# Speed up arduino

Hi, currently my program is too slow(120Hz) for me system requirement(~2kHz). May I know how to speed up my arduino by changing the code? I discover that "analogRead", "division","map" function, "square root" slow down my system. Is there any more advance of coding method to speed up the arduino?

Regards, Chao Hong

(deleted)

code like below, when I include the as below in the system, the sampling rate of the whole system become significantly slower.

analogRead(1); fsrVoltage = map(fsrReading, 0, 1023, 0, 5000); V_Conversion = 1 / (1+V1)^2 ; //any normal divide method, can change by using shift method? How? ,Amplitude = sqrt(v*v + x*x);

Learn how to implement without floating point. If you want more details you should post your code and not just snippets of it.

`````` V_Conversion = 1 / (1+V1)^2 ;
``````

What does the XOR do in that expression?

What does the XOR do in that expression?

making it slow ;)

more serious, think the OP meant - V_Conversion = 1 / ((1+V1) * (1 + V1)) ;

this is a formula that only makes sense in the float domain as in the integer domain it will mostly return 0, 1 or a divide by zero .

So the trick should be to map the formulas in the integer domain without los of precission. Eg. instead of doing math in volts do it in millivolts.

fsrVoltage = map(fsrReading, 0, 1023, 0, 5000); is fast code. If you allow an error you could do

fsrVoltage = fsrReading * 5; // error 2-3% can be acceptible (?)

analogRead(1); can be replaced by fastAnalogRead(1) which is 10x faster ==> search the forum (upper right)

So please post your code then we can have a look ! And tell us as much as you can about the goal of the project, sensors actuators and please post relevant datalinks...

, think the OP meant - V_Conversion = 1 / ((1+V1) * (1 + V1)) ;

Yes, I thought that too, but wouldn't it have wasted less time if the OP had posted actual code?

Just another thought.

@ OP - there is. Have you considered doing your calculations working with (possibly improper) fractions with a common denominator of 1023? It's a lot more think-work if you aren't used to doing integer math, but it works a lot faster - and can sometimes actually provide more accurate results than working with floats...

If it's a finished product (ie you're done adding features), you could put all the slow formulas in a lookup table.

robtillaart:

What does the XOR do in that expression?

more serious, think the OP meant - V_Conversion = 1 / ((1+V1) * (1 + V1)) ;

Ya, that is the purpose of the code.

analogRead(1); can be replaced by fastAnalogRead(1) which is 10x faster ==> search the forum (upper right)

I have found this but the sampling rate still same. http://arduino.cc/forum/index.php/topic,74895.0.html http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1208715493/11

and if I want to use fastAnalogRead(1), do I need to include any library? as it return me error say the fastAnalogRead is not declared.

hong89: May I know how to speed up my arduino by changing the code?

What code?

hong89: I discover that "analogRead", "division","map" function, "square root" slow down my system.

Yes, instructions tend to do that.

hong89: Is there any more advance of coding method to speed up the arduino?

hong89: Is there any more advance of coding method to speed up the arduino?

[/quote]

the code that help to decrease proccesing time of arduino by replacing analogRead() and devision method with other method of coding.

So you could do 10000 of them a second.

... currently my program is too slow(120Hz) ...

So that does not explain why you are getting 120 when you could have 10000. So if you post your code then we could see the problem. If not, well ...

here is my code. Thanks for the help =)

currently my code running at rate of 600Hz, but I need sampling rate up to 2kHz.
I check the sampling rate by setting high and low at one of the digital pin and monitor with scopemeter.

``````void Position_Count()
{
double p=0;
double a1 = 0;
double b1 = 0;

if(A==1 && a1!=A)
{
if(B==1)
{
p=p-1;
a1=1;
b1=1;
}
count=p;
}

if(A==1 && a1!=A)
{
if(B==0)
{
p=p+1;
a1=1;
b1=0;
}
count=p;
}

if(A==0 && a1!=A)
{
if(B==1)
{
p=p+1;
a1=0;
b1=1;
}
count=p;
}

if(A==0 && a1!=A)
{
if(B==0)
{
p=p-1;
a1=0;
b1=0;
}
count=p;
}

if(B==1 && b1!=B)
{
if(A==1)
{
p=p+1;
b1=1;
a1=1;
}
count=p;
}

if(B==1 && b1!=B)
{
if(A==0)
{
p=p-1;
b1=1;
a1=0;
}
count=p;
}

if(B==0 && b1!=B)
{
if(A==1)
{
p=p-1;
b1=0;
a1=1;
}
count=p;
}

if(B==0 && b1!=B)
{
if(A==0)
{
p=p+1;
b1=0;
a1=0;
}
count=p;
}

}
``````
``````void Force()
{

// analog voltage reading ranges from about 0 to 1023 which maps to 0V to 5V (= 5000mV)
fsrVoltage = map(fsrReading, 0, 1023, 0, 5000);

// The voltage = Vcc * R / (R + FSR) where R = 10K and Vcc = 5V
// so FSR = ((Vcc - V) * R) / V
fsrResistance = 5000 - fsrVoltage;     // fsrVoltage is in millivolts so 5V = 5000mV
fsrResistance *= 10000;                // 10K resistor
fsrResistance = fsrVoltage;

fsrConductance = 1000000;           // we measure in micromhos so
fsrConductance = fsrResistance;

// Use the two FSR guide graphs to approximate the force
if (fsrConductance <= 100)
{
fsrForce = fsrConductance + 20;
}

/    else
{
fsrForce = fsrConductance ;
fsrForce = 50;
}

fsrForce = fsrForce*3;
}
``````
``````void Virtual_System(double maxampl, double SollAmpl, double Kp, double Damp, int Mass )
{
double Amplitude, P_ampl;
double Sum;
double dampingValue, Damping;
double Vset;
double acceleration, acceleration2;

//  Amplitude = sqrt(v*v + x*x);

// C code for dampingValue, if...else
if(Amplitude >= maxampl && Amplitude <= maxampl+0.05)
{
dampingValue = 0.1*Vset;
}
else if(Amplitude > maxampl+0.05)
{
dampingValue = 0.3*Vset;
}
else if(Amplitude > maxampl+0.1)
{
dampingValue = 10*Vset;
}
else
{
dampingValue = 0;
}

P_ampl = Amplitude - SollAmpl;

Damping = P_ampl*Kp;

Sum = Vset*Damping;

acceleration = 0 - dampingValue - Sum - Vset*Damp - x*w ;//- ;//SatForce/Mass;

double V_Conversion;

if(v >= 0)
{
V_Conversion = 1 / ((1+V1)*(1+V1)) ;
}
else
{
V_Conversion = 1 / ((1-V1)*(1-V1)) ;
}

acceleration2 = acceleration*V_Conversion;

// v = integrate of acceleration2
v = v + acceleration2;

Potential();
w = Freq * 2*PI/60 ;

Vset = v*w - PosGain;

//x = integrate of Vset
x = x + Vset*Sampletime ;

}
``````

How about a complete application? That code won't even compile.

``````fsrConductance = 1000000;           // we measure in micromhos so
fsrConductance = fsrResistance;
``````

I suppose you can hope the compiler optimises-out pointless assignments.

``````int A,B,C ;
int fsrPin = 0;     // the FSR and 10K pulldown are connected to a0
int fsrVoltage;     // the analog reading converted to voltage
unsigned long fsrResistance;  // The voltage converted to resistance, can be very big so make "long"
unsigned long fsrConductance;
long fsrForce;       // Finally, the resistance converted to force
int count = 0;      //count of position
double Force_corr, Pos_corr;
int Status_out, enable, Regler_Start, Init_Start, corr_Start, Auto_Status;
int Enable;        //emergency stop

double SettingValue, PosGain;
double x, Sampletime,v, w;
double SatForce;

int V1;
double Freq;

double clock;

int state = HIGH;

void setup()
{
Serial.begin(9600);
Status_out = enable = Regler_Start = Init_Start = corr_Start = Auto_Status = 0 ;
Enable = 1;
attachInterrupt(4, emergency, RISING);   //interupt 4 , digital pin 19
state = HIGH;

}

void loop()
{

digitalWrite (10, state);

Position_Count();
Force();
Flow_Control(2);

Correction(fsrForce, count, corr_Start);

if (Regler_Start == 0)
{
int f = 0-10*25;
Pos_SetValue(353.81,3.8095,22.8571);

Force_SetValue(f);
Potential();
Virtual_System(0.099048,0.2,0,-0.04,150);
}
else
{

}

state =!state;
}

void Position_Count()
{
int p=0;
int a1 = 0;
int b1 = 0;

if(A==1 && a1!=A)
{
if(B==1)
{
p=p-1;
a1=1;
b1=1;
}
count=p;
}

if(A==1 && a1!=A)
{
if(B==0)
{
p=p+1;
a1=1;
b1=0;
}
count=p;
}

if(A==0 && a1!=A)
{
if(B==1)
{
p=p+1;
a1=0;
b1=1;
}
count=p;
}

if(A==0 && a1!=A)
{
if(B==0)
{
p=p-1;
a1=0;
b1=0;
}
count=p;
}

if(B==1 && b1!=B)
{
if(A==1)
{
p=p+1;
b1=1;
a1=1;
}
count=p;
}

if(B==1 && b1!=B)
{
if(A==0)
{
p=p-1;
b1=1;
a1=0;
}
count=p;
}

if(B==0 && b1!=B)
{
if(A==1)
{
p=p-1;
b1=0;
a1=1;
}
count=p;
}

if(B==0 && b1!=B)
{
if(A==0)
{
p=p+1;
b1=0;
a1=0;
}
count=p;
}

}

void Force()
{

// analog voltage reading ranges from about 0 to 1023 which maps to 0V to 5V (= 5000mV)
//  fsrVoltage = map(fsrReading, 0, 1023, 0, 5000);

// The voltage = Vcc * R / (R + FSR) where R = 10K and Vcc = 5V
// so FSR = ((Vcc - V) * R) / V        yay math!
fsrResistance = 5000 - fsrVoltage;     // fsrVoltage is in millivolts so 5V = 5000mV
fsrResistance *= 10000;                // 10K resistor
fsrResistance /= fsrVoltage;

fsrConductance = 1000000;           // we measure in micromhos so
fsrConductance /= fsrResistance;

// Use the two FSR guide graphs to approximate the force
if (fsrConductance <= 100)                  //range 0-2N
{
fsrForce = fsrConductance /20;
//      Serial.print("Force in Newtons: ");
//      Serial.println(fsrForce);
}

else
{
fsrForce = fsrConductance /50;                //range 80N-100N
//      fsrForce /= 50;
}

fsrForce = fsrForce*3;
}

void Force2()
{

// analog voltage reading ranges from about 0 to 1023 which maps to 0V to 5V (= 5000mV)
// fsrVoltage = map(fsrReading, 0, 1023, 0, 5000);

// The voltage = Vcc * R / (R + FSR) where R = 10K and Vcc = 5V
// so FSR = ((Vcc - V) * R) / V        yay math!
fsrResistance = 5000 - fsrVoltage;     // fsrVoltage is in millivolts so 5V = 5000mV
fsrResistance *= 10000;                // 10K resistor
fsrResistance /= fsrVoltage;

fsrConductance = 1000000;           // we measure in micromhos so
fsrConductance /= fsrResistance;

// Use the two FSR guide graphs to approximate the force
if (fsrConductance <= 100)                  //range 0-2N
{
fsrForce = fsrConductance /20;
//      Serial.print("Force in Newtons: ");
//      Serial.println(fsrForce);
}

else
{
fsrForce = fsrConductance /50;                //range 80N-100N
//      fsrForce /= 50;
}

fsrForce = fsrForce*3;
}

void Correction(double Force, double Position, int Reset)
{
int mtime = 0;
int force = 0;
int pos = 0;
int mreset = 0;

if(Reset==1 && mreset==0)
{
if(mtime==0)
{
mtime = clock;
}
if(mtime >= 0)
{
if(clock>(mtime + 5))
{
force = Force;
pos = Position;
mreset = 1;
}
}
}
if(Reset==0)
{
mreset=0;
mtime=0;
}
Force_corr = force;
Pos_corr = pos;

}

void Flow_Control(int Status)
{
// int Status_out, enable, Regler_Start, Init_Start, corr_Start, Auto_Status;
//   Status_out = enable = Regler_Start = Init_Start = corr_Start = Auto_Status = 0;

Status_out=Status;    //Status = input,   Status_out = output
if(Enable==1)         //Enable = input,   enable = output
{
if(Status==0)
{
enable=0;
}

if(Status==1)
{
enable=4.5;
Init_Start = 1;
}
else
{
Init_Start = 0;
}

if(Status==2)
{
enable=0;
corr_Start=1;
}
else
{
corr_Start=0;
}

if(Status==3)
{
enable=4.5;
Regler_Start=1;
}
else
{
Regler_Start=0;
}
}
if(Enable==0)
{
enable==0;
Regler_Start=0;
corr_Start=0;
Auto_Status=0;
}
}

void emergency()
{
Enable = 0;
}

// Pos_SetValue(353.81, 3.8095, 22.8571 )
void Pos_SetValue(double P_Person, double I_Gain, double D_Gain)
{
double istPosition ;
double SetValue;
double PosDiff;
int Position;

Position = count - Pos_corr;

istPosition = Position *0.007;
PosDiff = x - Position;

double intPosDiff;

//intPosDiff ---> integration of PosDiff
intPosDiff += PosDiff*Sampletime;

SetValue = v*w*D_Gain + PosDiff*P_Person +I_Gain*intPosDiff;

// SettingValue ---> go through saturation function
if(SetValue >= 10)
{
SettingValue = 10;
}

else if(SetValue <= -10)
{
SettingValue = -10;
}

else
{
SettingValue = SetValue;   // Output Setting Value to control motor
}

PosGain = SetValue - SettingValue;

}

/////////  Force_SetValue( -10*25 / -5*15, )
void Force_SetValue(int Ks)
{
int Force;
double SetForce;

Force = fsrForce - Force_corr;

SetForce = x*Ks -23*Force;

// SatForce --> SetForce go through saturation

if(SetForce >= 50)
{
SatForce = 50;
}

else if(SetForce <= -50)
{
SatForce = -50;
}

else
{
SatForce = SetForce;   // Output Setting Value to control motor
}
}

/////////////////// Virtual_System(0.099048, 0.2, ??, -0.04, 150)
void Virtual_System(double maxampl, double SollAmpl, double Kp, double Damp, int Mass )
{
double Amplitude, P_ampl;
double Sum;
double dampingValue, Damping;
double Vset;
double acceleration, acceleration2;

Amplitude = sqrt(v*v + x*x);

// C code for dampingValue, if...else
if(Amplitude >= maxampl && Amplitude <= maxampl+0.05)
{
dampingValue = 0.1*Vset;
}
else if(Amplitude > maxampl+0.05)
{
dampingValue = 0.3*Vset;
}
else if(Amplitude > maxampl+0.1)
{
dampingValue = 10*Vset;
}
else
{
dampingValue = 0;
}

P_ampl = Amplitude - SollAmpl;

Damping = P_ampl*Kp;

Sum = Vset*Damping;

acceleration = 0 - dampingValue - Sum - Vset*Damp - x*w - SatForce/Mass;

double V_Conversion;

if(v >= 0)
{
V_Conversion = 1 / ((1+V1)*(1+V1)) ;
}
else
{
V_Conversion = 1 / ((1-V1)*(1-V1)) ;
}

acceleration2 = acceleration*V_Conversion;

// v = integrate of acceleration2
v = v + acceleration2;

Potential();
w = Freq * 2*PI/60 ;

Vset = v*w - PosGain;

//x = integrate of Vset
x = x + Vset*Sampletime ;

}

void Potential()
{
int PotentioPin = 2;
int Potentiometer;

// Potentiometer reading ranges from about 0 to 1023 which maps to 0V to 5V (= 5000mV)
//  Potentiometer = map(PotentioReading, 0, 934, -2500, 2500);

double U;
U = Potentiometer;

{
Freq = floor((8+3*U)*4+0.5)/4;
}
else
{
Freq = 1;
}
}
``````
``````  Status_out = enable = Regler_Start = Init_Start = corr_Start = Auto_Status = 0 ;
Enable = 1;
``````

It's generally not a good thing to use variables that differ only in case. When I see that, I usually quit reading.

``````        enable=4.5;
``````

enable is an int!

``````Status_out = enable = Regler_Start = Init_Start = corr_Start = Auto_Status = 0 ;
``````

Don't you trust the compiler to have done this for you?

AWOL: ``` Status_out = enable = Regler_Start = Init_Start = corr_Start = Auto_Status = 0 ; ```

Don't you trust the compiler to have done this for you?

I think this not the reason make my system slow right?