Serial data changes when using Arduino Pro Trinket vs. Uno

Question

I'm noticing my data is not changing with an Arduino Pro Trinket. The data is being sent from a spectrometer. More light= higher numbers. The code I am using works fine with an Arduino Uno (same number of values coming in, but with a range going from 95 to 1000) while the Trinket ranges from 173-184ish.

Could this be an FTDI connection issue? (It is kind of poorly soldered)

Or is the Trinket not capable of gathering these numbers?

Do I have to change something my code?

Code is here:

/*
 * Macro Definitions
 */
#define SPEC_TRG         A0
#define SPEC_ST          A1
#define SPEC_CLK         A2
#define SPEC_VIDEO       A3

#define SPEC_CHANNELS    288 // New Spec Channel
uint16_t data[SPEC_CHANNELS];

void setup(){

  //Set desired pins to OUTPUT
  pinMode(SPEC_CLK, OUTPUT);
  pinMode(SPEC_ST, OUTPUT);

  digitalWrite(SPEC_CLK, HIGH); // Set SPEC_CLK High
  digitalWrite(SPEC_ST, LOW); // Set SPEC_ST Low

  Serial.begin(9600); // Baud Rate set to 9600

}

/*
 * This functions reads spectrometer data from SPEC_VIDEO
 * Look at the Timing Chart in the Datasheet for more info
 */
void readSpectrometer(){

  int delayTime = 1; // delay time

  // Start clock cycle and set start pulse to signal start
  digitalWrite(SPEC_CLK, LOW);
  delayMicroseconds(delayTime);
  digitalWrite(SPEC_CLK, HIGH);
  delayMicroseconds(delayTime);
  digitalWrite(SPEC_CLK, LOW);
  digitalWrite(SPEC_ST, HIGH);
  delayMicroseconds(delayTime);

  //Sample for a period of time
  for(int i = 0; i < 3000; i++){

      digitalWrite(SPEC_CLK, HIGH);
      delayMicroseconds(delayTime);
      digitalWrite(SPEC_CLK, LOW);
      delayMicroseconds(delayTime); 

  }

  //Set SPEC_ST to low
  digitalWrite(SPEC_ST, LOW);

  //Sample for a period of time
  for(int i = 0; i < 85; i++){

      digitalWrite(SPEC_CLK, HIGH);
      delayMicroseconds(delayTime);
      digitalWrite(SPEC_CLK, LOW);
      delayMicroseconds(delayTime); 

  }

  //One more clock pulse before the actual read
  digitalWrite(SPEC_CLK, HIGH);
  delayMicroseconds(delayTime);
  digitalWrite(SPEC_CLK, LOW);
  delayMicroseconds(delayTime);

  //Read from SPEC_VIDEO
  for(int i = 0; i < SPEC_CHANNELS; i++){

      data[i] = analogRead(SPEC_VIDEO);

      digitalWrite(SPEC_CLK, HIGH);
      delayMicroseconds(delayTime);
      digitalWrite(SPEC_CLK, LOW);
      delayMicroseconds(delayTime);

  }

  //Set SPEC_ST to high
  //digitalWrite(SPEC_ST, HIGH);

  //Sample for a small amount of time
  for(int i = 0; i < 7; i++){

      digitalWrite(SPEC_CLK, HIGH);
      delayMicroseconds(delayTime);
      digitalWrite(SPEC_CLK, LOW);
      delayMicroseconds(delayTime);

  }

  digitalWrite(SPEC_CLK, HIGH);
  delayMicroseconds(delayTime);

}

/*
 * The function below prints out data to the terminal or 
 * processing plot
 */
void printData(){

  for (int i = 0; i < SPEC_CHANNELS; i++){
    Serial.print(data[i]);
    Serial.print(',');

  }

  Serial.print("\n");
}

void loop(){

  readSpectrometer();
  printData();
  delay(1000);  

}

Jens Meder Jens Meder · Accepted Answer · 2017-03-15T13:30:49

It is a bit hard to determine what exactly causes your problem without knowing the exact sensor specifications. I can see at least to possible error sources:

The Trinket uses a 8 MHz oscillator vs. a 16MHz oscillator on the Arduino Uno.
The Trinket is available as 5V and 3.3V Logic Level version. In case you have the 3.3V version it might not be able to provide compatible levels for your sensor.

Hope that helps.

Serial data changes when using Arduino Pro Trinket vs. Uno

1 Answers