JOTEGO

Popeye Public Release

Get ready for a real classic arcade: simple gameplay yet very addictive! Ideal to play with the kids during Christmas. I am happy to announce the public release of Popeye.

Although the core is better than the beta version, particularly in sound, it is still not complete. That's why the OSD colour is yellow. It will become green, and finally grey as the core matures. I am releasing the source code so other developers may take part in it too. Here's the list of pending tasks:

* VGA ...

F1 Dream Public Release MiST and MiSTer

Santa's little present for Christmas eve is a gamepad driving game: F-1 Dream!

Controls:
   button    A: slow
   button    B: fast
   buttons A+B: turbo
   no buttons : break

This game runs on the same PCB as Tiger Road but the devices soldered are different. This game has an MCU added and no second Z80 as it has no ADPCM voices. Nonetheless, it does have the ADPCM decoder sol...

Double Dragon Beta for MiST(er)

(español abajo)

After three weeks of intense work, here it is for your enjoyment: Double Dragon!

The core follows the original schematics, which I eventually found, and there are

no compromises regarding accuracy. The only point I need to check is whether the 6801 CPU core used is really cycle accurate or not. I will use Andrew's board for that.

This is a nice piece of hardware: giant sprites and great FX sound. These came with a price: memory size. The game ...

How Layer Priority Works (and GnG update)

A nice graphical effect is to have the characters go underneath elements in the screen. Like the soldier behind the palm tress in Commando.

One way to create this effect is to have that background drawn directly on the sprite layer, using sprites as though they were tiles. That is the approach followed in Commando. If you boot up Commando in your FPGA and press F10 the sprite layer will disappear. You'll see that along with the soldiers, the top of the palm trees and th...

Announcement: Tiger Road Raffle Winner

I sent emails a couple of days ago with each person's number for the raffle. I asked Torlus to give me a random number today to pick up the winner. Why Torlus? Torlus is one of the pioneers in FPGA retro cores. He developed the initial versions of many beloved cores such as the Megadrive or the Jaguar ones.

After checking the list, I found that the winner is actually a somewhat public person. Retro RGB! Congratulations! Retro RGB was one of the first people to join this...

Cheat Time!

I read this week that on a certain CPS0 game it was possible to select the start level if the test mode DIP switch was set after the game had started. The level was selected by using the price DIP switches. 

So far, I had always set these switches to 1 credit 1 coin. I went back to the core files and added control of the coin slots through the OSD. Then I started Bionic Commando, and could see how for each coin slot setting, the game started at a different level. 2019-12-01 20:41:41 +0000 UTC View Post

Bionic Commando Public Release MiST(er)

I am releasing the Bionic Commando core only slightly improved over the beta. The scroll related glitches are almost gone but there is still no sound. Actually, I am precisely releasing it because there is no sound. In computer simulations of the core I do get sound. The attached file is the output of a long simulation of the MiSTer core.  But for some reason it doesn't work once loaded into the FPGA.

I think at this stage it is better to open it to everyone so other developers ma...

Black Tiger Beta MiST(er)

As you requested on last month's poll, I have worked this month on Black Tiger (beta files here). This is an awesome RPG-ish arcade game from 1987. Manuel Astudillo had sent me this PCB too as he is very fond of this game. Thanks Manuel!

Technically speaking, the game uses the same object (sprite) engine...

Sprite DMA Explained

Español abajo

When Paul Leaman wrote emulators for CAPCOM games he came across a constant writing by the CPU to a misterious address. The CPU didn't seem to be waiting for any data after that writting. It also kept writting the same value. What could that be for? He assumed it was a watchdog. A watchdog is a circuit that counts down and if the count reaches zero, it will reset the whole system. Watchdogs are useful for embedded systems in case the system reaches a non working ...

F1 Dream Beta

Tiger Road PCB has an empty socket for an intel microcontroller (MCU). Also some chip footprints are drawn on the board, but the chips are not there. If you fill those gaps you will just get a F1 Dream PCB! Yes, it looks like these two games shared the same design!

It has been rather easy to make F1 Dream work on the Tiger Road core. It does use an MCU for protection, which I had to add. It turned out the MCU has the same circuit used in Bionic Commando. After a little ...

Tiger Road Public Release

(español abajo)

Today is my son's birthday. To celebrate it with all of you, here is the public release for Tiger Road (also known as Tora e no michi). This includes both western and Japanese versions. The Japanese version has ADPCM voices, but you cannot choose the starting level.

Note that I am going to raffle a bootleg arcade PCB of this game, which I have used during the development ...

Massive Core Update for PSG Sound

As I told you about here, I was working on the cores for better sound. I have the update finally ready. Grab it using the update script, or directly from the binary repository here.

Tiger Road beta has also been updated fixing glitches and sound issues. It is now 100% functional. I just need to finish up the pause...

JT5205: OKI MSM5205 Core Released

Tiger Road uses ADPCM recordings for the Japanese version. I needed a core for the MSM5205 ADPCM decoder and there was not anyone ready to use in the scene. I have written one and made it public here.

This is an important piece of hardware because it is at the core of many arcades. Among them Double Dragon, which I am working towards too as it is a request from many of you :-)

You can hear to...

PSG Sound Update

The old AY-3-8910 3-channel programmable sound generator (PSG), used in the Atari ST and Amstrad CPC computers along many arcades had a second life inside the FM chips YM2203 and YM2610. You may recognize them as the sound synthesizers used in NeoGeo and many arcades from the 80's.

This PSG chip seemed to have an output stage less than ideal. A good amplifier produces an output voltage rather independent from its load. This doesn't seem to be the case for this chip. It seems that the hi...

October Summary

Thank you for your support. This month work has been focused at gaining experience and developing IP. I chose two 16-bit games for this purpose:

- Bionic Commando

• YM2151 for sound. I revised the JT51 core I wrote three years ago. Added clock gating and polished it a bit
• i8751 MCU for protection. I found an open source IP and interfaced it with the core.
• Brightness control (15-bit colour)

- Tiger Road

2019-10-31 15:38:25 +0000 UTC View Post

Tiger Road/Bionic Commando Beta Release

It was my birthday today, so here is a present for you :-)

This has been an intense month with a lot of new components. Trying to gain momentum for the CPS1 task I have worked on two cores that share elements with it:

-The M68000 CPU

-The brightness control (already described here)

-The YM2151 (related 2019-10-27 21:49:23 +0000 UTC View Post

Bionic Commando (CPS1) Brightness Control

Bionic Commando and CPS1 systems feature brightness control. Let's see how that works.

Most arcade games have four bits for each colour component: red, green and blue. These four bits are each a digital signal which can be either 5 Volt or 0 Volt. Arcade boards connect resistors to these signals to produce an analogue scale. Four bits mean that each new bit has twice the weight in the result than the previous one; so the resistors also have a 2x relationship. This is a very cheap way of...

Can you tell the theme?

I have spent a few days bringing my YM2151 core up to some design practices I didn't follow at the time. I have added clock gating, which allows to use a single clock domain for all the FPGA core -this helps synthesis. I have also updated its CPU interface to work better with CPUs that use a different clock enable signal, following the JT12 scheme. I tried not to break the FM synthesis core as that was already proven to be 100% accurate. Yet, I introduced a couple of bugs and had to do some d...

Most Wanted CPS0 Cores

Bionic Commando and Tiger Road cores are fairly advanced now and I will release the beta versions soon. I would like to get a sense of popularity for you guys about remaining CPS0 games. 

Please vote (you can pick more than one) If it is not in the list, write it down. Next month will be CPS0 games too, I'm trying to get them out of the way before moving to a different system. You can see a list of the CPS0 games 2019-10-21 13:30:01 +0000 UTC View Post

1943 Sprites per Line (Core Update)

The 1943 object (sprite) engine was implemented in a custom chip so it wasn't possible to look inside. However, the pin names are similar to those used in other CAPCOM games so it was pretty much obvious how to hook it up to an already working object engine.

Ghosts'n Goblins is designed for a total of 96 objects (sprites) of which up to 24 may fall in the same horizontal line. With a 6MHz pixel clock and 16 pixels per object you can see how 24*16/6MHz = 64 microseconds,...

Tiger Road Raffle

(español abajo)

I am looking now at 16-bit CAPCOM games, particularly Bionic Commando and Tiger Road. I have the Tiger Road PCB and I'd like to give it away among patrons supporting that core.

If you are not already a patron and reading it, join in to support the Tiger Road core and get a chance to win the PCB.

Disclaimer: the PCB is a bootleg version. As these are old games, I will send it without guarantee. But it is working as of today. It is the basis of the FPGA c...