Raspberry Pi cartridge from NES

Hello! This is a retro gaming console based on the Raspberry Pi. In the cartridge from the game console NES. An integrated screen can be used for the game. When outputting the same video via HDMI, it shows the image of the game cover, as well as the core temperature, see the photo. I suggest a little ponastalgic and read about the assembly and configuration of such a device. Carefully, further a lot of traffic and photos.

Nostalgia

In childhood, we, who are now 25-35, loved to play consoles. Then there was no newfangled word of the console, so I will call them that. My acquaintance with consoles began with Dandy (clone NES). Super Mario Bros, Contra, Ducktales, Battletoads are just some of the hits of that time. Then the whole court was going to play with my friend in Sega (Sega Mega Drive), in such hits as Sonic, Ultimate Mortal Combat 3, Contra Hard Corps and more . And when the Play Station came out, I must say, she didn’t get to us right away, the Resident Evil series caused some truly scary delight.


This picture helped me to wipe away a tear of nostalgia. I must say, I'm not the first who came up with the Raspberry Pi inserted into the case of the NES cartridge. Yes, this is not my device. And this cartridge is suitable for these purposes almost perfectly, it is small and beautiful. And inside a lot of space. Judge for yourself.


Inside a Raspberry Pi Zero, a USB hub, and a pair of extension cords. All sticks are planted on hot-melt glue.
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Assembly

I wanted to collect something the same or similar. The same cartridge was selected from NES. Other options are either very small or they don't look very good. As the fiery heart of a retro car made Raspberry Pi 3B. Were purchased on Ali, also, USB connectors with convenient leads for soldering. Here it is.


Oh yeah, you will repeat this project, do not take hit cartridges. There are so few of them left. Take something more common or less known. There is also an option to take a cartridge with Ali, but the original, it warms the soul. My 1986 release.

You will also need a special nes screwdriver screwdriver if the cartridge is screwed into three screws. There are also early versions of cartridges with five screws; they are unscrewed with a conventional flat-head screwdriver. I have just this.

From the cartridge with a stationery knife and a sheet from a hacksaw, all interfering parts are cut and sawed.


With the Raspberry Pi, protruding connectors were soldered. Experts say that you can do without a soldering station, if you first carefully disassemble the connectors with pliers, and then drop out one foot. All glued to the glue. Between connectors USB and raspberry laid insulator of non-melting plastic. Do not forget to connect the GND Raspberry Pi and the USB connector case (not shown in the picture above). Otherwise some joysticks will not work.


The last Retropie was installed on the raspberry . At first, Recalbox was standing , but I refused it, because it does not support the vibration of the joysticks on the Playstation 1 consoles. But I must say, the Recalbox is slightly more convenient in terms of what works out of the box and do not need to tune anything. In Retropie a lot of settings, you can customize infinitely. By this I liked him.
That's what happened. Connect any joysticks with xinput.

Screen

Appetite comes with eating. How about embed screen in a cartridge? To play or display the image of the game cover. Such a screen has been ordered. This is an 800 * 480 3.5 inch screen with a parallel DPI interface that uses almost all GPIO Raspberry Pi. It works for me in 120 Hz mode (but the render is still 60 Hz), the response is instant. The only negative is the 6-bit matrix. Only 262,144 colors. Although, in general, it is not particularly noticeable, judge for yourself.

Screenshot from the game Comix Zone (Clickable)

All the legs from the screen and the Raspberry Pi were soldered. The screen was soldered with two cables from an old IDE cable. Under the screen installed mortgages in 5mm, it does not touch the bottom wall of the cartridge. Electrical tape is glued around the perimeter of the display so that there are no side lights. All glued to the glue. On the top cover, I cut through the window and pasted glass 2mm thick.


In order to run the image output on this screen, you need to fix the config / boot / config.txt . I recommend WinSCP program for Windows owners, which, when connecting to Raspberry Pi via SSH, gives the presentation of files as in Total commander'e. Very comfortably. Especially if you run it in shell mode sudo su - , which gives access to all files.

Unfortunately, when the DPI screen is on, video output via HDMI does not work. Therefore, I created two config files in the / boot / folder, one config_hdmi.txt , the second config_dpi.txt . In the config_hdmi.txt config, the resolution is 1080p60Hz and overscan is removed. config_dpi.txt contains the DPI screen settings.


Switching configs will be our autoscript which is available on the network.
\\ 192.168.x.xxx \ configs \ all \ autostart.sh or in the folder on the device /opt/retropie/configs/all/autostart.sh


A script was also written switchscreen.sh , which should be put in / home / pi / RetroPie / retropiemenu / . This script switches configs manually and is available from the main Retropie settings menu. After its launch, it is necessary to pull out the HDMI cable, and after rebooting everything will switch back automatically. Do not forget to register the script

 chmod +x /home/pi/RetroPie/retropiemenu/switchscreen.sh 

In autostart.sh , traces of code are visible, turning off the DPI screen backlight when HDMI is turned on. I copied this script on the Internet, so it doesn’t work on our screen. It would be possible to be confused with transistors to turn off the power of the screen, but why, if we need to display a picture of the cover of the currently running game. You just need to figure out what DPI is.

Parallel Display Interface (DPI)

DPI, as was said, is a parallel interface for screens. Information on this interface one , two, and miscalculated . Well, now it will be here, in Russian.

All attempts to enable DPI by console commands during HDMI operation failed. Maybe doing something wrong. Plan B was adopted for implementation: display the image on a small screen, tugging software by the GPIO legs.

DPI is characterized by the fact that one pixel is transmitted to the display in one clock signal clock. Since we have a 6-bit matrix, these are 18 pins for three colors, and also there are display enable pins (indicates a valid date), h_sync (sets the zero address of the horizontal line in the display controller), v_sync (sets the zero address of the vertical line in the display controller ). Data locking occurs on the falling edge of the clock signal. This is known if you decipher the line “dpi_output_format = 0x6f015” from our config_dpi.txt according to this terminology.




The sequence of bits is shown in the figure above. Each line starting with VSYNC has a full cycle of HSYNC line cycles. This is for one frame. Back and Front porch are the so-called indents of the display, which are in the memory of the controller, but they are not on the screen.

Now we will decode the string “hdmi_timings = 480 0 16 16 24 800 0 4 2 2 0 0 0 120 0 46080000 6” from our config_dpi.txt. There is nothing complicated, just write the parameters in order.


What GPIO legs are used to convey colors is shown in this picture. We have Mode 5. Attention, these are not legs in order, namely GPIO symbols! The remaining signals are Clock - GPIO 0, DE - GPIO 1, VSYNC - GPIO 2, HSYNC - GPIO 3.


A python was quickly installed, the necessary GPIO library and a hello script were written to at least color the screen blue. I also had cognitive dissonance, when Notepad ++ on Windows did not show indents, where they were in nano, while doing line breaks did tabulation, not spaces. By the way, VSCode doesn’t find the same sin, how to fix it.




Too me, Python. It was a surprise for me that the already rendered pixels disappear. Although what I was waiting for, it's obvious.

It was decided to rewrite everything in C. It works faster, approximately several frames per second. The screen ripples like on old CRT monitors or radars. What you need. Retro! I put the code on GitHub .


Access to GPIO is carried out directly through the SoC registers of the BCM2837 chip. Code examples took here .

It all started with a very tiny program, but now the display also shows the processor and memory usage in the form of small scroll bars. The temperature of the processor is drawn like this font.


To run the code, you need to copy the contents of the repository to the / home / pi / lcd_screen / folder (Who knows how to write the path relative to the binary, not the working folder on C under nix? Therefore, only in this folder) and run the following commands.

 gcc ./lcd_screen/lcd.c -o ./lcd_screen/lcd chmod +x ./lcd_screen/lcd 

Or download the binary from releases immediately. To run, you need to type the following. SUDO is required to access GPIO.

 sudo ./lcd_screen/lcd path/file.bmp usec_per_frame 

Where “path / file.bmp” is the path to the image file, it works only with the BMP format, “usec_per_frame” is the delay between frames in microseconds in order not to load the processor in vain.

We automate the launch of our lcd program so that it displays the desired cover when the game is running. Of course, the built-in scraper is used to load covers into Retropie.
Install the image converter. It will convert all formats to bmp, supported by the program. At the same time and resize, so that the images were full screen

 sudo apt-get install imagemagick 

In the / opt / retropie / configs / all / directory, create two files: runcommand-onstart.sh and runcommand-onend.sh . Retropie automatically executes these scripts when loading / exiting any game. Do not forget to write chmod + x to each file.


In the startup script, the presence of a DPI connection is first checked, then an image with jpeg or png formats is searched, rotated to the desired angle, its size is changed and converted to bmp format, then my program is launched with the required parameters.

Cooling

Raspberry Pi 3B is more powerful than Zero, and it needs good cooling. Especially in such a closed case. With a small radiator visible in the photo, after half an hour of playing on any emulator, the core temperature reached 80 degrees and trotting began.


A centrifugal fan of 40 * 30 * 10 mm was ordered, but before it arrived, I just tried to cut a small plate from a 3 mm aluminum plate, measuring 80 * 30 mm. By that time I had dropped all the GPIO pins, so they no longer interfered with the installation of the plate. In addition, I also cut a piece of 20 * 10mm for contact with the chip and made a sandwich from the plates. It exceeded all my expectations, a maximum of 65 degrees on the core.


So it looks inside.

In the end, what

How is it played? Fine! With shouts, smashing gamepads, mutual reproaches. Just like sometime.

No delays and lags were noticed.

The screen, of course, is small, only three and a half inches. Five-inch smartphones spoiled us, but you can play. The text is read, even small. I prefer HDMI.

You can come to a friend, play, portability allows. Related accessories: cables, cables, joysticks, charging take up more space than the console itself.

Sound

Unfortunately, the regular sound of the Raspberry Pi leaves much to be desired. PWM modulation with passive filtering is applied as a sound system. Therefore, a USB DAC for PCM2704 was purchased. Mostly because of its size.

There is a lack of sound output when playing on a small LCD screen, so a 3W microamplifier on the NS8002 was also bought and the speaker from the 8 Ohm tablet was picked up.


All this will fit under the LCD screen. Come, I will set.

Sawing Retropie

The build is over. Below are some less interesting for entertaining reading features of the settings Retropie.

What else can you do

Improve can be infinite. I will give a couple of links that you can do. Write more interesting things to add. Thanks for attention.

• Install dosbox and various ports .
• Put different themes emulationstation.
• Share the screenshots folder.
• Install a web browser.
• Install Retropie Web Manager
• Link Raspberry Pi with the main computer Steam.
• Install Brutal Doom, finally.

He is worth it.