Getting started on SEGA saturn development – Part 2

After the Hello World

After writing a simple hello world, 2 things are needed before proceeding :

  • Get the execution time, (and in turn, frame times) in order to properly write time based animations
  • How to get simple primitives drawn on the screen

Getting execution time

libyaul supplies following function

static uint16_t cpu_frt_count_get(void);

However the return type is a problem : it quickly overflows.
After some digging on discord, as well as examples provided with libyaul:

#include <yaul.h>

#include <stdio.h>
#include <stdlib.h>

uint32_t elapsed_time = 0;
static void _frt_ovi_handler(void);
static uint16_t _frt_overflow_count = 0;

void main(void)
    //initialize dbgio


    uint32_t frame_time = 0 ;
    uint32_t frame_start = 0 ;
    uint32_t frame_end = 0 ;



    /* Reset overflow counter after setting the FRT count to zero in case
     * there's an FRT overflow interrupt */
    _frt_overflow_count = 0;

        elapsed_time += frame_time;
        frame_start = ((65536 * _frt_overflow_count) + (uint32_t) cpu_frt_count_get()) / CPU_FRT_PAL_320_32_COUNT_1MS;
        dbgio_printf("Elapsed time :\t %u
        \nFrame_time :\t %u
        \nFrame Start :\t %u
        \nFrame End :\t %u
        \noverflow cnt :\t %u\n", 
        (unsigned int) elapsed_time,
        (unsigned int) frame_time, 
        (unsigned int) frame_start,
        (unsigned int) frame_end,
        (unsigned int) _frt_overflow_count);

        frame_end = ((65536 * _frt_overflow_count) + (uint32_t) cpu_frt_count_get()) / CPU_FRT_PAL_320_32_COUNT_1MS;
        frame_time = (frame_end - frame_start) ; // get tick count at start 

static void _frt_ovi_handler(void)

Now I’m able to measure the render time and also have the elapsed time.

Getting started on SEGA Saturn development – Part 1

A hello world on libyaul.

Nothing better than a simple hello world to get the feet wet on a new hardware.

My goal, as of April 2021, is to get a simple demo (as in demoscene demo) done by October, for Inercia Demoparty , for the sega saturn.

I’ve already had a USB dev cart for the sega saturn that I’ve brought from cafe-alpha, but had been gathering dust for several years.


As toolchains for the sega saturn I’ve found :

  • Libyaul : available for windows and linux. Tools such as emulators to test the code are already included.
  • Saturn SDK : SDK, libs and documentation.
  • Jo Engine : an open source 2d and 3d engine.

The list is not complete.
I´ve decided to stick to libyaul. On windows it was simple to setup, examples could be easy compiled out of the box, and it has a helpful and active community on discord , where the author of libyaul is also part of.

Hello World


The make file was just a modified makefile already available from the exemples provided with libyaul.


#include <yaul.h>

#include <stdio.h>
#include <stdlib.h>

void main(void)
    //init the subsystem to print debug text to the screen

    //enable vdp2
        dbgio_printf("\x1b[H\x1b[2J");  // clears the screen
        dbgio_printf("Hello World\n");  // actual text
        dbgio_flush();                  // flush 
        vdp_sync();                     // required at the end of each frame

Measure Light – The quest for a light meter for analogue photography – Part One

Light Meter
Light meter with a FTDI USB – Serial Interface for sw development

I love analogue photography, even more when it’s with fully mechanical medium format cameras, such as the Flexaret Automat VII, and the Hasselblad 500c.

However, where are some situations where the correct exposure is difficult to determine. On such cases, one could use a second camera for TTL metering (such as DSLR), a phone app…or a light meter.

On my location, an new sektronick light meter price varies from 109 € to 600 € depending on the model. On ebay you could get an used, cheaper , vintage light meter, but your mileage might vary.

So since the price and availability of light meters were not to my liking, I’ve decided to build my own from scratch, based on an arduino board, with some help of Pedro Virtebo, at Maquinas de Outros Tempos.

Bear in mind this is not the first or last time anyone has done something similar, a simple google search show a ton of similar projects, with different levels of polish. But just implementing these would not give me enough understanding of how a light meter works.

Continue reading “Measure Light – The quest for a light meter for analogue photography – Part One”

SEGA Naomi UNIVERSAL Arcade Cabinet

As someone who likes to collect video games, including arcade hardware, I was looking for a replacent for my current arcade cabinet (a wood cabinet with a 20″ Hantarex 15Khz monitor that I was still reparing).

After scouting the local used market, I came across a Naomi Universal Cabinet, with a sega Naomi board with Virtua Tennis (Power Smash).

The Naomi Universal Cabinet

The Cabinet

The Naomi Universal Cabinet is a Sega Cabinet with a 29″ 31Khz monitor, and JVS wiring released in 1999.
This cab was usually fitted with a sega Naomi Board
And it weights…..117Kgs.

Continue reading “SEGA Naomi UNIVERSAL Arcade Cabinet”

My next step into Analogue Photography : My Darkroom – Part 2

Although the darkroom was functional, there were some issues when using it :

  • The chemicals and trays were not stored near the darkroom desk (and therefore increases the setup time before I can do a single enlargement).
  • Spills would go strait into the wood bench, and the workbench was not waterproof.
  • Safe light position was sub optimal : it did not illuminate the trays properly, since the LED strip was laid on top of the workbench.


My (late 2018) darkroom prior to renovation.
Darkroom after renovation
Darkroom after renovation

Darkroom after renovation , with the safe light on.
Continue reading “My next step into Analogue Photography : My Darkroom – Part 2”

My next step into Analogue Photography : My Darkroom – Part 1


My current (late 2018) darkroom.

3 years ago, on 2015,  I’ve decided to experiment with analogue photography after I got comfortable with digital photography. And I had a simple plan, although without an explicit timeline :

  1. Get into a pin hole photography workshop to see if I really liked the analogue process, before committing more resources into it.
  2. Get started into B&W photography. I chose medium format because I liked the negative size (6×6).
  3. Learn how to develop my own B&W film at home.

Note that in processes that require some investment in tools or equipment such as developer tanks, trays, chemicals, enlargers, etc  I prefer to take a workshop first before buying any equipment, should I decide that my time and resources should be spent elsewhere.

However, after becoming comfortable with developing my own B&W film, it only became obvious what the next step should be : printing.

After taking a workshop on B&W printing, I’ve decided to setup my own darkroom.

My Darkroom

Darkroom, right before use, with the chemicals already on the trays

After deciding to make my own darkroom, several questions had to be answered before investing time and money (and its nothing new for someone who is looking into building one):

  • Location
    • Must be easy to be made light tight
    • Must have room for the enlarger to be permanently assembled
    • Must have room to have 3 trays + assorted materials for enlargements
  • Equipment (Bare minimum)
    • An enlarger
      • capable of handling 6×6 negatives
      • capable of handling contrast filters
    • Safe light
    • 3 Trays
    • Bottles to keep the prepared solutions ready for use.

Thankfully, my garage workshop had the space and was easy to be made light tight without much effort (only 1 small window, a vent and a door), with enough room to spare.


Materials / Tools

Supplies used. Unfortunately I was unable to obtain them locally.

Some of the equipment, such as the trays and RC paper, I’ve already had from my pinhole experiments.

However, the enlarger had to be sourced from a store 50 Kms away – I was unable to source it locally.
The multigrade filters was also purchased from the same store.

I was able to source an Meopta Opemus 6 enlarger, with an 80mm lens.
The Enlarger was in a very good state (it was brought a trusty store). With a bit of maintenance, it got even better.

Opemus 6 (minus the head) under maintenance : the condenser was disassembled for cleaning. Metal rails were cleaned and lubricated.

As for the safe light, I sourced a RGB Led strip locally. So far, when set to red, no fogging was observed on the enlargements.

RGB led strip being used as a safe light.  

I’m still lacking some equipment, that although it is not crucial, it will make my life easier :

  • An easel.
  • A focus finder.
  • An timer for the enlarger (probably going to build my own).

For the time being, for the first darkroom, although usable, there is still some more work such as :

  • Better separation between the dark and wet areas.
  • The enlarger should be enclosed, probable with a curtain
  • Forced ventilation must be implemented. 

To be continued…..

The quest for a Home Monitoring System : Part 3

The quest for a Home Monitoring System : Part 3

Sensor Modules for data acquisition

Hardware choices

The initial sensor module was done with an Arduino + DS18B20 sensor and a ENC28J60 ethernet chip. It was pretty fast to build a prototype that would send data via ethernet to a server running a LAMP stack.
However, since I want to have sensors trough out the house (including the exterior), it became a problem since I’m unable to pass an Ethernet cable everywhere I might need a sensor module installed.

The cheapest to add wifi capabilities to an arduino based system would be to add an ESP8622 wifi module :

  • They are low priced  – around 1,7€  a piece on ebay.
  • Answer to AT commands via serial communication (thus an arduino board could simply send AT commands to the module with the data).

But upon more reading,  it was also noted that the ESP8266 could be used as a stand alone module, without the arduino hardware. This helps drive the cost and assembly complexity of each module down further. A major plus was the fact that the arduino IDE can be used with the ESP8266, work with most libraries already included, without changes to software development workflow.

Sensor Module Schematics for version 1.0. Notice the few component count.

And since the ESP8266 supports I2C  and 1 wire data buses, any sensor supporting those protocols can be added to a ESP8266 module.

Sensor module variants

ESP8266 based sensor Modules – PCB version 1 and Breadboard prototypes during code development

A total of 3 variants of the ESP8266 based sensor module, as of 17th February, were built:

  • A module only using a temperature sensor (the DS18B20), with no RTC on board. Exists in breadboard form only and it is currently in use.
  • A module using both a DHT22 humidity and temperature sensor, and also a DS18B20 sensor. Also without RTC support. Module was disassembled and parts used on the PCB version 1.0.
  • A module using a DHT22 humidity and temperature sensor, with a DS1337 RTC, as used on my Nixie Clock. This version was built on a PCB designed in KICAD, and it is currently in use.

Continue reading “The quest for a Home Monitoring System : Part 3”

The quest for a Home Monitoring System : Part 2

The quest for a Home Monitoring System : Part 2

Changes to the Home Monitoring System Architecture

Almost a year later, and a working prototype, the development of the monitoring system had reached a standstill, mostly due to the lack of time :

  • On the sensor side , the Arduino + ENC28J60 + DS18B20 combo works, although it is dependent on the availability of a network cable. But the hardware is functional.
  • On the server side , the development of a backend and frontend with the flexibility required (multiple sensor support, dashboard with user selected time intervals, etc)  was starting to take too much time.

Sensor : Arduino + ENC28J60 + DS18B20, Server Side : LAMP stack, chart done with chart.js

So I was faced with a decision regarding the server side of the system:

  • Fully development of a frontend and backend , using a LAMP stack and bootstrap templates. This would take time that I simply don’t have, and the project would probably still be stalled.
  • Or find a solution that would require less effort. And this was only an option when I was introduced to Elasticsearch + kibana stack.

On the hardware side, I had some ESP8622 (ESP-12) modules to try out.

ESP8622 Sensor Module prototype with a DS18B20 temperature sensor

Current Status

Server Side changes

The server side of the Monitoring system was the one that was the most time consuming.

One of the major changes was the replacement of the LAMP stack for elasticsearch and kibana for data storage and  visualization respectively. This removed the need to write a backend and a frontend from scratch. The time that would be spent on writing the back and front ends was spent on the sensor module development (both hardware and software).

Elasticsearch, according to the authors:

” Elasticsearch is an open source distributed, RESTful search and analytics engine capable of solving a growing number of use cases.”

With elasticsearch, the sensor modules sends data in json , instead of sending the data via http get to a php script with the previous Monit System architecture.
And a dashboard with visualizations of the data can be done in minutes.

KIbana Dashboard

Hardware changes

Although the arduino + enc28J60 sensor module was not entirely abandoned, hardware development focus was oriented on the ESP8622 based modules.

The ESP8622 have some interesting advantages over the arduino + ENC28J60 combination :

  • The ESP8622 can be sourced from around  1,7 € a piece (ESP-12) (and it replaces the arduino board and the ENC28J60 in one package)
  • It can be used with the Arduino IDE , and use most of its libraries (no need to learn a new SDK and new tools).
  • No additional network hardware required, since the ESP module is a wifi module first and foremost (DHCP, WPA2 supported out of the box), and thus I could place the sensor module anywhere as long as there is wifi coverage, including the exterior of the house.
  • Less parts per module, since the ESP8622 has an ARM CPU besides the WiFi capabilities : besides the module itself, only the sensor, a RTC (if needed) and some passive components are needed.

However the usage of the bare modules are not as “plug and play” as with arduino boards – additional hardware and wiring required . This is not an issue since the final goal is to have a custom made PCB for the sensor module.


The quest for a Home Monitoring System : Part 1

The quest for a Home Monitoring System : Part 1

General Architecture

For a long , long time I wanted to have a system to monitor, and perform data collection, on my home.
A modular system where I could gather data from indoor and outdoor temperatures to local power consumption.

CasaMonit Initial Architecute proposal
CasaMonit Initial Architecture proposal

The system is meant to be designed in such manner that the server side is fully abstracted from the sensor module side, more sensors modules may be implemented on different hardware platforms. There can be as many sensor modules as required, connected on a single Ethernet network.


Sensor Module Hardware (Prototype)

Prototype Hardware Sensor Module
Prototype Hardware Sensor Module

Continue reading “The quest for a Home Monitoring System : Part 1”