Error u8g was not declared in this scope

Arduino programming is an open-source and simple stage that arranges the Arduino board into working with a particular goal in mind. An Arduino code is written in C++ yet with extra capacities and strategies. An Arduino is an equipment and programming stage broadly utilised in hardware.

In this article, we go through three quick fixes for the error ‘was not declared in this scope’.

Also read: How to solve the Tower of Hanoi problem using Python?

What does the error mean?

Every programming language has a concept of Scope. Scope tells us where a specific variable, constant or function is accessible and usable. It refers to the area of code a statement, block, or name. The scope of an entity determines where that entity is usable in other parts of the program. The scope of a block determines where that block can be used in other blocks, and the scope of a name determines where that name can be used in other names.

There are two types of scope in programming languages: local and global. Local scope refers to the identifiers and symbols visible inside a block of code. Global scope, on the other hand, refers to the identifiers and symbols visible outside a block of code.

The error ‘was not declared in this scope’ generally occurs when a variable or function is not accessible to its call. A global variable in Arduino is the variable that is declared outside any function, including the setup() and loop() functions. Any variable declared inside a function or loop has restrictive access and is a local variable.

If any other function calls a local variable, it gives an error. To call any variable or function in any other function, including the setup() and loop() function, it should be declared as a global variable.

Also read: How to stop an Arduino program?

There are the quick fixes for the Arduino error: was not declared in the scope.

Declare the variable

Before assigning a value to the variable, make sure to define it. There are 16 data types commonly used in Arduino coding. Each data type expresses the nature of the value assigned to it. If the data type and value doesn’t match, an error arises. Also, if a variable is assigned any value without its declaration or data type, the error occurs.

Always ensure to declare the variable before the assignment. There are two ways to do this.

There are three variables in the above example – num1, num2 and num3. The variable num1 has been declared separately and assigned to a data type corresponding value in the loop. The variable num2 has been declared and assigned in the same line of code. The variable num3, on the other hand, has directly been assigned a value without its declaration. This causes the error, as shown above.

Other details

There may be errors arising even after proper declaration and assignment of the variable. This may be due to incorrect or absence of the closing brackets, semicolons or improper declaration of functions. Ensure proper use of syntax when defining loops and functions. Every opening in curly brace must be accounted for and closed. Extra closing braces also cause errors. Alongside, semicolons hold their importance. A semicolon missed can cause the entire program to go haywire.

Library folder

Many times, variables call or use functions that require importing a few specific libraries.

In the example above, the variable num calls the square root function – sqrt() from the maths library of Arduino. If we call a function without including its library first, an error occurs. There are multiple inbuilt and standard libraries in Arduino, while a few special libraries must be included separately.

Also read: What is ‘does not name a type’ in Arduino: 2 Fixes.

Here we go, I shall try again:

I am using Dev C++ Version 2, June 1991 on Windows XP

I am teaching myself to program a graphic lcd. Trying to compile another person’s C program. ( http://perso.orange.fr/rs-rey/electronic_ressources/Ressources/8051/GraphicLCD/GraphicLCD.htm ) I don’t understand why I don’t have a header file that declares variables like U8,U32,sfr,sbit already, if that is what needs to be done. And I don’t know how to fix this problem.

Ex: this is not the program, but bits and pieces of it. The program is too long to put in here. Each «stanza» per say, is one of the parts that gives me errors. I cannot create a simple program with these examples because I don’t understand how it works first.

void GLCD_LcdInit();
void GLCD_ClearScreen ();
void GLCD_DisplayPicture (U8);
void GLCD_Locate (U8, U8);
void GLCD_Rectangle (U8, U8, U8, U8);
void GLCD_Printf (U8, FONT_DEF*);
void GLCD_DisplayValue (U32, U8, U8) ;
void GLCD_Circle(U8, U8, U8);

/ BYTE Registers /
sfr P0 = 0x80;
sfr P1 = 0x90;
sfr P2 = 0xA0;
sfr P3 = 0xB0;
sfr PSW = 0xD0;
sfr ACC = 0xE0;
sfr B = 0xF0;
sfr SP = 0x81;
sfr DPL = 0x82;
sfr DPH = 0x83;
sfr PCON = 0x87;
sfr TCON = 0x88;
sfr TMOD = 0x89;
sfr TL0 = 0x8A;
sfr TL1 = 0x8B;
sfr TH0 = 0x8C;
sfr TH1 = 0x8D;

/ BIT Registers /
/ PSW /
sbit CY = PSW^7;
sbit AC = PSW^6;
sbit F0 = PSW^5;
sbit RS1 = PSW^4;
sbit RS0 = PSW^3;
sbit OV = PSW^2;
sbit P = PSW^0;

/ TCON /
sbit TF1 = TCON^7;
sbit TR1 = TCON^6;
sbit TF0 = TCON^5;
sbit TR0 = TCON^4;
sbit IE1 = TCON^3;

these are the compile errors I’m getting:

Compiler: Default compiler
Executing gcc.exe…
gcc.exe «C:Documents and SettingsElinDesktopBible CompGLCD.C» -o «C:Documents and SettingsElinDesktopBible CompGLCD.exe» -I»C:Dev-Cppinclude» -L»C:Dev-Cpplib»
In file included from C:Documents and SettingsElinDesktopBible CompGLCD.C:33:
C:Documents and SettingsElinDesktopBible Comp/reg51f.h:13: error: `sfr’ does not name a type

C:Documents and SettingsElinDesktopBible Comp/reg51f.h:51: error: `sfr’ does not name a type

C:Documents and SettingsElinDesktopBible Comp/reg51f.h:70: error: `sbit’ does not name a type

C:Documents and SettingsElinDesktopBible Comp/reg51f.h:109: error: `sbit’ does not name a type

In file included from C:Documents and SettingsElinDesktopBible CompGLCD.C:37:
C:/Dev-Cpp/include/font.h:31: error: U8' does not name a type
C:/Dev-Cpp/include/font.h:32: error:U8′ does not name a type
C:/Dev-Cpp/include/font.h:33: error: ISO C++ forbids declaration of U8' with no type
C:/Dev-Cpp/include/font.h:33: error: expected;’ before ‘*’ token
C:/Dev-Cpp/include/font.h:36: error: code' does not name a type
In file included from C:Documents and SettingsElinDesktopBible CompGLCD.C:38:
C:/Dev-Cpp/include/glcd.h:30: error: variable or fieldGLCD_DisplayPicture’ declared void
C:/Dev-Cpp/include/glcd.h:30: error: U8' was not declared in this scope
C:/Dev-Cpp/include/glcd.h:30: error: expected primary-expression before ')' token
C:/Dev-Cpp/include/glcd.h:31: error: variable or fieldGLCD_Locate’ declared void
C:/Dev-Cpp/include/glcd.h:31: error: U8' was not declared in this scope
C:/Dev-Cpp/include/glcd.h:31: error: initializer expression list treated as compound expression
C:/Dev-Cpp/include/glcd.h:32: error: variable or fieldGLCD_Rectangle’ declared void
C:/Dev-Cpp/include/glcd.h:32: error: U8' was not declared in this scope
C:/Dev-Cpp/include/glcd.h:32: error: initializer expression list treated as compound expression
C:/Dev-Cpp/include/glcd.h:33: error: variable or fieldGLCD_Printf’ declared void
C:/Dev-Cpp/include/glcd.h:33: error: U8' was not declared in this scope
C:/Dev-Cpp/include/glcd.h:33: error: expected primary-expression before ',' token
C:/Dev-Cpp/include/glcd.h:33: error: expected primary-expression before '*' token
C:/Dev-Cpp/include/glcd.h:33: error: expected primary-expression before ')' token
C:/Dev-Cpp/include/glcd.h:33: error: initializer expression list treated as compound expression
C:/Dev-Cpp/include/glcd.h:34: error: variable or fieldGLCD_DisplayValue’ declared void
C:/Dev-Cpp/include/glcd.h:34: error: U32' was not declared in this scope
C:/Dev-Cpp/include/glcd.h:34: error:U8′ was not declared in this scope
C:/Dev-Cpp/include/glcd.h:34: error: initializer expression list treated as compound expression
C:/Dev-Cpp/include/glcd.h:35: error: variable or field GLCD_Circle' declared void
C:/Dev-Cpp/include/glcd.h:35: error:U8′ was not declared in this scope
C:/Dev-Cpp/include/glcd.h:35: error: U8' was not declared in this scope
C:/Dev-Cpp/include/glcd.h:35: error: initializer expression list treated as compound expression
C:Documents and SettingsElinDesktopBible CompGLCD.C:43: error: variable or fieldLcdSelectSide’ declared void
C:Documents and SettingsElinDesktopBible CompGLCD.C:43: error: U8' was not declared in this scope
C:Documents and SettingsElinDesktopBible CompGLCD.C:44: error: variable or fieldLcdDataWrite’ declared void
C:Documents and SettingsElinDesktopBible CompGLCD.C:44: error: U8' was not declared in this scope
C:Documents and SettingsElinDesktopBible CompGLCD.C:45: error: variable or fieldLcdInstructionWrite’ declared void
C:Documents and SettingsElinDesktopBible CompGLCD.C:45: error: U8' was not declared in this scope
C:Documents and SettingsElinDesktopBible CompGLCD.C:46: error:U8′ does not name a type
C:Documents and SettingsElinDesktopBible CompGLCD.C:47: error: variable or field LcdSetDot' declared void
C:Documents and SettingsElinDesktopBible CompGLCD.C:47: error:U8′ was not declared in this scope
C:Documents and SettingsElinDesktopBible CompGLCD.C:47: error: U8' was not declared in this scope
C:Documents and SettingsElinDesktopBible CompGLCD.C:47: error: initializer expression list treated as compound expression
C:Documents and SettingsElinDesktopBible CompGLCD.C:49: error: variable or fieldLcdDelay’ declared void
C:Documents and SettingsElinDesktopBible CompGLCD.C:49: error: U32' was not declared in this scope
C:Documents and SettingsElinDesktopBible CompGLCD.C:50: error: variable or fieldLcdPutchar’ declared void
C:Documents and SettingsElinDesktopBible CompGLCD.C:50: error: U8' was not declared in this scope
C:Documents and SettingsElinDesktopBible CompGLCD.C:50: error: expected primary-expression before '*' token
C:Documents and SettingsElinDesktopBible CompGLCD.C:50: error: expected primary-expression before ')' token
C:Documents and SettingsElinDesktopBible CompGLCD.C:50: error: initializer expression list treated as compound expression
C:Documents and SettingsElinDesktopBible CompGLCD.C:53: error:xdata’ does not name a type
C:Documents and SettingsElinDesktopBible CompGLCD.C:63: error: variable or field LcdDelay' declared void
C:Documents and SettingsElinDesktopBible CompGLCD.C:63: error: redefinition ofint LcdDelay’
C:Documents and SettingsElinDesktopBible CompGLCD.C:49: error: int LcdDelay' previously defined here
C:Documents and SettingsElinDesktopBible CompGLCD.C:63: error:U32′ was not declared in this scope
C:Documents and SettingsElinDesktopBible CompGLCD.C:64: error: expected ,' or;’ before ‘{‘ token
C:Documents and SettingsElinDesktopBible CompGLCD.C: In function void GLCD_LcdInit()':
C:Documents and SettingsElinDesktopBible CompGLCD.C:75: error:P2′ undeclared (first use this function)
C:Documents and SettingsElinDesktopBible CompGLCD.C:75: error: (Each undeclared identifier is reported only once for each function it appears in.)
C:Documents and SettingsElinDesktopBible CompGLCD.C:76: error: P0_0' undeclared (first use this function)
C:Documents and SettingsElinDesktopBible CompGLCD.C:77: error:P0_1′ undeclared (first use this function)
C:Documents and SettingsElinDesktopBible CompGLCD.C:78: error: P0_2' undeclared (first use this function)
C:Documents and SettingsElinDesktopBible CompGLCD.C:79: error:P0_3′ undeclared (first use this function)
C:Documents and SettingsElinDesktopBible CompGLCD.C:80: error: P0_4' undeclared (first use this function)
C:Documents and SettingsElinDesktopBible CompGLCD.C:82: error:P0_5′ undeclared (first use this function)
C:Documents and SettingsElinDesktopBible CompGLCD.C:83: error: LcdDelay' cannot be used as a function
C:Documents and SettingsElinDesktopBible CompGLCD.C:85: error:LcdDelay’ cannot be used as a function
C:Documents and SettingsElinDesktopBible CompGLCD.C:88: error: LcdSelectSide' cannot be used as a function
C:Documents and SettingsElinDesktopBible CompGLCD.C:89: error:LcdInstructionWrite’ cannot be used as a function
C:Documents and SettingsElinDesktopBible CompGLCD.C:90: error: LcdInstructionWrite' cannot be used as a function
C:Documents and SettingsElinDesktopBible CompGLCD.C:91: error:LcdInstructionWrite’ cannot be used as a function
C:Documents and SettingsElinDesktopBible CompGLCD.C:92: error: LcdInstructionWrite' cannot be used as a function
C:Documents and SettingsElinDesktopBible CompGLCD.C:93: error:LcdInstructionWrite’ cannot be used as a function
C:Documents and SettingsElinDesktopBible CompGLCD.C:95: error: LcdSelectSide' cannot be used as a function
C:Documents and SettingsElinDesktopBible CompGLCD.C:96: error:LcdInstructionWrite’ cannot be used as a function
C:Documents and SettingsElinDesktopBible CompGLCD.C:97: error: LcdInstructionWrite' cannot be used as a function
C:Documents and SettingsElinDesktopBible CompGLCD.C:98: error:LcdInstructionWrite’ cannot be used as a function
C:Documents and SettingsElinDesktopBible CompGLCD.C:99: error: LcdInstructionWrite' cannot be used as a function
C:Documents and SettingsElinDesktopBible CompGLCD.C:100: error:LcdInstructionWrite’ cannot be used as a function

C:Documents and SettingsElinDesktopBible CompGLCD.C: At global scope:
C:Documents and SettingsElinDesktopBible CompGLCD.C:110: error: variable or field LcdSelectSide' declared void
C:Documents and SettingsElinDesktopBible CompGLCD.C:110: error: redefinition ofint LcdSelectSide’
C:Documents and SettingsElinDesktopBible CompGLCD.C:43: error: int LcdSelectSide' previously defined here
C:Documents and SettingsElinDesktopBible CompGLCD.C:110: error:U8′ was not declared in this scope
C:Documents and SettingsElinDesktopBible CompGLCD.C:111: error: expected ,' or;’ before ‘{‘ token
C:Documents and SettingsElinDesktopBible CompGLCD.C:141: error: variable or field LcdDataWrite' declared void
C:Documents and SettingsElinDesktopBible CompGLCD.C:141: error: redefinition ofint LcdDataWrite’

C:Documents and SettingsElinDesktopBible CompGLCD.C:44: error: `int LcdDataWrite’ previously defined here

C:Documents and SettingsElinDesktopBible CompGLCD.C:141: error: U8' was not declared in this scope
C:Documents and SettingsElinDesktopBible CompGLCD.C:142: error: expected,’ or ;' before '{' token
C:Documents and SettingsElinDesktopBible CompGLCD.C:159: error: variable or fieldLcdInstructionWrite’ declared void
C:Documents and SettingsElinDesktopBible CompGLCD.C:159: error: redefinition of int LcdInstructionWrite'
C:Documents and SettingsElinDesktopBible CompGLCD.C:45: error:int LcdInstructionWrite’ previously defined here
C:Documents and SettingsElinDesktopBible CompGLCD.C:159: error: U8' was not declared in this scope
C:Documents and SettingsElinDesktopBible CompGLCD.C:160: error: expected,’ or ;' before '{' token
C:Documents and SettingsElinDesktopBible CompGLCD.C:176: error:U8′ does not name a type
C:Documents and SettingsElinDesktopBible CompGLCD.C: In function void LcdWaitBusy()':
C:Documents and SettingsElinDesktopBible CompGLCD.C:197: error:P2′ undeclared (first use this function)
C:Documents and SettingsElinDesktopBible CompGLCD.C:199: error: P0_0' undeclared (first use this function)
C:Documents and SettingsElinDesktopBible CompGLCD.C:200: error:P0_1′ undeclared (first use this function)
C:Documents and SettingsElinDesktopBible CompGLCD.C:202: error: `P0_2′ undeclared (first use this function)

C:Documents and SettingsElinDesktopBible CompGLCD.C:203: error: `LcdDelay’ cannot be used as a function

C:Documents and SettingsElinDesktopBible CompGLCD.C: In function void GLCD_ClearScreen()':
C:Documents and SettingsElinDesktopBible CompGLCD.C:216: error:xdata’ undeclared (first use this function)
C:Documents and SettingsElinDesktopBible CompGLCD.C:216: error: expected ;' before "U8"
C:Documents and SettingsElinDesktopBible CompGLCD.C:217: error: expected;’ before «U8»
C:Documents and SettingsElinDesktopBible CompGLCD.C:220: error: u8Page' undeclared (first use this function)
C:Documents and SettingsElinDesktopBible CompGLCD.C:222: error:LcdSelectSide’ cannot be used as a function
C:Documents and SettingsElinDesktopBible CompGLCD.C:223: error: LcdInstructionWrite' cannot be used as a function
C:Documents and SettingsElinDesktopBible CompGLCD.C:224: error:LcdInstructionWrite’ cannot be used as a function
C:Documents and SettingsElinDesktopBible CompGLCD.C:227: error: u8Column' undeclared (first use this function)
C:Documents and SettingsElinDesktopBible CompGLCD.C:231: error:LcdSelectSide’ cannot be used as a function
C:Documents and SettingsElinDesktopBible CompGLCD.C:232: error: LcdInstructionWrite' cannot be used as a function
C:Documents and SettingsElinDesktopBible CompGLCD.C:233: error:LcdInstructionWrite’ cannot be used as a function
C:Documents and SettingsElinDesktopBible CompGLCD.C:235: error: LcdDataWrite' cannot be used as a function
C:Documents and SettingsElinDesktopBible CompGLCD.C: At global scope:
C:Documents and SettingsElinDesktopBible CompGLCD.C:245: error: variable or fieldGLCD_DisplayPicture’ declared void
C:Documents and SettingsElinDesktopBible CompGLCD.C:245: error: redefinition of int GLCD_DisplayPicture'
C:/Dev-Cpp/include/glcd.h:30: error:int GLCD_DisplayPicture’ previously defined here
C:Documents and SettingsElinDesktopBible CompGLCD.C:245: error: U8' was not declared in this scope
C:Documents and SettingsElinDesktopBible CompGLCD.C:245: error:au8PictureData’ was not declared in this scope
C:Documents and SettingsElinDesktopBible CompGLCD.C:246: error: expected ,' or;’ before ‘{‘ token
C:Documents and SettingsElinDesktopBible CompGLCD.C:275: error: variable or field LcdSetDot' declared void
C:Documents and SettingsElinDesktopBible CompGLCD.C:275: error: redefinition ofint LcdSetDot’
C:Documents and SettingsElinDesktopBible CompGLCD.C:47: error: int LcdSetDot' previously defined here
C:Documents and SettingsElinDesktopBible CompGLCD.C:275: error:U8′ was not declared in this scope

C:Documents and SettingsElinDesktopBible CompGLCD.C:276: error: expected ,' or;’ before ‘{‘ token
C:Documents and SettingsElinDesktopBible CompGLCD.C:318: error: variable or field LcdPutchar' declared void
C:Documents and SettingsElinDesktopBible CompGLCD.C:318: error: redefinition ofint LcdPutchar’
C:Documents and SettingsElinDesktopBible CompGLCD.C:50: error: `int LcdPutchar’ previously defined here

C:Documents and SettingsElinDesktopBible CompGLCD.C:318: error: U8' was not declared in this scope
C:Documents and SettingsElinDesktopBible CompGLCD.C:318: error: expected primary-expression before '*' token
C:Documents and SettingsElinDesktopBible CompGLCD.C:318: error:toto’ was not declared in this scope
C:Documents and SettingsElinDesktopBible CompGLCD.C:319: error: expected ,' or;’ before ‘{‘ token
C:Documents and SettingsElinDesktopBible CompGLCD.C:399: error: variable or field GLCD_Printf' declared void
C:Documents and SettingsElinDesktopBible CompGLCD.C:399: error: redefinition ofint GLCD_Printf’

C:/Dev-Cpp/include/glcd.h:33: error: `int GLCD_Printf’ previously defined here

C:Documents and SettingsElinDesktopBible CompGLCD.C:399: error: U8' was not declared in this scope
C:Documents and SettingsElinDesktopBible CompGLCD.C:399: error:au8Text’ was not declared in this scope
C:Documents and SettingsElinDesktopBible CompGLCD.C:399: error: expected primary-expression before ‘*’ token
C:Documents and SettingsElinDesktopBible CompGLCD.C:399: error: toto' was not declared in this scope
C:Documents and SettingsElinDesktopBible CompGLCD.C:400: error: expected,’ or ;' before '{' token
C:Documents and SettingsElinDesktopBible CompGLCD.C:414: error: variable or fieldGLCD_Locate’ declared void
C:Documents and SettingsElinDesktopBible CompGLCD.C:414: error: redefinition of int GLCD_Locate'
C:/Dev-Cpp/include/glcd.h:31: error:int GLCD_Locate’ previously defined here
C:Documents and SettingsElinDesktopBible CompGLCD.C:414: error: `U8′ was not declared in this scope

C:Documents and SettingsElinDesktopBible CompGLCD.C:415: error: expected ,' or;’ before ‘{‘ token
C:Documents and SettingsElinDesktopBible CompGLCD.C:429: error: variable or field GLCD_DisplayValue' declared void
C:Documents and SettingsElinDesktopBible CompGLCD.C:429: error: redefinition ofint GLCD_DisplayValue’
C:/Dev-Cpp/include/glcd.h:34: error: int GLCD_DisplayValue' previously defined here
C:Documents and SettingsElinDesktopBible CompGLCD.C:429: error:U32′ was not declared in this scope
C:Documents and SettingsElinDesktopBible CompGLCD.C:429: error: `U8′ was not declared in this scope

C:Documents and SettingsElinDesktopBible CompGLCD.C:430: error: expected ,' or;’ before ‘{‘ token
C:Documents and SettingsElinDesktopBible CompGLCD.C:473: error: variable or field GLCD_Rectangle' declared void
C:Documents and SettingsElinDesktopBible CompGLCD.C:473: error: redefinition ofint GLCD_Rectangle’
C:/Dev-Cpp/include/glcd.h:32: error: int GLCD_Rectangle' previously defined here
C:Documents and SettingsElinDesktopBible CompGLCD.C:473: error:U8′ was not declared in this scope

C:Documents and SettingsElinDesktopBible CompGLCD.C:474: error: expected ,' or;’ before ‘{‘ token
C:Documents and SettingsElinDesktopBible CompGLCD.C:499: error: variable or field GLCD_Circle' declared void
C:Documents and SettingsElinDesktopBible CompGLCD.C:499: error: redefinition ofint GLCD_Circle’
C:/Dev-Cpp/include/glcd.h:35: error: int GLCD_Circle' previously defined here
C:Documents and SettingsElinDesktopBible CompGLCD.C:499: error:U8′ was not declared in this scope

C:Documents and SettingsElinDesktopBible CompGLCD.C:500: error: expected ,' or;’ before ‘{‘ token

Execution terminated

sorry if it is too long…