Converts an RTTL ringtone into verilog using Python - and plays it back using differential PWM modulation
Provide 100kHz clock on "clk" pin, briefly hit reset low ("rst_n") and uio_out[1:0] will play a differential sound wave over a connected piezo speaker (Super Mario)
Piezo speaker connected across io_out[1:0]

| # | Input | Output | Bidirectional | 
|---|---|---|---|
| 0 | ui_in[0] | ui_in[0] | piezo_speaker_p (uio_out[0]) | 
| 1 | ui_in[1] | ui_in[1] | piezo_speaker_n (uio_out[1]) | 
| 2 | ui_in[2] | ui_in[2] | GND | 
| 3 | ui_in[3] | ui_in[3] | GND | 
| 4 | ui_in[4] | ui_in[4] | GND | 
| 5 | ui_in[5] | ui_in[5] | GND | 
| 6 | ui_in[6] | ui_in[6] | GND | 
| 7 | ui_in[7] | ui_in[7] | GND |