This project converts an input clock to a 50x slower output clock that has a set duty cycle.
Project 147 on TT02: 4-bit Multiplier
GitHub repo containing the GDS of the PWM Generator
- Tiny Tapeout 2 Demo Board
no additional hardware needed, however you might consider using an external clock generator capable of 5kHz, as the board can only supply ~2.5kHz.
Select the project by setting the DIP switches to 0b 010 011 010 (pay attention to the endianness!).
The project specifies a 5kHz clock, however others have shown to work as well. This clock is expected on pin in0, and can be suppplied externally. The board also features a built in oscillator with a clock divider. The divisor is chosen by the input byte and locked in by plugging in the provided bridge into the SLOWCLK pins at the top left of the board. After that, the inputs can be used in a regular fashion.
I have tested the project running with the clock divisor initated at 0b 0000 0000 for 2.5kHz it works perfectly fine. Everything will simply run at half the speed, hence the output clock will be at 50Hz.
Now the inputs in2 to in7 can be used to chose a duty cycle between 0% and 50%. As an example, I've set the inputs to 0b 111 000 which equals 0d 14.
To set that value in an start clocking, you need to press the reset button once. If you ever change the value, press it again to update the circuit.
Taking a look at the output PWM signal at out0 with a logic analyzer we can see indeed a frequenzy of 50Hz and a duty cycle of 14%, meaning the circuit operates as expected!.
You can now choose different duty cycles and observe the results in a logic analyzer/oscilloscope or by the changing brightness of the top bar of the 7-segment display.