program error on write to lcd

Projects Programming
1

I am trying to display what comes in on serial. My code

#include "LCD12864RSPI.h"
#include "DFrobot_bmp.h"
#include "DFrobot_char.h"

#define AR_SIZE( a ) sizeof( a ) / sizeof( a[0] )
void setup()
{
  LCDA.initDriverPin(8,9,10); 
  LCDA.Initialise(); // INIT SCREEN  
  delay(100);
}
void loop()
{
  String msg;
  LCDA.CLEAR();//????
  delay(100);
  if (Serial.available() > 0)
  {
    while (Serial.available() > 0)
    {
      msg += char(Serial.read());
      if (msg = "/n")
       {
         LCDA.DisplayString(0,0,msg,16);
         break;
       }
    }  
  }  
  delay(500);
}

and error

LCD12864_test.ino: In function 'void loop()':
LCD12864_test:24: error: no matching function for call to 'LCD12864RSPI::DisplayString(int, int, String&, int)'
C:\Users\Jim\Documents\Arduino\libraries\LCD12864RSPI/LCD12864RSPI.h:29: note: candidates are: void LCD12864RSPI::DisplayString(int, int, unsigned char*, int)

I always have trouble with char arrays-strings
Jim

2

Maybe doing something like:

         LCDA.DisplayString(0,0,&msg,16);

can solve the problem. I never use String class so I'm not sure.

You can too remove the String class from your code and use regular C strings (using arrays of chars) that is what your compiler is trying to say to you:

note: candidates are: void LCD12864RSPI::DisplayString(int, int, unsigned char*, int)

when it says unsigned char*.

3

I don't have your libraries, but I can see several problems:

  1. using the String class is usually unnecessary. Better off with a char array.
  2. You never define the LCDA object, which means you can't call the CLEAR() method. Does
    LCD12864RSPI.h mean it is a Raspberry Pi library?
  3. Why the call to delay(100)?
  4. Since you're looking for the newline character ('\n'), use readBytesUntil() method. charsRead tells you how many
    characters were sent.
void loop()
{
 // String msg;                                Get rid of this, and use this instead...
  char msg[20];                      // I'm assuming the message is never more than 19 chars.
  int charsRead;

  LCDA.CLEAR();//????   // You have not defined a LCDA object anywhere. Does
  delay(100);
  if (Serial.available() > 0)   {
      charsRead = Serial.readBytesUntil('\n', msg, 19);  // we need room for the null character for strings
      msg[charsRead] = '\n';
      LCDA.DisplayString(0,0,msg,16);
  }  
  delay(500);
}
4

econjack:
(...)
2. You never define the LCDA object, which means you can't call the CLEAR() method. Does
LCD12864RSPI.h mean it is a Raspberry Pi library?
(...)

These are not issues. "LCD12864RSPI.h" means LCD12864R - SPI, and form the sample on this page, the definition is OK.

5

@luisilva: As I said, I did not have the library and had no info on it. Personally, I absolutely abhor header files that contain data definitions for class objects. I would also be surprised if the call to the LCDA.CLEAR() method worked since it is defined in the header file in lower case letters.

6

econjack:
I don't have your libraries, but I can see several problems:

  1. using the String class is usually unnecessary. Better off with a char array.
  2. You never define the LCDA object, which means you can't call the CLEAR() method. Does
    LCD12864RSPI.h mean it is a Raspberry Pi library?
  3. Why the call to delay(100)?
  4. Since you're looking for the newline character ('\n'), use readBytesUntil() method. charsRead tells you how many
    characters were sent.

1 you are probably totally right
2 yes
3 it was in the sample code. I thought it might be for a reason, so I left it in.
4 right
I will try you sample.
Jim

7

I been away on business, just got back, and started trying your code.
Current code

#include "LCD12864RSPI.h"
#include "DFrobot_bmp.h"
#include "DFrobot_char.h"

#define AR_SIZE( a ) sizeof( a ) / sizeof( a[0] )
unsigned char tT[]="ST7920 LCD12864 ";// 

void setup()
{
  LCDA.initDriverPin(2,7,10); 
  LCDA.Initialise(); // INIT SCREEN  
  delay(100);
  LCDA.DrawFullScreen(logo);//LOGO
  delay(5000);
  Serial.begin(9600);
}

void loop()
{
   char msg[20];                     
  int charsRead;
  LCDA.CLEAR();
  delay(100);
  if (Serial.available() > 0)   {
      charsRead = Serial.readBytesUntil('\n', msg, 19);  // we need room for the null character for strings
      msg[charsRead] = '\n';
//      LCDA.DisplayString(0,0,msg,16);
      LCDA.DisplayString(1,0,tT,16); 
  delay(500);
}
delay(5000);
}

Code as displayed does compile,and run correctly. Commented code does not compile. Error is

lcdtest.ino: In function 'void loop()':
lcdtest:28: error: invalid conversion from 'char*' to 'unsigned char*'
lcdtest:28: error: initializing argument 3 of 'void LCD12864RSPI::DisplayString(int, int, unsigned char*, int)'

I am afraid I just don't groc it when pointers are involved. I was a hardware person involved in very large power supplies(150 KV300A) before I retired.

Jim

8

Hi,

Try replacig your line by:

      LCDA.DisplayString(0,0,(unsigned char*) msg,16);