024EN Arduino Piano 4 - Software Data Structures in C/C++ - integer and pointers

Building an Arduino piano part 4 - software, data structures in C/C++ - integer numbers and pointers

In preparation for the actual software code, the data structures in C/C++ for signed and unsigned integers and the pointers are discussed in this part. The use of the asterisk (*) and the & character is explained. Finally, pointer arithmetic is discussed in detail.

0:00 introduction
0:22 content
0:48 int8_t, uint8_t, int16_t, uint16_t, int32_t, uint32_t
2:36 int8_t in detail
4:29 uint8_t in detail
4:50 value ranges for int8_t..int32_t, uint8_t..uint32_t
4:58 nibble and hex numbers
7:01 program code - general notes
7:47 output of the value ranges with the Arduino
10:01 pointers and their application
10:35 pointer in variable declaration
11:20 apply pointers
13:26 pointer - sample code on the Arduino
16:34 pointer arithmetic with pointer to 8-bit number
19:03 8-bit number pointer arithmetic on the Arduino
21:38 pointer arithmetic with pointer to 16-bit number
24:08 16-bit number pointer arithmetic on the Arduino
28:12 notes about the software in the video description
28:45 end



Software:
#include LOWERArduino.hBIGGER
#include LOWERstdint.hBIGGER

#define Stopp do {} while( true )

void setup()
{
} // setup

void OutIntHex( char Message[], int8_t Bytes, void *Number )
{
char IntToHex[16] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
uint8_t *N;
N = Number;
N = N + Bytes - 1;
Print( Message );
for (int8_t i = 0; i LOWER Bytes; i++)
{
Print(IntToHex[*N SHIFTR 4]);
Print(IntToHex[*N & 0x0F]);
N--;
}
Println();
} // OutIntHex

void OutInt8Hex(char Message[], int8_t Number)
{
OutIntHex(Message, 1, &Number);
} // OutInt8Hex

void OutInt16Hex(char Message[], int16_t Number)
{
OutIntHex(Message, 2, &Number);
} // OutInt16Hex

void OutInt32Hex(char Message[], int32_t Number)
{
OutIntHex(Message, 4, &Number);
} // OutInt32Hex

void DataSizeTest()
{
int8_t int8min = 0x80;
int8_t int8max = 0x7F;
uint8_t uint8max = 0xFF;
int16_t int16min = 0x8000;
int16_t int16max = 0x7FFF;
uint16_t uint16max = 0xFFFF;
int32_t int32min = 0x80000000;
int32_t int32max = 0x7FFFFFFF;
uint32_t uint32max = 0xFFFFFFFF;

Println( "DataSizeTest" );
Print( " int8_t min=" );
Println( int8min );
Print( " int8_t max= " );
Println( int8max );
Print( " uint8_t max= " );
Println( uint8max );
Print( " int16_t min=" );
Println( int16min );
Print( " int16_t max= " );
Println( int16max );
Print( "uint16_t max= " );
Println( uint16max );
Print( " int32_t min=" );
Println( int32min );
Print( " int32_t max= " );
Println( int32max );
Print( "uint32_t max= " );
Println( uint32max );
Stopp;
} // DataSizeTest

void PointerTest1()
{
int16_t A;
int16_t B;
int16_t *C;

Println("PointerTest1");
A = 0x2211;
OutInt16Hex(" A=", A);
C = &A;
OutInt16Hex(" C=", (uint16_t)C);
OutInt16Hex("*C=", *C);
B = *C;
OutInt16Hex(" B=", B);
*C = 0;
OutInt16Hex("*C=", *C);
OutInt16Hex(" A=", A);
Stopp;
} // PointerTest1

void PointerTest2()
{
int32_t A;
int8_t *C;

Println("PointerTest2");
A = 0x44332211;
OutInt32Hex(" A=", A);
C = (int8_t *)&A;
OutInt16Hex(" C=", (uint16_t)C);
OutInt8Hex("*C=", *C);
C = C + 1;
OutInt16Hex(" C=", (uint16_t)C);
OutInt8Hex("*C=", *C);
C = C + 1;
OutInt16Hex(" C=", (uint16_t)C);
OutInt8Hex("*C=", *C);
C = C + 1;
OutInt16Hex(" C=", (uint16_t)C);
OutInt8Hex("*C=", *C);
Stopp;
} // PointerTest2

void PointerTest3()
{
int32_t A;
int16_t *C;

Println("PointerTest3");
A = 0x44332211;
OutInt32Hex(" A=", A);
C = (int16_t *)&A;
OutInt16Hex(" C=", (uint16_t)C);
OutInt16Hex("*C=", *C);
C = C + 1;
OutInt16Hex(" C=", (uint16_t)C);
OutInt16Hex("*C=", *C);
Stopp;
} // PointerTest3

void loop()
{
DataSizeTest();
// PointerTest1();
// PointerTest2();
// PointerTest3();
} // loop