In mass production situation, each finish products LCD driving voltage may have tolerance. LCD driver ICs internal reference voltage may contain small deviation, too. These add up, could make the final product LCD display contrast vary.
Topway LM240160D & LM240160G series LCM make use of Sitronix ST7529 on-chip EEPROM, to store a contrast adjustment value for better display.
It is recommended to call out that value during LCM start-up routine, as below:
//--------------- Call out EEPROM compensation ---------------
SdCmd(0x30); // select ext0 command set
SdCmd(0x07); SdData(0x19); // run ACK signal
SdCmd(0x31); // select ext1 command set
SdCmd(0xcd); SdData(0x00); delayms(100); // enable EEPROM function
SdCmd(0xfd); delayms(100); // call out the EEPROM value
SdCmd(0xcc); // finish EEPROM function
For start-up program routine, please refer to LM240160G sample code.
For ST7529 commands, please see ST7529 datasheet.