/*
  This project is used only for dictative purposes and
  was inspired by the video tutorial
  How a Character LCD works of the 8-Bit Guy Channel
  https://www.youtube.com/watch?v=hZRL8luuPb8

  1. Start the simulation
  2. Start the display
     dip-switch: 11110000 and press pushbutton enable
  3. CTRL + pushbutton RS
  4. Send commands & data
     See README.md or Description

  Note: ATtiny85 was used as a power supply only.
*/

int main(void)
{
  while (1)
    ; // It doesn't do anything, just not to give a compilation error. ;)
  return 0;
}


main.c

diagram.json

# How 16×2 LCDs work

### 16X2 LCD pinout diagram

| Pin	| Name |	Function                                                      |
| --- | ---- | -------------------------------------------------------------- |
|  1	| Gnd  | Ground (0V)                                                    |
|  2	| Vcc  | Supply voltage; 5V (4.7V – 5.3V)                               |
|  3	| Vo   | Contrast adjustment                                            |
|  4	| RS   | Selects command register when low, and data register when high |
|  5	| RW   | Low to write to the register; High to read from the register   |
|  6	| EN   | Sends data to data pins when a high to low pulse is given      |                       |
|  7	| DB0  | 8-bit data pins [DB0... DB7]                                   |
|  8	| DB1  |                                                                |
|  9	| DB2  |	                                                              |
| 10	| DB3  |	                                                              |
| 11	| DB4  |	                                                              |
| 12	| DB5  |	                                                              |
| 13	| DB6  | 	                                                              |
| 14	| DB7  |	                                                              |
| 15	| LED+ | Backlight VCC (5V)                                             |
| 16	| LED- | Backlight Ground (0V)                                          |

## Important command codes for LCD

## RS (Register select)
A 16X2 LCD has two registers, namely, command and data. The register select is used to switch from one register to other. RS=0 for command register, whereas RS=1 for data register.

***Command Register:*** 
The command register stores the command instructions given to the LCD.\
A command is an instruction given to LCD to do a predefined task. Examples like:

initializing it
* clearing its screen
* setting the cursor position
* controlling display etc.
* Processing for commands happens in the command register.

***Data Register:*** 
The data register stores the data to be displayed on the LCD.\
The data is the ASCII value of the character to be displayed on the LCD. When we send data to LCD it goes to the data register and is processed there. When RS=1, data register is selected.

## Important command codes for LCD

| No.	| 0x |	Command to LCD instruction Register     |
| --- | -- | ---------------------------------------- |
|  1	| 01 | Clear display screen                     |
|  2	| 02 | Return home                              |
|  3	| 04 | Decrement cursor (shift cursor to left)  |
|  4	| 06 | Increment cursor (shift cursor to right) |
|  5	| 05 | Shift display right                      |
|  6	| 07 | Shift display left                       |
|  7	| 08 |	Display off, cursor off                 |
|  8	| 0A |	Display off, cursor on                  |
|  9	| 0C |	Display on, cursor off                  |
| 10	| 0E |	Display on, cursor blinking             |
| 11	| 0F |	Display on, cursor blinking             |
| 12	| 10 |	Shift cursor position to left           |
| 13	| 14 | 	Shift cursor position to right          |
| 14	| 18 |	Shift the entire display to the left    |
| 15	| 1C |	Shift the entire display to the right   |
| 16	| 80 |	Force cursor to beginning ( 1st line)   |
| 17	| C0 |	Force cursor to beginning ( 2nd line)   |
| 18	| 38 |	2 lines and 5×7 matrix                  |

### Displaying Custom Characters on 16X2 LCD

Generating custom characters on LCD is not very hard.
It requires the knowledge about custom generated random access memory (CG-RAM) of LCD and the LCD chip controller.
Most LCDs contain Hitachi HD4478 controller.

CG-RAM is the main component in making custom characters.
It stores the custom characters once declared in the code.
CG-RAM size is 64 byte providing the option of creating eight characters at a time.
Each character is eight byte in size.

CG-RAM address starts from 0x40 (Hexadecimal) or 64 in decimal.
We can generate custom characters at these addresses.
Once we generate our characters at these addresses, 
we can print them by just sending commands to the LCD.
Character addresses and printing commands are below.

The first character is generated at address 0x40 to 0x47 and is printed on LCD by just sending a command 0.

The second character is generated at address 0x48 to 0x55 and is printed by sending a command 1.

### How to Generate Custom Characters in CG-RAM

In LCD displays, each character is in a 5×8 matrix.

Where 5 are the number of columns and 8 is the number of rows.
Here is a simple example of how to create letter ‘b’ in CG-RAM.

The Array for generating ‘b’ is char b[7]={0x10,0x10,0x16,0x19,0x11,0x11,0x1E}; That is,

Send address where you want to create character.
Now create your character at this address.
Send the ‘b’ character array values defined above one by one to the data register of LCD.
To print the generated character at 0x40. Send command 0 to command register of LCD.
The table below would explain this more clearly

Reference:\
https://www.electronicsforu.com/technology-trends/learn-electronics/16x2-lcd-pinout-diagram
