Why when I pull an EEPROM index the value returned is garbage?

Question

I have an array of colors for my tft screen:

const uint16_t colorTheme [] PROGMEM = {BLACK, WHITE, NAVY, CYAN, RED, GREEN, VERDEAQ, PINK, ORANGE, PURPLE, GRAY, YELLOW};

When I try to use colorTheme [EEPROM.read (2500)] I am returned with a value of any garbage, or a value of 0, and I checked it in read_eeprom and the value of EEPROM.read (2500) is equal to 4, and 4 in mine vector is cyan color, not black or 0 number, why does this go so wrong?

Answer 1

Your array is in PROGMEM, but you are accessing it as if it were in RAM.

You must use pgm_read_word() to access the data in your array.

pgm_read_word(&(colorTheme[EEPROM.read(x)]))

BTW - what Arduino board has more than 2kB of EEPROM?

• luke cross: Thanks, i'm using Atmega2560, he store.arduino.cc/usa/mega-2560-r3, your EEPROM is 4kb