Color Generator Theory
The color generator for this system will use a 74-138 de-multiplexer to switch between the different states. A counter will be input into that de-mux to continually switch the states. Below you can see the different states expected to be output on the LCD.
Color Generator State Machine
Each of these colors is output by either setting a single color line or by mixing Red/Green/Blue together to get the desired color, remember the color wheels from kindergarten? Well here's where it can come in handy for making VGA display certain colors.
8 Bit Resistor DAC
This system will be designed so that any of 256 colors across the rainow can be output to the LCD. Given that the state machine is limited to 8 states, I decided to wire only the essential 510Ω resistors up to my design.
The way vga works is 1v = 100% color intesity and all the way down to 0v = 0% color intesity. This resistor DAC allows you to output +5v or GND to the different resistors to get 8 unique voltages because the receiving end of VGA color signals has a 75Ω resistor tied to ground (making a voltage divider!). Only 2 resistors are connected to the blue color pin.
The color generator for this system will use a 74-138 de-multiplexer to switch between the different states. A counter will be input into that de-mux to continually switch the states. Below you can see the different states expected to be output on the LCD.
Each of these colors is output by either setting a single color line or by mixing Red/Green/Blue together to get the desired color, remember the color wheels from kindergarten? Well here's where it can come in handy for making VGA display certain colors.
This system will be designed so that any of 256 colors across the rainow can be output to the LCD. Given that the state machine is limited to 8 states, I decided to wire only the essential 510Ω resistors up to my design.
The way vga works is 1v = 100% color intesity and all the way down to 0v = 0% color intesity. This resistor DAC allows you to output +5v or GND to the different resistors to get 8 unique voltages because the receiving end of VGA color signals has a 75Ω resistor tied to ground (making a voltage divider!). Only 2 resistors are connected to the blue color pin.