CSOUND Português
CSOUND AND ARDUINO
It is the intention of this chapter to suggest a number of ways in which Csound can be paired with an Arduino prototyping circuit board. It is not the intention of this chapter to go into any detail about how to use an Arduino, there is already a wealth of information available elsewhere online about this. It is common to use an Arduino and Csound with another program functioning as an interpreter so therefore some time is spent discussing these other programs.
An Arduino is a simple microcontroller circuit board that has become enormously popular as a component in multidisciplinary and interactive projects for musicians and artists since its introduction in 2005. An Arduino board can be programmed to do many things and to send and receive data to and from a wide variety of other components and devices. As such it is impossible to specifically define its function here. An Arduino is normally programmed using its own development environment (IDE). A program is written on a computer which is then uploaded to the Arduino; the Arduino then runs this program, independent of the computer if necessary. Arduino's IDE is based on that used by Processing and Wiring. Arduino programs are often referred to as "sketches". There now exists a plethora of Arduino variants and even a number of derivatives and clones but all function in more or less the same way.
Interaction between an Arduino and Csound is essentially a question of communication and as such a number of possible solutions exist. This chapter will suggest several possibilities and it will then be up to the user to choose the one most suitable for their requirements. Most Arduino boards communicate using serial communication (normally via a USB cable). A number of Arduino programs, called "Firmata", exist that are intended to simplify and standardise communication between Arduinos and software. Through the use of a Firmata the complexity of Arduino's serial communication is shielded from the user and a number of simpler objects, ugens or opcodes (depending on what the secondary software is) can instead be used to establish communication. Unfortunately Csound is rather poorly served with facilities to communicate using the Firmata (although this will hopefully improve in the future) so it might prove easiest to use another program (such as Pd or Processing) as an intermediary between the Arduino and Csound.
Arduino - Pd - Csound
First we will consider communication between an Arduino (running a Standard Firmata) and Pd. Later we can consider the options for further communication from Pd to Csound.
Assuming that the Arduino IDE (integrated development environment) has been installed and that the Arduino has been connected, we should then open and upload a Firmata sketch. One can normally be found by going to File -> Examples -> Firmata -> ... There will be a variety of flavours from which to choose but "StandardFirmata" should be a good place to start. Choose the appropriate Arduino board type under Tools -> Board -> ... and then choose the relevant serial port under Tools -> Serial Port -> ... Choosing the appropriate serial port may require some trial and error but if you have chosen the wrong one this will become apparent when you attempt to upload the sketch. Once you have established the correct serial port to use, it is worth taking a note of which number on the list (counting from zero) this corresponds to as this number will be used by Pd to communicate with the Arduino. Finally upload the sketch by clicking on the right-pointing arrow button.
Assuming that Pd is already installed, it will also be necessary to install an add-on library for Pd called Pduino. Follow its included instructions about where to place this library on your platform and then reopen Pd. You will now have access to a set of Pd objects for communicating with your Arduino. The Pduino download will also have included a number of examples Pd. "arduino-test.pd" will probably be the best patch to start. First set the appropriate serial port number to establish communication and then set Arduino pins as "input", "output" etc. as you desire. It is beyond the scope of this chapter to go into further detail regarding setting up an Arduino with sensors and auxiliary components, suffice to say that communication to an Arduino is normally tested by 'blinking' digital pin 13 and communication from an Arduino is normally tested by connecting a 10 kilo-ohm (10k) potentiometer to analog pin zero. For the sake of argument, we shall assume in this tutorial that we are setting the Arduino as a hardware controller and have a potentiometer connected to pin 0.
This picture below demonstrates a simple Pd patch that uses Pduino's objects to receive communication from Arduino's analog and digital inputs. (Note that digital pins 0 and 1 are normally reserved for serial communication if the USB serial communication is unavailable.) In this example serial port '5' has been chosen. Once the analogIns enable box for pin 0 is checked, moving the potentiometer will change the values in the left-most number box (and move the slider connected to it). Arduino's analog inputs output integers with 10-bit resolution (0 - 1023) but these values will often be rescaled as floats within the range 0 - 1 in the host program for convenience.
Having established communication between the Arduino and Pd we can now consider the options available to us for communicating between Pd and Csound. The most obvious (but not necessarily the best or most flexible) method is to use Pd's csoundapi~ object (csound6~ in Csound6). The above example could be modified to employ csoundapi~ as shown below.
The outputs from the first two Arduino analog controls are passed into Csound using its API. Note that we should use the unpegged (not quantised in time) values directly from the 'route' object. The Csound .csd file 'control.csd' is called upon by Pd and it should reside in the same directory as the Pd patch. Establishing communication to and from Pd could employ code such as that shown below. Data from controller one (Arduino analog 0) is used to modulate the amplitude of an oscillator and data from controller two (Arduino analog 1) varies its pitch across a four octave range.
EXAMPLE 08B01_Pd_to_Csound.csd
<CsoundSynthesizer>
<CsOptions>
</CsOptions>
<CsInstruments>
sr = 44100
nchnls = 2
0dbfs = 1
ksmps = 32
instr 1
; read in controller data from Pd via the API using 'invalue'
kctrl1 invalue "ctrl1"
kctrl2 invalue "ctrl2"
; re-range controller values from 0 - 1 to 7 - 11
koct = (kctrl2*4)+7
; create an oscillator
a1 vco2 kctrl1,cpsoct(koct),4,0.1
outs a1,a1
endin
</CsInstruments>
<CsScore>
i 1 0 10000
e
</CsScore>
</CsoundSynthesizer>
Communication from Pd into Csound is established using the invalue opcodes and audio is passed back to Pd from Csound using outs. Note that Csound does not address the computer's audio hardware itself but merely passes audio signals back to Pd. Greater detail about using Csound within Pd can be found in the chapter Csound in Pd.
A disadvantage of using the method is that in order to modify the Csound patch it will require being edited in an external editor, re-saved, and then the Pd patch will need to be reloaded to reflect these changes. This workflow might be considered rather inefficient.
Another method of data communication between PD and Csound could be to use MIDI. In this case some sort of MIDI connection node or virtual patchbay will need to be employed. On Mac this could be the IAC driver, on Windows this could be MIDI Yoke and on Linux this could be Jack. This method will have the disadvantage that the Arduino's signal might have to be quantised in order to match the 7-bit MIDI controller format but the advantage is that Csound's audio engine will be used (not Pd's; in fact audio can be disabled in Pd) so that making modifications to the Csound .csd and hearing the changes should require fewer steps.
A final method for communication between Pd and Csound is to use OSC. This method would have the advantage that analog 10 bit signal would not have to be quantised. Again workflow should be good with this method as Pd's interaction will effectively be transparent to the user and once started it can reside in the background during working. Communication using OSC is also used between Processing and Csound so is described in greater detail below.
Arduino - Processing - Csound
It is easy to communicate with an Arduino using a Processing sketch and any data within Processing can be passed to Csound using OSC.
The following method makes use of the Arduino and P5 (glove) libraries for processing. Again these need to be copied into the appropriate directory for your chosen platform in order for Processing to be able to use them. Once again there is no requirement to actually know very much about Processing beyond installing it and running a patch (sketch). The following sketch will read all Arduino inputs and output them as OSC.
Start the Processing sketch by simply clicking the triangle button at the top-left of the GUI. Processing is now reading serial data from the Arduino and transmitting this as OSC data within the computer.
The OSC data sent by Processing can be read by Csound using its own OSC opcodes. The following example simply reads in data transmitted by Arduino's analog pin 0 and prints changed values to the terminal. To read in data from all analog and digital inputs you can use this example .csd.
EXAMPLE 08B02_Processing_to_Csound.csd
<CsoundSynthesizer>
<CsOptions>
-o dac
</CsOptions>
<CsInstruments>
sr = 44100
ksmps = 8
nchnls = 1
0dbfs = 1
; handle used to reference osc stream
gihandle OSCinit 12001
instr 1
; initialise variable used for analog values
gkana0 init 0
; read in OSC channel '/analog/0'
gktrigana0 OSClisten gihandle, "/analog/0", "i", gkana0
; print changed values to terminal
printk2 gkana0
endin
</CsInstruments>
<CsScore>
i 1 0 3600
e
</CsScore>
</CsoundSynthesizer>
Also worth in investigating is Jacob Joaquin's Csoundo - a Csound library for Processing. This library will allow closer interaction between Processing and Csound in the manner of the csoundapi~ object in Pd. This project has more recently been developed by Rory Walsh.
Arduino as a MIDI Device
Some users might find it most useful to simply set the Arduino up as a MIDI device and to use that protocol for communication. In order to do this all that is required is to connect MIDI pin 4 to the Arduino's 5v via a 200k resistor, to connect MIDI pin 5 to the Arduino's TX (serial transmit) pin/pin 1 and to connect MIDI pin 2 to ground, as shown below. In order to program the Arduino it will be necessary to install Arduino's MIDI library.
Programming an Arduino to generate a MIDI controller signal from analog pin 0 could be done using the following code:
// example written by Iain McCurdy
// import midi library
#include <MIDI.h>
const int analogInPin = A0; // choose analog input pin
int sensorValue = 0; // sensor value variable
int oldSensorValue = 0; // sensor value from previous pass
int midiChannel = 1; // set MIDI channel
void setup()
{
MIDI.begin(1);
}
void loop()
{
sensorValue = analogRead(analogInPin);
// only send out a MIDI message if controller has changed
if (sensorValue!=oldSensorValue)
{
// controller 1, rescale value from 0-1023 (Arduino) to 0-127 (MIDI)
MIDI.sendControlChange(1,sensorValue/8,midiChannel);
oldSensorValue = sensorValue; // set old sensor value to current
}
}
delay(10);
}
Data from the Arduino can now be read using Csound's ctrl7 opcodes for reading MIDI controller data.
The Serial Opcodes
Serial data can also be read directly from the Arduino by Csound by using Matt Ingalls' opcodes for serial communication: serialBegin and serialRead.
An example Arduino sketch for serial communication could be as simple as this:
// Example written by Matt Ingalls
// ARDUINO CODE:
void setup() {
// enable serial communication
Serial.begin(9600);
// declare pin 9 to be an output:
pinMode(9, OUTPUT);
}
void loop()
{
// only do something if we received something (this should be at csound's k-rate)
if (Serial.available())
{
// set the brightness of LED (connected to pin 9) to our input value
int brightness = Serial.read();
analogWrite(9, brightness);
// while we are here, get our knob value and send it to csound
int sensorValue = analogRead(A0);
Serial.write(sensorValue/4); // scale to 1-byte range (0-255)
}
}
It will be necessary to provide the correct address of the serial port to which the Arduino is connected (in the given example the Windows platform was being used and the port address was /COM4).
It will be necessary to scale the value to correspond to the range provided by a single byte (0-255) so therefore the Arduino's 10 bit analog input range (0-1023) will have to be divided by four.
EXAMPLE 08B03_Serial_Read.csd
; Example written by Matt Ingalls ; CSOUND CODE: ; run with a commandline something like: ; csound --opcode-lib=serialOpcodes.dylib serialdemo.csd -odac -iadc <CsoundSynthesizer> <CsOptions> </CsOptions> ;--opcode-lib=serialOpcodes.dylib -odac <CsInstruments> ksmps = 500 ; the default krate can be too fast for the arduino to handle 0dbfs = 1 instr 1 iPort serialBegin "/COM4", 9600 kVal serialRead iPort printk2 kVal endin </CsInstruments> <CsScore> i 1 0 3600 e </CsScore> </CsoundSynthesizer>
This example will read serial data from the Arduino and print it to the terminal. Reading output streams from several of Arduino's sensor inputs simultaneously will require more complex parsing of data within Csound as well as more complex packaging of data from the Arduino. This is demonstrated in the following example which also shows how to handle serial transmission of integers larger than 255 (the Arduino analog inputs have 10 bit resolution).
First the Arduino sketch, in this case reading and transmitting two analog and one digital input:
// Example written by Sigurd Saue
// ARDUINO CODE:
// Analog pins
int potPin = 0;
int lightPin = 1;
// Digital pin
int buttonPin = 2;
// Value IDs (must be between 128 and 255)
byte potID = 128;
byte lightID = 129;
byte buttonID = 130;
// Value to toggle between inputs
int select;
/*
** Two functions that handles serial send of numbers of varying length
*/
// Recursive function that sends the bytes in the right order
void serial_send_recursive(int number, int bytePart)
{
if (number < 128) { // End of recursion
Serial.write(bytePart); // Send the number of bytes first
}
else {
serial_send_recursive((number >> 7), (bytePart + 1));
}
Serial.write(number % 128); // Sends one byte
}
void serial_send(byte id, int number)
{
Serial.write(id);
serial_send_recursive(number, 1);
}
void setup() {
// enable serial communication
Serial.begin(9600);
pinMode(buttonPin, INPUT);
}
void loop()
{
// Only do something if we received something (at csound's k-rate)
if (Serial.available())
{
// Read the value (to empty the buffer)
int csound_val = Serial.read();
// Read one value at the time (determined by the select variable)
switch (select) {
case 0: {
int potVal = analogRead(potPin);
serial_send(potID, potVal);
}
break;
case 1: {
int lightVal = analogRead(lightPin);
serial_send(lightID, lightVal);
}
break;
case 2: {
int buttonVal = digitalRead(buttonPin);
serial_send(buttonID, buttonVal);
}
break;
}
// Update the select (0, 1 and 2)
select = (select+1)%3;
}
}
The solution is similar to MIDI messages. You have to define an ID (a unique number >= 128) for every sensor. The ID behaves as a status byte that clearly marks the beginning of a message received by Csound. The remaining bytes of the message will all have a most significant bit equal to zero (value < 128). The sensor values are transmitted as ID, length (number of data bytes), and the data itself. The recursive function serial_send_recursive counts the number of data bytes necessary and sends the bytes in the correct order. Only one sensor value is transmitted for each run through the Arduino loop.
The Csound code receives the values with the ID first. Of course you have to make sure that the IDs in the Csound code matches the ones in the Arduino sketch. Here's an example of a Csound orchestra that handles the messages sent from the Arduino sketch:
EXAMPLE 08B04_Serial_Read_multiple.csd
; Example written by Sigurd Saue ; CSOUND CODE: <CsoundSynthesizer> <CsOptions> -d -odac </CsOptions> <CsInstruments> sr = 44100 ksmps = 500 ; the default krate can be too fast for the arduino to handle nchnls = 2 0dbfs = 1 giSaw ftgen 0, 0, 4096, 10, 1, 1/2, 1/3, 1/4, 1/5, 1/6, 1/7, 1/8 instr 1 ; Initialize the three variables to read kPot init 0 kLight init 0 kButton init 0 iPort serialBegin "/COM5", 9600 ;connect to the arduino with baudrate = 9600 serialWrite iPort, 1 ;Triggering the Arduino (k-rate) kValue = 0 kType serialRead iPort ; Read type of data (pot, light, button) if (kType >= 128) then kIndex = 0 kSize serialRead iPort loopStart: kValue = kValue << 7 kByte serialRead iPort kValue = kValue + kByte loop_lt kIndex, 1, kSize, loopStart endif if (kValue < 0) kgoto continue if (kType == 128) then ; This is the potmeter kPot = kValue elseif (kType == 129) then ; This is the light kLight = kValue elseif (kType == 130) then ; This is the button (on/off) kButton = kValue endif continue: ; Here you can do something with the variables kPot, kLight and kButton ; printks "Pot %f\n", 1, kPot ; printks "Light %f\n", 1, kLight ; printks "Button %d\n", 1, kButton ; Example: A simple oscillater controlled by the three parameters kAmp port kPot/1024, 0.1 kFreq port (kLight > 100 ? kLight : 100), 0.1 aOut oscil kAmp, kFreq, giSaw if (kButton == 0) then out aOut endif endin </CsInstruments> <CsScore> i 1 0 60 ; Duration one minute e </CsScore> </CsoundSynthesizer>
Remember to provide the correct address of the serial port to which the Arduino is connected (the example uses "/COM5").
HID
Another option for communication has been made available by a new Arduino board called "Leonardo". It pairs with a computer as if it were an HID (Human Interface Device) such as a mouse, keyboard or a gamepad. Sensor data can therefore be used to imitate the actions of a mouse connected to the computer or keystrokes on a keyboard. Csound is already equipped with opcodes to make use of this data. Gamepad-like data is perhaps the most useful option though and there exist opcodes (a least in the Linux version) for reading gamepad data. It is also possible to read in data from a gamepad using pygame and Csound's python opcodes.