I hope that you already go through our tutorial, Interfacing LCD with PIC Microcontroller – MPLAB XC8. HD44780 compatible controllers used in these LCDs allows us to define 8 custom characters in addition to the standard pre-programmed characters. In this tutorial we will learn, how to create custom characters on LCD using PIC Microcontroller and MPLAB XC8 compiler.

DDRAM, CGROM and CGRAM

CGROM – Character Generator ROM

This is the memory which holds 5×8 or 5×10 dot patterns of predefined characters in the LCD. It can generate 208 5×8 dot character patterns and 32 5×10 dot character patterns.

DDRAM – Display Data RAM

This is the memory which holds the character data which is currently displayed on the LCD screen. Its capacity is 80×8 bits, ie 80 characters.

CGRAM – Character Generator RAM

This memory works similar to CGROM but as this is a RAM we can modify its data any time. So we can store our custom character patterns in this memory through program. We can store up to eight 5×8 character dot patterns or four 5×10 character dot patterns in this memory.

Character Generation

Characters are displayed on the LCD using 5×8 or 5×10 dot matrix. Most of the commonly available displays uses 5×8 dot matrix. We can simply create a custom character by defining each pixel in the dot matrix. Here is an example of creating Ω symbol on 5×8 dot matrix.Project List – 871 PIC Microcontroller

For more detail: Custom Characters on LCD using PIC – MPLAB XC8

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