form into a 16b signed int
\nfht_input[i] = k; \/\/ put real data into bins
\n}
\nfht_window(); \/\/ window the data for better frequency response
\nfht_reorder(); \/\/ reorder the data before doing the fht
\nfht_run(); \/\/ process the data in the fht
\nfht_mag_octave(); \/\/ take the output of the fht<\/p>\n
\nif (q % DELAY == 0) {
\n\/\/—-Smoothing
\n\/\/ subtract the last reading:
\ntotal= total – readings[index];
\n\/\/ read from the sensor:
\nreadings[index] = (fht_oct_out[1] – oct_bias[1]);
\n\/\/ add the reading to the total:
\ntotal= total + readings[index];
\n\/\/ advance to the next position in the array:
\nindex = index + 1;<\/p>\n
\nif (index >= NUMREADINGS)
\n\/\/ …wrap around to the beginning:
\nindex = 0;<\/p>\n
\naverage = total \/ NUMREADINGS;
\n\/\/—-<\/p>\n
\nbassVal = average;\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \/\/ : Bass
\nmidVal = fht_oct_out[4] – oct_bias[4];\u00a0\u00a0\u00a0 \/\/ Mitte
\nhiVal = fht_oct_out[7] – oct_bias[7];\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \/\/Hochton<\/p>\n
\nmidVal = map(midVal, 9, 107, 0, 127);
\nhiVal = map(hiVal, -34, 20, 0, 127);<\/p>\n
\nif((bassVal>=0) && (bassVal<=127)){
\nSerial.write(0xb0);
\nSerial.write(0x01);
\nSerial.write(bassVal);
\n}
\nbassValOld = bassVal;
\n}<\/p>\n
\nif((midVal>=0) && (midVal<=127)){
\nSerial.write(0xb0);
\nSerial.write(0x02);
\nSerial.write(midVal);
\n}
\nmidValOld = midVal;
\n}<\/p>\n
\nif((hiVal>=0) && (hiVal<=127)){
\nSerial.write(0xb0);
\nSerial.write(0x03);
\nSerial.write(hiVal);
\n}
\nhiValOld = hiVal;
\n}
\n}
\n++q;
\n}
\n}<\/p>\n