Essential SSD1306 Hex Commands 
These commands are typically sent to the display controller to set its operating mode. 

Fundamental Commands
0x81: Set Contrast Control (followed by byte - )
0xA4: Resume to RAM Content Display (Output follows RAM)
0xA5: Entire Display ON (Outputs ignore RAM)
0xA6: Normal Display (0 in RAM = OFF, 1 = ON)
0xA7: Invert Display (0 in RAM = ON, 1 = OFF)
0xAE: Display OFF (Sleep Mode)
0xAF: Display ON (Normal Mode)

Addressing Commands
0x20: Set Memory Addressing Mode (followed by - Horizontal, - Vertical, - Page)
0x21: Set Column Address (followed by Start/End address)
0x22: Set Page Address (followed by Start/End page)

Hardware Configuration
0x40: Set Display Start Line ( - )
0xA8: Set Multiplex Ratio (followed by - )
0xC0/0xC8: Set COM Output Scan Direction (Normal/Remapped)
0xD3: Set Display Offset (followed by - )
0xDA: Set COM Pins Hardware Configuration
Timing & Driving
0xD5: Set Display Clock Divide Ratio/Oscillator Frequency
0xD9: Set Pre-charge Period
0xDB: Set VCOMH Deselect Level
0x8D: Charge Pump Setting (followed by 0x14 to enable) 

Common Initialization Sequence (128x64)

A standard startup routine using these hex values includes: 
Display Off: 0xAE
Clock Div: 0xD5, 0x80
Multiplex: 0xA8, 0x3F
Display Offset: 0xD3, 0x00
Start Line: 0x40
Charge Pump: 0x8D, 0x14
Memory Mode: 0x20, 0x00
Segment Remap: 0xA1 (or 0xA0)
COM Scan Dec: 0xC8 (or 0xC0)
COM Pins: 0xDA, 0x12
Contrast: 0x81, 0xCF
Pre-charge: 0xD9, 0xF1
VCOM Detect: 0xDB, 0x40
Display On: 0xAF 
Note: Detailed timing and electrical specifications can be found in the SSD1306 Datasheet.

I2C Data Transmission
Command Control Byte: 0x00 (Followed by command)
Data Control Byte: 0x40 (Followed by data to be written to GDDRAM) 
