struct name does not name a type

Question

I see there are a couple of Q&A in this topic but I still can't find the clue to my issue. I must admit I am pretty new to c++, so this might be the root cause.

Ok, so I am trying to declare a new type like :

struct measurement_t
{
  int sensorID;
  int sensorData;
  measurement_t(int ID, int Data)
  {
    sensorID = ID;
    sensorData = Data;
  }
};

and my project contains a method, that should return this type of data:

measurement_t getLightSensorData()
{
    ...
}

when I try to compile the code I got error : error: 'measurement_t' does not name a type

What I also find very strange is that the error line the compiler reports is the line number of the first #define statement at the very beginning of the code :

#define CE_PIN  7

If I simply change the method to void, the the project compiles (useless, though).

I also tried returning pointer by specifying measurement_t * as return type but the result is the same. Tried remove constructor from struct, same result again.

Can someone please help me to understand what the problem is here ?

The minimal version of the code that reproducing the same issue is:

struct measurement_t
{
  int sensorID;
  int sensorData;
  measurement_t(int ID, int Data)
  {
    sensorID = ID;
    sensorData = Data;
  }
};


measurement_t getLightSensorData()
{
  int sensorValue = 1;
  measurement_t m(1, sensorValue);
  return m;
}

For reference, this is intended to be an arduino sketch, and the full code is as below:

#include "RF24.h"
#include <SPI.h>
#include "printf.h"

#define CE_PIN  7
#define CS_PIN  8
#define LIGHTSENSOR_PIN A0

RF24 myRadio(CE_PIN, CS_PIN);
byte rxAddr[6] = { 0x0, 0x0, 0x0, 0x0, 0x0F };

unsigned long currentMillis;
unsigned long prevMillis;
unsigned long txIntervalMillis = 3000; // send once per second
unsigned long loopSleepMillis = 200;

struct measurement_t
{
  int sensorID;
  int sensorData;
  measurement_t(int ID, int Data)
  {
    sensorID = ID;
    sensorData = Data;
  }
};

// the setup routine runs once when you press reset:
void setup()
{
  Serial.println(">>> Initializing...");
  Serial.begin(115200);
  printf_begin();
  bool radioOk = myRadio.begin();  // Start up the physical nRF24L01 Radio
  if (radioOk) Serial.println("     Radio initialized");
  else Serial.println("     ERROR initializing radio !");
  myRadio.setChannel(120);  // Above most Wifi Channels
  myRadio.setPALevel(RF24_PA_HIGH);
  myRadio.setRetries(15, 15);
  myRadio.openWritingPipe(rxAddr); // Use the first entry in array 'addresses' (Only 1 right now)
  Serial.println("<<< Done initialization");
}

// the loop routine runs over and over again forever:
void loop()
{
  currentMillis = millis();
  if (currentMillis - prevMillis >= txIntervalMillis)
  {
    transmitData(getLightSensorData());
    prevMillis = millis();
  }
  delay(loopSleepMillis);
}

measurement_t getLightSensorData()
{
  int sensorValue = analogRead(LIGHTSENSOR_PIN);
  measurement_t m(1, sensorValue);
  return m;
}

void transmitData(measurement_t data)
{
  myRadio.stopListening();
  Serial.print("Transmitting data...");
  bool writeOK = myRadio.write(&data, sizeof(data));
  if (writeOK)
  {
    Serial.println("OK");
  }
  else
  {
    Serial.println(F("no response"));
    //myRadio.printDetails();
  }
}

Answer 1

You had to use

struct measurement_t getLightSensorData()
{
  int sensorValue = analogRead(LIGHTSENSOR_PIN);
  measurement_t m(1, sensorValue);
  return m;
}

You might have outdated version of Arduino IDE because on my IDE it compiled without the use of struct keyword.