PROGMEM and arrays: garbage

Projects Programming
1

I encounter problems with using stuff in PROGMEM flash memory. To make things easier to see I have written a small sketch which shows the problem.

const PROGMEM byte data[] = 
{ 
  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
};


void setup() 
{
  int i;
  byte displayInt;

  Serial.begin( 115200 );

  Serial.println( "Test" ); 

  for( i=0; i<8; i++ )
    Serial.println( pgm_read_byte( data[i] ), HEX );
  
  Serial.println( "------" ); 
  
  for( i=0; i<8; i++ )
    Serial.println( pgm_read_byte( data+i ), HEX );
}

void loop() 
{
}

The first loop produces garbage, the 2nd one correct values. Why?

2

data[nobbc][i][/nobbc] gets the element at index i. You need the address of the element at index i, so either &data[nobbc][i][/nobbc] or data[nobbc] + i[/nobbc].

Pieter