Forums > MaxMSP

synchronize Arduino with [metro] initialization

Mar 03 2013 | 10:46 am

Hallo all

I have the following code running in Arduino, which detects force from multiple FSRs and assigns each a unique ID so I can parse the sensors in Max:

//read 12 FSRs, convert force value to LED brightness

int inVal;
int brightness;

void setup(){
//multiple LED pins/////////
for(int x=2; x<14; x++){
pinMode(x, OUTPUT);

void loop(){
//multiple FSR pins
for(int i=0; i<12; i++){
inVal = analogRead (i);
inVal=constrain(inVal, 0, 255);

//prepend sensor value with pin# ident
analogWrite((i+2), brightness);

My problem is the fact that the Arduino code is continually running, sending sensor ID and value – for example, at any time it could be sending "5, 0; 6, 0; 7, 143; 8, 0; when I begin polling the serial port I might get EITHER the sensor value first followed by sensor ident, OR ident then value. I thought that a solution might be to only send the data to MaxMSP when a sensor is pressed. Would the following result in jittery data?

if sensorVal >0{
send all the data;
blank space here;

Or is another solution to get Arduino to listen to the serial port and wait for a keystroke or ascii value (from MaxMSP). I know how to send stuff from Arduino to Max, but have no idea how to do this the other way round. What I wish to achieve is a guarantee that whenever I begin polling the serial port I will always get sensor ident FIRST, followed by the associated sensor value.

Any suggestions?

Mar 03 2013 | 12:19 pm

or offset the sensor ident so they’re easier to distinguish? That way you can easily parse.

Mar 03 2013 | 1:45 pm

Hi Wetteberg

what exactly is meant by "offset"?

Sensor idents are between 0 and 11; sensor data is between 0-255. Ah yes, do you mean scale idents up to >255? How would I then parse this in Max, to ensure synchronization (ident first, always; value second always)?

Best regards

on the Arduino forum, someone suggested sending only data when a sensor changes, not 100% sure how to do that either. I’ll have a noodle around and get back…….

Mar 03 2013 | 1:59 pm

well it is a bit more complicated to have to look for value pairs, but [match my_ident_above_255 nn] would get a specific pair and ensure the sync, as far as I can tell.

And yeah, some filtering is always good before hitting the computer :)

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