HC-05/Arduino receiving spam data

Question

I connected everything properly. On the first try I did receive data as I was supposed to. I then wrote some logic, re-uploaded and started receiving crazy spam.

My serial monitor is getting spammed with:

• question marks if the variable is char, or;
• 25252525252 if the variable is int, or;
• -1 if variable is String.

I'm monitoring at 38400 baud which is the same as my Serial.begin().

Any ideas ?

Code:

#include <Wire.h>
#include <Adafruit_PWMServoDriver.h>
Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver();
#define MIN_PULSE_WIDTH 650
#define MAX_PULSE_WIDTH 2350
#define DEFAULT_PULSE_WIDTH 1500
#define FREQUENCY 50
char data = 'a';
void setup()
{
 analogReference(DEFAULT);
 Serial.begin(38400);
 pwm.begin();
 pwm.setPWMFreq(FREQUENCY);
 Serial.println("hello world");
}
void loop()
{
 data = Serial.read();
 Serial.println(data);
 Serial.flush();
 if (data == 'a'){
 pwm.setPWM(0, 0, pulseWidth(90));
 }
 if (data == 's'){
 pwm.setPWM(0, 0, pulseWidth(30));
 }
 delay(1000);
 //printing time in seconds 
}
int pulseWidth(int angle)
{
 int pulse_wide, analog_value;
 pulse_wide = map(angle, 0, 180, MIN_PULSE_WIDTH, MAX_PULSE_WIDTH);
 analog_value = int(float(pulse_wide) / 1000000 * FREQUENCY * 4096);
 return analog_value;
}

• Stoil: Thanks, that seems to work for the spam. I changed my variable to integer and tried sending a number. No matter what I send, I receive either 120, 128 or 248, multiple times. What's the deal ?
• Juraj: you should first connect the Arduino to Serial Monitor and learn the basics of Serial communication on examples
• Stoil: It does, but why is it the same no matter what character I send ?
• Stoil: I cannot use answer since I am not logged in, which I cannot do since I have my password on remember on another machine. I changed print to write, however I still am getting weird results. 1 corresponds to "x?" (with a reverse question mark) and 2 corresponds to "???". I'm so lost.
• Juraj: has the BT module a baud rate 38400 baud?

Answer 1

Serial.read() returns -1 if no data is available. It doesn't wait for the byte. Test for -1 or use Serial.available() as any example does.

Replace Serial.print(data) with Serial.write(data) to get the data echoed back unchanged.