Noob alert : dtostrf problem

Projects Programming
1

Hi all

I am trying to get some code to output data using the VGA module from Strich Labs. My issue is around converting a float (analogue volt read from a temp sensor) to char that the VGA module can handle.

Code (obviously not my own work) below:

#include <Wire.h>
#include <MultiSerial.h>
#include <VGA.h>
#include <stdlib.h>


#define RES_X  640
#define RES_Y  480

VGA vgaInstance = VGA(0x4D);
char temperatureVGA;

int sensorPin = 5;
void setup()
{
  Serial.begin(115200);  
//  vgaInstance.begin();

  //vgaInstance.setResolution(RES_640x480);
  //vgaInstance.textBackgroundOpaque(1);  
  //vgaInstance.fillShapes(0);
  //vgaInstance.setFont(FONT_12x16);
  //vgaInstance.clearScreen();
}
 
 void loop()                    
{
  int reading = analogRead(sensorPin);  
 
 float voltage = reading * 5.0;
 voltage /= 1024.0; 
 
 // print out the readings
 Serial.print(voltage); Serial.println(" volts");
 float temperatureC = (voltage - 0.5) * 100 ;
 Serial.print(temperatureC); Serial.println(" degrees C");
 float temperatureF = (temperatureC * 9.0 / 5.0) + 32.0;
 Serial.print(temperatureF); Serial.println(" degrees F");
 dtostrf(temperatureC,0,2,temperatureVGA);
vgaInstance.drawGraphicsText("The coolant temperature is ",10,10,2,2,vgaInstance.generateColour(0,255,0));
vgaInstance.drawGraphicsText(temperatureVGA,10,10,2,2,vgaInstance.generateColour(0,255,0));
 
 delay(1000);                                     
}

Error on compile is

Test_VGA_Temp_1_2.cpp: In function 'void loop()':
Test_VGA_Temp_1_2:38: error: invalid conversion from 'char' to 'char*'
Test_VGA_Temp_1_2:38: error: initializing argument 4 of 'char* dtostrf(double, signed char, unsigned char, char*)'
Test_VGA_Temp_1_2.cpp:43: warning: deprecated conversion from string constant to 'char*'
Test_VGA_Temp_1_2:40: error: invalid conversion from 'char' to 'char*'
Test_VGA_Temp_1_2:40: error: initializing argument 1 of 'void VGA::drawGraphicsText(char*, short int, short int, byte, byte, PackedColour)'

Any advice much appreciated.

FYI this is for a monitor on a CNC machine, reading temp, flow rates etc.

Thanks

2

Hello, the problem is that your

char temperatureVGA;

is a single char, and, as it will be used to store more than one character, you need an array of chars:

char temperatureVGA[8];
3

You Sir, are a gentleman and a scholar.
Thank you.