After working with @ironic on the RGB-Pi project for Recalbox now I'm starting a bigger challenge, to create a jamma adapter for RPi fully integrated with amplified sound, buttons, rgb and power all through the gpio without any additional cable.

I have some progress made, for the video we use mode 3 of the DPI output of the Pi, this leaves us free the outputs GPIO9, 10 and 11 where we will connect two MCP23S17 with which we will introduce the buttons, a pin is needed for the CE Or CS (ChipSelect) at the moment use pin 8 that currently belongs to a bit of the RGB blue channel, later we must move this CS to another pin, it is the only pin with the ability to move and this is the only combination of hardware to do everything through the GPIO and I have been studying it for a long time.

This is the prototype:

Here a little video:
https://www.youtube.com/watch?v=FzMKjC5MNCc

To control the MCP23S17 by the SPI port I am using a ControlBlock2 drivers that are open source, but they are compiled in Raspbian, I need the way to integrate them into Recalbox or control the MCP23S17 by different way, at this point I need a Little collaboration from the Recalbox Devs.

Hello, I come to this forum because in other sites I have had many critics saying that I have not discovered anything new or that it was better to use an HDMI > VGA converter.

The first thank you for the interest and the valuation on your part, I have seen that all the questions you have are really interesting and I will try to answer them, sorry for the English I am using translator.

I am using RetroPie only for development since Recalbox is a buildroot and and it's harder to do tests but the idea once finished is to launch a patch or if the developers collaborate a specific version of Recalbox.

The first photo of the prototype is not the complete circuit. I have done this so that it would not be so simple to clone.

If I am thinking of selling it but for those who like to solder I thought of selling only the PCB so that each one builds his own cable at a much lower price and easier to do the circuit from scratch.(If you are patients in a little more than a week I will have the first PCBs)

The idea is that this is mounted inside the SCART housing

I also have the change of resolution for each emulator, there is the section of mame that needs another more complex system but that we can develop it with time, to see if the developers of recalbox help a little, they will get a cable so that it Try them out.

https://www.youtube.com/watch?v=KIVKS6rr4LQ

I have finished assembling the prototype and it works very well, I reduced the noise in the image, for the production version I will change the size of the components to a larger one but basically everything is fine.

I have uploaded a small script that I have done to check all bits of the RGB output separately and also the two audio outputs by the GPIO 18 and 19, this test is also valid for vga666 or other devices that use mode 6 of the DPI.

It is necessary to have raspi-gpio, fbi and alsa.

rgbpi-test.zip

You are complicating life with the HDMI converter, I have already finished 10 cables if you want some. With the cable there is no problem with the hdmi_timings

I have opened a web where I will have updated the latest version of Recalbox for CRT made by me, there are also available cables already assembled ready to use.

rgb-pi.com

As says @Substring still we have a lot of work to make all games to work in their original resolutions but for now there is a lot that can already be enjoyed.

@ian57 Any new? I'm working on the others parts of the circuit but the buttons are the most important.

While I'm waiting for @ian57 to look at the problem on the repo of moving the pins, I'm going to continue with the sound section.

After investigating different options and see which speakers have the most arcade machines that are usually 8 Ohms and between 10 or 15w I think there are two clear options to choose from.

We have the TDA2003 that is a mono amplifier of 10w and option number two is the TDA2005 which is a stereo amplifier of 10w per channel and can be configured in bridging mode getting 20w mono.

The interesting thing about the second option would be in the case of MVS machines that had a stereo wiring in the jamma, could change from 20w mono to stereo 10w + 10w playing with some jumpers and have compatibility with jamma and mvs.

I'm going to prototype two amplifiers and try to configure them with the minimum number of components.

One thing that f**k me a lot is that the encapsulates are not SMD and they should be soldered by hand, they are also upright and they are very ugly, it has occurred to me to knock them down and use the PCB as a heatsink, later also It could be placed on the back of the PCB to save space.

What do you think is more interesting in terms of power? Maybe 20w is too much? The pc2jamma adapter works with a TDA2003.

@substring said in [PROJECT] JAMMA-Pi:

@atg i2cdetect ?

I thing i2cdetect don't detect nothing, I got this message:

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --                

I follow the steps from the readme, my setup on the addresses of the chips in A0 A1 A2 are 000 in one and 100 in the other, I try only with one chip on 000 and the same result, when a run modprobe mk_arcade_joystick_rpi map=1,0x20 the i2c port is enabled on pin 2 or 3 and not on 10, 11 and lose the sincronism of the image.

This can be made because the driver acces to the ports by harware and don't use the DeviceTreeOverlays.

Well I'm back again with the project, following the recomendations of @Substring I change the prototype to allow one MCP23017 conected by the port i2c to talk with Recalbox, I add to the circuit one RGB-Pi PCB for the video output and here is the little frankenstein.

I use the overlay i2c-gpio to move the pins from 2, 3 to 10 , 11

dtparam=i2c_arm=on
dtoverlay=i2c-gpio,i2c_gpio_sda=10,i2c_gpio_scl=11

Now is the moment to enable the option en recalbox.conf, I thing the work is made by mk_arcade_joystick_rpi included but I read in the repo "The branch hotkeybtn now support one more button per player in place of MCP23017 support" and the scheme don't show any pin for i2c, this would be say not longuer avaible use i2c for controllers?

I try to activate on recalbox.conf

 # ------------ D2 - GPIO Controllers ------------ #
## GPIO Controllers
## enable controllers on GPIO with mk_arcarde_joystick_rpi (0,1)
controllers.gpio.enabled=1
## mk_gpio arguments, map=1 for one controller, map=1,2 for 2 (map=1,map=1,2)
controllers.gpio.args=map=1

But the program interfiring with the video output, and I don see what can be user to talk by i2c...

I need a little help from the Devs to talk with Recalbox by i2c and pins 10 & 11, any help is much apreciated!

@llegoff I'm going to discard the SPI prorotype and make another based on i2c because I think with this bus is possible move all the pins.

Thanks for your participation.

@substring Can I offer a bounty to contirbute to the Recalbox project?

This is a preview of the final aspect of the adapter.

The idea is reach a low-cost product for 30€ without any extra cables needed.

@substring Ok, it seems a good way, the only important point is that the integration of the SPI port allows to move the CS pin in any GPIO, this can be done, there are several examples but I do not know how it would have to be done in RB, this point Is the key part of the whole project.

@substring Aaa ok I2C not I2S, I need GPIO3 for h_sync an 5 for one bit of blue.

The DPI is not negociable.
https://www.raspberrypi.org/documentation/hardware/raspberrypi/dpi/README.md

I study all the option for a long time, the only way is use SPI and move CS.

Now before the launch of the 4.1 not is possible compile ControlBlockService2 into the release?

These drivers give support for JAMMA-Pi and ControlBlock at the same time.

@substring I2S use these pinout right?

GPIO 18 (Pin12) is BITCLOCK;
GPIO 19 (Pin 35) is LRCLOCK;
GPIO 20 (Pin 38) is DATA IN;
GPIO 21 (Pin 40) is DATA OUT; (probably not needed for buttons)

These can be compatible with the DPI output for RGB in mode 4 but interfering with the audio PWM output at GPIO19 or 18.
RB can handle MCP23S17 by this port? I see HiFiBerry use these same port, I don't know if is possible use two different functions by the same port, and if is possible you need a DAC and more hardware for the sound and sure you need use the GPIO21 for data out and these collide with the DPI