。Here is a schematic of a previously created kazzo clone. It is basically the same as kazzo_pcb_2 of kazzo0.1.3. The changes are the following three points.
- A circuit has been added to rotate the LED while the cassette is being accessed.
- Improvement of reset circuit
- Change Zener diode of USB bus
１．LED spinning circuit during cassette access
The 3 bits from A8 to A10 in the middle of the address bus of the cassette were converted to 8 LED blinks using 74HC138.
While accessing the cassette, A8 to A10 are accessed over and over again, so O0 to O7 of 74HC138 are turned on many times in order. By connecting the output of the 74HC138 to the LED and arranging the LED in a circle, the LED glow as if they are spinning. Depending on the speed of the PC or USB, the speed of the suction differs, so the rotation of the LED also changes. It is fun to watch.
２．Improvement of reset circuit
A 0.1uF (C5) capacitor has been added to the reset pin of the microcontroller to ensure a reset when the power is turned on.
However, when writing firmware to a microcomputer using the ICSP pin, the writer could not recognize the microcomputer due to this capacitor. If you are writing firmware via ICSP, remove C5.
I attached a reset button, but I only pressed it when re-recognizing kazzo on the PC, basically I did not use it. It was not necessary to have it.
３．Change Zener diode of USB bus
The voltage of the USB bus is 3.3V in specification. Therefore, the Zener diode that limits the voltage of the USB bus was changed from 3.6V to 3.3V.
I don't know why V-USB uses a 3.6V Zener diode, but this time it was 3.3V for safety. I don't think there will be any problems with 3.6V.
The two USB connectors are drawn on the circuit diagram because they can be mounted on either a surface-mounted USB connector or a board that has been converted for DIP.
Here is the improved circuit. Made with KiCad.
The PDF file is here.
If you want this kazzo clone, you can purchase it here ↓
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