Hi today. I want to simulate using c on my str9 . for transformer i dont know differnces between saturated trans and simple trans . i use an square wave gen with 20Khz by 555 timer . can i use timer to make the square wave ? pwm ? or dac ? can i use usart ? can i use port ? what will be on the display ? push button ? The only things i want is to isolate between input and output finaly i regulate the output with diff ( void ) . commerical is expensive . thanks alot