Ambigous Error in sending data from Arduino to ThingSpeak

Hello Guys,

I am using Arduino to send data from liquid sensor to my ThingSpeak Channel. The totalMilliLitres and flowMilliLitres variables are unsigned long and unsigned int. The following error occurs during compilation:
call of overloaded 'writeField(long unsigned int&, int, unsigned int&, const char*&)' is ambiguous.

Following is my full code:

#if defined(ARDUINO_AVR_YUN)
    #include "YunClient.h"
    YunClient client;
#else
  #if defined(USE_WIFI101_SHIELD) || defined(ARDUINO_SAMD_MKR1000) || defined(ARDUINO_ARCH_ESP8266)
    // Use WiFi
    #ifdef ARDUINO_ARCH_ESP8266
      #include <ESP8266WiFi.h>
    #else
      #include <SPI.h>
      #include <WiFi101.h>
    #endif
    char ssid[] = "<>";    //  your network SSID (name) 
    char pass[] = "<>";   // your network password
    int status = WL_IDLE_STATUS;
    WiFiClient  client;
  #elif defined(USE_ETHERNET_SHIELD)
    // Use wired ethernet shield
    #include <SPI.h>
    #include <Ethernet.h>
    byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED};
    EthernetClient client;
  #endif
#endif

byte statusLed    = 13;

byte sensorInterrupt = 0;  // 0 = digital pin 2
byte sensorPin       = 3;

// The hall-effect flow sensor outputs approximately 7.5 pulses per second per
// litre/minute of flow.
float calibrationFactor = 7.0;

volatile byte pulseCount;  

float flowRate;
 float flowMilliLitres;
 unsigned int totalMilliLitres;

unsigned long oldTime;




/*
  *****************************************************************************************
  **** Visit https://www.thingspeak.com to sign up for a free account and create
  **** a channel.  The video tutorial http://community.thingspeak.com/tutorials/thingspeak-channels/ 
  **** has more information. You need to change this to your channel, and your write API key
  **** IF YOU SHARE YOUR CODE WITH OTHERS, MAKE SURE YOU REMOVE YOUR WRITE API KEY!!
  *****************************************************************************************/
#include "ThingSpeak.h"
unsigned long myChannelNumber = ;
const char * myWriteAPIKey = "";

void setup() {
  
  #ifdef ARDUINO_AVR_YUN
    Bridge.begin();
  #else   
    #if defined(ARDUINO_ARCH_ESP8266) || defined(USE_WIFI101_SHIELD) || defined(ARDUINO_SAMD_MKR1000)
      WiFi.begin(ssid, pass);
    #else
      Ethernet.begin(mac);
    #endif
  #endif

  ThingSpeak.begin(client);
  Serial.begin(38400);
   
  // Set up the status LED line as an output
  pinMode(statusLed, OUTPUT);
  digitalWrite(statusLed, HIGH);  // We have an active-low LED attached
  
  pinMode(sensorPin, INPUT);
  digitalWrite(sensorPin, HIGH);

  pulseCount        = 0;
  flowRate          = 0.0;
  flowMilliLitres   = 0;
  totalMilliLitres  = 0;
  oldTime           = 0;

  // The Hall-effect sensor is connected to pin 2 which uses interrupt 0.
  // Configured to trigger on a FALLING state change (transition from HIGH
  // state to LOW state)
  attachInterrupt(sensorInterrupt, pulseCounter, FALLING);
}


void loop() {
  
  
  // read the input on analog pin 0:
   if((millis() - oldTime) > 1000)    // Only process counters once per second
  { 
    // Disable the interrupt while calculating flow rate and sending the value to
    // the host
    detachInterrupt(sensorInterrupt);
        
    // Because this loop may not complete in exactly 1 second intervals we calculate
    // the number of milliseconds that have passed since the last execution and use
    // that to scale the output. We also apply the calibrationFactor to scale the output
    // based on the number of pulses per second per units of measure (litres/minute in
    // this case) coming from the sensor.
    flowRate = ((1000.0 / (millis() - oldTime)) * pulseCount) / calibrationFactor;
    
    // Note the time this processing pass was executed. Note that because we've
    // disabled interrupts the millis() function won't actually be incrementing right
    // at this point, but it will still return the value it was set to just before
    // interrupts went away.
    oldTime = millis();
    
    // Divide the flow rate in litres/minute by 60 to determine how many litres have
    // passed through the sensor in this 1 second interval, then multiply by 1000 to
    // convert to millilitres.
    flowMilliLitres = (flowRate / 60) * 1000;
    
    // Add the millilitres passed in this second to the cumulative total
    totalMilliLitres += flowMilliLitres;
    
    
      
    unsigned int frac;
     Serial.print("Flow rate: ");
    Serial.print(int(flowRate));  // Print the integer part of the variable
    Serial.print(".");             // Print the decimal point
    // Determine the fractional part. The 10 multiplier gives us 1 decimal place.
    frac = (flowRate - int(flowRate)) * 10;
    Serial.print(frac, DEC) ;      // Print the fractional part of the variable
    Serial.print("L/min");
    // Print the number of litres flowed in this second
    Serial.print("  Current Liquid Flowing: ");             // Output separator
    Serial.print(flowMilliLitres);
    Serial.print("mL/Sec");

    // Print the cumulative total of litres flowed since starting
    Serial.print("  Output Liquid Quantity: ");             // Output separator
    Serial.print(totalMilliLitres);
    Serial.println("mL"); 
   
   
    pulseCount = 0;
    ThingSpeak.writeField(myChannelNumber, 1, flowRate, myWriteAPIKey);
    
    ThingSpeak.writeField(myChannelNumber, 2, totalMilliLitres, myWriteAPIKey);
    delay(20000);
     
    // Enable the interrupt again now that we've finished sending output
    attachInterrupt(sensorInterrupt, pulseCounter, FALLING); 
   
     
   
   

    
  }
   
  
  
   
 
  // Write to ThingSpeak. There are up to 8 fields in a channel, allowing you to store up to 8 different
  // pieces of information in a channel.  Here, we write to field 1.
  
  
}
void pulseCounter()
{
  // Increment the pulse counter
  pulseCount++;
}

Can anyone help me in this?

Regards
Rushan

Well... the full error message should tell you what line of what file had the error and would probably include information about the two forms of 'writeField()' that it can't decide between. That information would be helpful. Try using the "Copy error messages" button and pasting the errors in a reply here, between code tags ('</>' icon above).

The full error is pasted below. Can you help me figure out where the problem lies?

Thank You.

Arduino: 1.8.3 (Windows Store 1.8.6.0) (Windows 10), Board: "Arduino Yún"

In file included from C:\Users\Rushan\Documents\Arduino\High-Flow-Wifi\High-Flow-Wifi.ino:2:0:

C:\Program Files\WindowsApps\ArduinoLLC.ArduinoIDE_1.8.6.0_x64__mdqgnx93n4wtt\libraries\Bridge\src/YunClient.h:24:2: warning: #warning "The use of YunClient is deprecated. Use BridgeClient instead!" [-Wcpp]

 #warning "The use of YunClient is deprecated. Use BridgeClient instead!"

  ^

C:\Users\Rushan\Documents\Arduino\High-Flow-Wifi\High-Flow-Wifi.ino: In function 'void loop()':

High-Flow-Wifi:129: error: call of overloaded 'writeField(long unsigned int&, int, long unsigned int&, const char*&)' is ambiguous

      ThingSpeak.writeField(myChannelNumber, 1, totalMilliLitres, myWriteAPIKey);

                                                                               ^

C:\Users\Rushan\Documents\Arduino\High-Flow-Wifi\High-Flow-Wifi.ino:129:79: note: candidates are:

In file included from C:\Users\Rushan\Documents\Arduino\High-Flow-Wifi\High-Flow-Wifi.ino:52:0:

C:\Users\Rushan\Documents\Arduino\libraries\ThingSpeak\src/ThingSpeak.h:230:6: note: int ThingSpeakClass::writeField(long unsigned int, unsigned int, int, const char*)

  int writeField(unsigned long channelNumber, unsigned int field, int value, const char * writeAPIKey)

      ^

C:\Users\Rushan\Documents\Arduino\libraries\ThingSpeak\src/ThingSpeak.h:253:6: note: int ThingSpeakClass::writeField(long unsigned int, unsigned int, long int, const char*)

  int writeField(unsigned long channelNumber, unsigned int field, long value, const char * writeAPIKey)

      ^

C:\Users\Rushan\Documents\Arduino\libraries\ThingSpeak\src/ThingSpeak.h:277:6: note: int ThingSpeakClass::writeField(long unsigned int, unsigned int, float, const char*)

  int writeField(unsigned long channelNumber, unsigned int field, float value, const char * writeAPIKey)

      ^

C:\Users\Rushan\Documents\Arduino\libraries\ThingSpeak\src/ThingSpeak.h:310:6: note: int ThingSpeakClass::writeField(long unsigned int, unsigned int, const char*, const char*) <near match>

  int writeField(unsigned long channelNumber, unsigned int field, const char * value, const char * writeAPIKey)

      ^

C:\Users\Rushan\Documents\Arduino\libraries\ThingSpeak\src/ThingSpeak.h:310:6: note:   no known conversion for argument 3 from 'long unsigned int' to 'const char*'

C:\Users\Rushan\Documents\Arduino\libraries\ThingSpeak\src/ThingSpeak.h:339:6: note: int ThingSpeakClass::writeField(long unsigned int, unsigned int, String, const char*) <near match>

  int writeField(unsigned long channelNumber, unsigned int field, String value, const char * writeAPIKey)

      ^

C:\Users\Rushan\Documents\Arduino\libraries\ThingSpeak\src/ThingSpeak.h:339:6: note:   no known conversion for argument 3 from 'long unsigned int' to 'String'

exit status 1
call of overloaded 'writeField(long unsigned int&, int, long unsigned int&, const char*&)' is ambiguous

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.

The error message says that the error is in Line 129 but in the sketch you posted above that line is 145. Did you make any changes between the sketch you published and the sketch that generated the errors?

In your published sketch the variable 'totalMilliLitres' is declared 'unsigned int' but the error says you are passing a 'long unsigned int reference'. Did you make any changes between the sketch you published and the sketch that generated the errors?

High-Flow-Wifi.ino: In function 'void loop()':
High-Flow-Wifi:129: error: call of overloaded 
'writeField(long unsigned int&, int, long unsigned int&, const char*&)' is ambiguous

      ThingSpeak.writeField(myChannelNumber, 1, totalMilliLitres, myWriteAPIKey);
      
High-Flow-Wifi.ino:129:79: note: candidates are:
ThingSpeak.h:230:6: note: int ThingSpeakClass::writeField(long unsigned int, unsigned int, int, const char*)
ThingSpeak.h:253:6: note: int ThingSpeakClass::writeField(long unsigned int, unsigned int, long int, const char*)
ThingSpeak.h:277:6: note: int ThingSpeakClass::writeField(long unsigned int, unsigned int, float, const char*)
ThingSpeak.h:310:6: note: int ThingSpeakClass::writeField(long unsigned int, unsigned int, const char*, const char*) <near match>
ThingSpeak.h:339:6: note: int ThingSpeakClass::writeField(long unsigned int, unsigned int, String, const char*) <near match>

It looks like writeField() only accepts 'int', 'long int', 'float', 'char *', and 'String' values. The compiler can't tell which of those you want your data type converted to. If you cast 'totalMilliLitres' as one of those the call would not be ambiguous anymore.

Sorry, I did change the unsigned long to int.
I think the problem you said is indeed the one. Can you give me a one liner on how can I cast totalMilliLitres to a string? I cant seem to work it out.

Thank You.

RushanArshad:
Sorry, I did change the unsigned long to int.

If you had done that it would have worked. For some reason the compiler is seeing it as a 'long unsigned int reference'. Perhaps you should post the actual sketch that caused the errors.

Okay here is the original sketch and the error message:

Sketch:

#if defined(ARDUINO_AVR_YUN)
    #include "YunClient.h"
    YunClient client;
#else
  #if defined(USE_WIFI101_SHIELD) || defined(ARDUINO_SAMD_MKR1000) || defined(ARDUINO_ARCH_ESP8266)
    // Use WiFi
    #ifdef ARDUINO_ARCH_ESP8266
      #include <ESP8266WiFi.h>
    #else
      #include <SPI.h>
      #include <WiFi101.h>
    #endif
    char ssid[] = "<>";    //  your network SSID (name) 
    char pass[] = "<>";   // your network password
    int status = WL_IDLE_STATUS;
    WiFiClient  client;
  #elif defined(USE_ETHERNET_SHIELD)
    // Use wired ethernet shield
    #include <SPI.h>
    #include <Ethernet.h>
    byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED};
    EthernetClient client;
  #endif
#endif

byte statusLed    = 13;

byte sensorInterrupt = 1;  // 0 = digital pin 2
byte sensorPin       = 3;

// The hall-effect flow sensor outputs approximately 7.5 pulses per second per
// litre/minute of flow.
float calibrationFactor = 7.0;

volatile byte pulseCount;  

float flowRate;
 unsigned int  flowMilliLitres;
  unsigned long totalMilliLitres;

unsigned long oldTime;




/*
  *****************************************************************************************
  **** Visit https://www.thingspeak.com to sign up for a free account and create
  **** a channel.  The video tutorial http://community.thingspeak.com/tutorials/thingspeak-channels/ 
  **** has more information. You need to change this to your channel, and your write API key
  **** IF YOU SHARE YOUR CODE WITH OTHERS, MAKE SURE YOU REMOVE YOUR WRITE API KEY!!
  *****************************************************************************************/
#include "ThingSpeak.h"
unsigned long myChannelNumber =;
const char * myWriteAPIKey = "";

void setup() {
  
  #ifdef ARDUINO_AVR_YUN
    Bridge.begin();
  #else   
    #if defined(ARDUINO_ARCH_ESP8266) || defined(USE_WIFI101_SHIELD) || defined(ARDUINO_SAMD_MKR1000)
      WiFi.begin(ssid, pass);
    #else
      Ethernet.begin(mac);
    #endif
  #endif

  ThingSpeak.begin(client);
  Serial.begin(38400);
   
  // Set up the status LED line as an output
  pinMode(statusLed, OUTPUT);
  digitalWrite(statusLed, HIGH);  // We have an active-low LED attached
  
  pinMode(sensorPin, INPUT);
  digitalWrite(sensorPin, HIGH);

  pulseCount        = 0;
  flowRate          = 0.0;
  flowMilliLitres   = 0;
  totalMilliLitres  = 0;
  oldTime           = 0;

  // The Hall-effect sensor is connected to pin 2 which uses interrupt 0.
  // Configured to trigger on a FALLING state change (transition from HIGH
  // state to LOW state)
  attachInterrupt(sensorInterrupt, pulseCounter, FALLING);
}


void loop() {
  
  
  // read the input on analog pin 0:
   if((millis() - oldTime) > 1000)    // Only process counters once per second
  { 
    // Disable the interrupt while calculating flow rate and sending the value to
    // the host
    detachInterrupt(sensorInterrupt);
        
    // Because this loop may not complete in exactly 1 second intervals we calculate
    // the number of milliseconds that have passed since the last execution and use
    // that to scale the output. We also apply the calibrationFactor to scale the output
    // based on the number of pulses per second per units of measure (litres/minute in
    // this case) coming from the sensor.
    flowRate = ((1000.0 / (millis() - oldTime)) * pulseCount) / calibrationFactor;
    
    // Note the time this processing pass was executed. Note that because we've
    // disabled interrupts the millis() function won't actually be incrementing right
    // at this point, but it will still return the value it was set to just before
    // interrupts went away.
    oldTime = millis();
    
    // Divide the flow rate in litres/minute by 60 to determine how many litres have
    // passed through the sensor in this 1 second interval, then multiply by 1000 to
    // convert to millilitres.
    flowMilliLitres = (flowRate / 60) * 1000;
    
    // Add the millilitres passed in this second to the cumulative total
    totalMilliLitres += flowMilliLitres;
    
    
      
    unsigned int frac;
                // Print the decimal point
    // Determine the fractional part. The 10 multiplier gives us 1 decimal place.
    frac = (flowRate - int(flowRate)) * 10;
     
   
   
    pulseCount = 0;
   
    
    ThingSpeak.writeField(myChannelNumber, 1, totalMilliLitres, myWriteAPIKey);
    delay(20000);
     
    // Enable the interrupt again now that we've finished sending output
    attachInterrupt(sensorInterrupt, pulseCounter, FALLING); 
   
     
   
   

    
  }
   
  
  
   
 
  // Write to ThingSpeak. There are up to 8 fields in a channel, allowing you to store up to 8 different
  // pieces of information in a channel.  Here, we write to field 1.
  
  
}
void pulseCounter()
{
  // Increment the pulse counter
  pulseCount++;
}

Error Message:

Arduino: 1.8.3 (Windows Store 1.8.6.0) (Windows 10), Board: "Arduino Yún"

In file included from C:\Users\Rushan\Documents\Arduino\newhigh-flow\newhigh-flow.ino:2:0:

C:\Program Files\WindowsApps\ArduinoLLC.ArduinoIDE_1.8.6.0_x64__mdqgnx93n4wtt\libraries\Bridge\src/YunClient.h:24:2: warning: #warning "The use of YunClient is deprecated. Use BridgeClient instead!" [-Wcpp]

 #warning "The use of YunClient is deprecated. Use BridgeClient instead!"

  ^

C:\Users\Rushan\Documents\Arduino\newhigh-flow\newhigh-flow.ino: In function 'void loop()':

newhigh-flow:135: error: call of overloaded 'writeField(long unsigned int&, int, long unsigned int&, const char*&)' is ambiguous

     ThingSpeak.writeField(myChannelNumber, 1, totalMilliLitres, myWriteAPIKey);

                                                                              ^

C:\Users\Rushan\Documents\Arduino\newhigh-flow\newhigh-flow.ino:135:78: note: candidates are:

In file included from C:\Users\Rushan\Documents\Arduino\newhigh-flow\newhigh-flow.ino:53:0:

C:\Users\Rushan\Documents\Arduino\libraries\ThingSpeak\src/ThingSpeak.h:230:6: note: int ThingSpeakClass::writeField(long unsigned int, unsigned int, int, const char*)

  int writeField(unsigned long channelNumber, unsigned int field, int value, const char * writeAPIKey)

      ^

C:\Users\Rushan\Documents\Arduino\libraries\ThingSpeak\src/ThingSpeak.h:253:6: note: int ThingSpeakClass::writeField(long unsigned int, unsigned int, long int, const char*)

  int writeField(unsigned long channelNumber, unsigned int field, long value, const char * writeAPIKey)

      ^

C:\Users\Rushan\Documents\Arduino\libraries\ThingSpeak\src/ThingSpeak.h:277:6: note: int ThingSpeakClass::writeField(long unsigned int, unsigned int, float, const char*)

  int writeField(unsigned long channelNumber, unsigned int field, float value, const char * writeAPIKey)

      ^

C:\Users\Rushan\Documents\Arduino\libraries\ThingSpeak\src/ThingSpeak.h:310:6: note: int ThingSpeakClass::writeField(long unsigned int, unsigned int, const char*, const char*) <near match>

  int writeField(unsigned long channelNumber, unsigned int field, const char * value, const char * writeAPIKey)

      ^

C:\Users\Rushan\Documents\Arduino\libraries\ThingSpeak\src/ThingSpeak.h:310:6: note:   no known conversion for argument 3 from 'long unsigned int' to 'const char*'

C:\Users\Rushan\Documents\Arduino\libraries\ThingSpeak\src/ThingSpeak.h:339:6: note: int ThingSpeakClass::writeField(long unsigned int, unsigned int, String, const char*) <near match>

  int writeField(unsigned long channelNumber, unsigned int field, String value, const char * writeAPIKey)

      ^

C:\Users\Rushan\Documents\Arduino\libraries\ThingSpeak\src/ThingSpeak.h:339:6: note:   no known conversion for argument 3 from 'long unsigned int' to 'String'

exit status 1
call of overloaded 'writeField(long unsigned int&, int, long unsigned int&, const char*&)' is ambiguous

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.

Can you give me a short example how can I cast totalMilliLitres to float or string?

Thank You

It should be sufficient to say:

     ThingSpeak.writeField(myChannelNumber, 1, (long) totalMilliLitres, myWriteAPIKey);

I'm still surprised that the compiler sees your 'unsigned long' as 'long unsigned int &'.

Yes thats surprising for me too.

Thanks for your reply.

Just one last question. If you have experience with ThingSpeak, will the data be sent to ThingSpeak channel if my laptop have been conencted to required wifi but arduino is sending data through serial port?

RushanArshad:
Just one last question. If you have experience with ThingSpeak, will the data be sent to ThingSpeak channel if my laptop have been conencted to required wifi but arduino is sending data through serial port?

I have no experience with Thingspeak.