Yamaha YPVS controller schematics

This schematic diagram was reverse engineered around 2004 from the original modules my brother asked me to fix. I even posted it on some forums, which unfortunately were killed off by WhatsApp groups.

At the time one of the major challenges was to figure out the internal configuration of the resistor networks which are non-standard types.

The module is composed by an 8051ish microcontroller, an H-bridge, an ADC, a clipping circuit and a hardware watchdog circuit.

CP400 standard ROM cartridge (rev.eng)

Recreation of a standard ROM cartridge for the CP400 Color Computer,  a TRS-Color compatible manufactured by Prologica .  (Github link)

The schematics and the board were reverse engineered from the pictures and article from Rafael Ferrari (thanks!) 

I like to superpose the bottom and top pcb images to figure out the connections using Libre Office Draw. Other programs can be used as long as they provide to adjust the transparency of the images.

I was intrigued by the bodge wires used on the original cartridge but after analyzing the schematics I could see no reason why the jumpers on the board were not used.

The circuit uses a BJT with a speed-up capacitor on its base to form an inverter for the address line A13 that is used to select either chip is active. That was a very common trick in the 1980s to save on glue logic chips. While such components were not present on the board, it was easy to figure this out given the application.   

PIC micro / SDCC on Linux: Quick and dirty installation guide

The standard SDCC and GPUTILS packages does not support PIC microcontrollers, unlike their counterpart on Windows.

To provide them you have to install from the sources. Here's a quick guide on Linux Mint/XFCE 22.3

First Step: Install missing libraries and tools

sudo apt-get update
sudo apt-get install bison flex zlib1g-dev libboost-dev libboost-graph-dev 

Second Step: Download GPUTILS source from https://sourceforge.net/projects/gputils/files/

Create a temporary directory then unpack the sources

cd ~
mkdir tmp1
tar xjf /...path..to...source.../gputils-1.5.2.tar.bz2

 Enter the sources directory, then configure, compile and install 

cd tmp1/gputils-1.5.2/
./configure
make
sudo make install

Third Step: Download  SDCC source from https://sourceforge.net/projects/sdcc/files/
Create a temporary directory then unpack the sources

cd ~
mkdir tmp2
tar xjf /...path..to..source.../sdcc-src-4.5.0.tar.bz2

 Enter the sources directory, then configure, compile and install 

cd tmp2/sdcc-4.5.0/
./configure
make
sudo make install 

It will take forever, but when it finishes, check if the binary was propely installed

cd ~
sdcc -v

 The compiler shall respond with the architectures it support:

SDCC : mcs51/z80/z180/r2k/r2ka/r3ka/sm83/tlcs90/ez80_z80/z80n/r800/ds390/pic16/pic14/TININative/ds400/hc08/s08/stm8/pdk13/pdk14/pdk15/mos6502/mos65c02/f8 TD- 4.5.0 #15242 (Linux)
published under GNU General Public License (GPL)

The final test is to compile a test program with following command line

sdcc -mpic14 -p16f88 --use-non-free teste.c

Test program

#include <pic16f88.h>

// Configurações do Microcontrolador (Fuses)
// Oscilador interno, Watchdog desligado, Master Clear habilitado
unsigned int __at(0x2007) CONFIG1 = _INTRC_IO & _WDT_OFF & _MCLR_ON & _LVP_OFF;

void delay(unsigned int tempo) {
    unsigned int i, j;
    for(i = 0; i < tempo; i++)
        for(j = 0; j < 100; j++); // Atraso simples
}

void main(void) {
    // Configura o oscilador interno para 8 MHz
    OSCCON = 0x70; 

    // Configura RB0 como saída digital
    TRISB = 0xFE; // 1111 1110 (0 = saída)
    PORTB = 0x00; // Inicia todos os pinos em nível baixo

    while(1) {
        RB0 = 1; // Liga o LED no pino 6 (RB0)
        delay(500);
        RB0 = 0; // Desliga o LED
        delay(500);
    }
}

The compilation may generate some warnings but at the end the .hex is generated with success.