Pixel Play Boy

An alternative firmware for STC15F2K60S2-based game kit that turns it into a musical instrument.

Because just soldering few parts together and playing Tetris for few minutes is not fun enough.

Hardware modifications

This firmware requires some changes in original kit schematic:

1. Reconnect resistor from P5.5 (pin 19 of MCU) to P3.5 (pin 26 of MCU). This connects audio amplifier input to hardware output of timer T0, so no (interrupt) code is required to output the signal, MCU hardware does it automatically. This change is necessary for the device to play any sound.

2. Connect P1.5 (pin 14 of MCU) to pin 3 of 5631AS seven-segment indicator. Pin 6 of the indicator is missing. This connection enables displaying dots on the seven-segment indicator, so it's not really critical for device function.

Programming the MCU

The STC15F2K60S2 MCU can be programmed using a USB to TTL serial converter, connected as follows:

MCU pins                     Converter pins
[22] -------/\/\/\/--------- [RxD]
            300R (330R)
[21] ----------|>|---------- [TxD]
            (diode)

Most likely, any converter will work. I used a CH340-based one.

Be sure to select the right MCU type and system clock frequency in the programming application.

How to build

This project uses MCS-51 assembler (as31) created by Paul Stoffregen.

The firmware is assembled by the following command:

as31 -l pixel_play_boy.a31

If you want to have different tone range, tempo options or use a different MCU frequency, you can change constants in generate_freq_tables.py, run it

python3 ./generate_freq_tables.py > ./freq_tables.a31

and replace the tables in pixel_play_boy.a31 by new contents of freq_tables.a31.

Why "Pixel Play Boy"?

One of names present on the kit I've got was "Pixel Game Boy". With this firmware this thing still plays, but not games, so...

Useful links

Another attempt to rewrite firmware of similar device, 1, 2, 3

Full sources of original firmware, direct

Paul Stoffregen's 8051 assembler, sources mirror

Official programming software for Windows