Infinity appears at Constant block in Simulink

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Matthew Tieu
Matthew Tieu el 12 de Nov. de 2022
Comentada: Matthew Tieu el 12 de Nov. de 2022
I am making a Simulink program to measure the analog output of a circuit using an Arduino Uno. Since it is not possible to change the PWM frequency using the provided MATLAB blocks, I have included an S-function builder block to include Arduino code. As seen in the screenshot below, when I run the program (either in external or connected I/O mode), the value at the constant block (duty cycle) is infinity. This gives an incorrect graph at the scope.
I am not sure what I have done wrong since the same code works properly in the Arduino IDE. My includes are:
#include <math.h>
#include <Arduino.h>
The start wrapper code is:
pinMode(6,OUTPUT); // Pin D6 generates the PWM wave
TCCR0B = bit(CS01); // Set PWM frequency as 7812.5 Hz
pinMode(16,INPUT); // Pin A2 measures the output
The output wrapper code in the S function builder block is:
int fraction = round(duty[0]*2.55);
analogWrite(6,fraction); // Change PWM duty cycle based on input
a2[0] = analogRead(16); // Output is the value read from pin A2
I have set the number of discrete states to 1. For extra info, this is not for homework and the same problem occurs in my other Simulink programs that require input(s) to an S-function Builder block. I will appreciate any explanation for the issue that I am experiencing currently. Thanks in advance.

Respuesta aceptada

Paul el 12 de Nov. de 2022
That “inf” is the sample time of the constant block. As is the “D1” on the other blocks. Check the Simulink doc on sample times for more info.
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Matthew Tieu
Matthew Tieu el 12 de Nov. de 2022
Ok thanks for the clarification. I thought that was the output value coming out of the block.

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