Have a look at Tone. You could set it for 40KHz and drive two divide-by-2 flip-flops. Drive one on the rising edge of 40KHz, the other on the falling edge of 40KHz.
Have a look at Tone. You could set it for 40KHz and drive two divide-by-2 flip-flops. Drive one on the rising edge of 40KHz, the other on the falling edge of 40KHz.