PAL Signal Phasor Using ATmega88

The project uses an ATmega88 based demo platform in order to generate PAL video signal by creating a phasor device.

The areas of light intensity that correspond to input voltage level represent the image that can be seen on the screen. The black area can be represented when the signal level is at 0.3V and the white is at 1.0V. the shades will be given by the other voltages. The device can also play music in between video signal horizontal blanking periods with a sampling rate of 15.625kHz aside from generating pseudo phasor shades.

The microcontroller used in this project is clocked at 17.73447MHz which is 4 times the frequency of color carrier wave. This signifies 4 clock cycles per color pixel and a sine wave with controlled amplitude, phase, and constant offset has to be generated in one of those 4 cycles. Since the CPU is limited to a maximum output resolution of one sample per clock cycle, there is no chance of generating a smooth sine wave.

Toggling between two voltages can be done with the aid of one of the timers inside the ATmega88 with two emitter followers in parallel.

Rest of the project