*** New Multiboard RaspberryJAMMA ***

[RGP]

If its 15khz then you'll be getting 31khz out of the HDMI VGA converter and need to then divide the horizontal frequency down by 2 somehow.

I'm not sure how that's accomplished - well, I can think of a way via another small circuit potentially.

That is unless the PI in very low res mode with the software in use has the capability to drive 15khz in those modes.

You won't destroy the monitor as far as I know - it won't like it but it won't kill it so long as you don't leave the 31khz signal going in there for any prolonged period of time. A few seconds definitely won't do anything bad.

Good luck and let us know how you get on.

 

[RGP]

The less fun alternative is to buy an Extron RGB160xi and just plug it in.

At 45.00 that's not a bad way to sort it - might be considered costly but worth experimenting with - might take out some of the pain of finding the right HDMI VGA converter.

Now if only Extron did one that took in HDMI in the first place for a reasonable price and didn't introduce lag into the output.

 

[dee2eR]

Nice work dee2eR - its a great, neat, little solution.

I've
had a read through your posts on aussiearcade and was hoping to get my
existing Pi hooked up to my Astro City. I've grabbed a copy of your SD
card image and wired up my Pi/HDMI-VGA adapter to
the RGB connectors on a little SONY PVM Monitor. I know the PVM works
fine as I've been using it hooked up to a JAMMA board. However, I'm not
having much luck - just garbage on screen.

Looking at your post, I'm guessing I'm hitting one of two issues:

1) The HDMI -> VGA (which ISN'T the active type with a USB port) is the wrong type

2) I have sync issues.

I've ordered what looks to be an identical (from the outside!) HDMI->VGA adapter, I'll try that when it arrives.

You mentioned in your posts "....set the pi to low res and combine the h and v sync."

I've
tried simply combining (soldering the H-SYNC and V-SYNC) cables
together, this didn't work. Do I need something like the "Dodgy Diode"
circuit mentioned here?

http://members.optusnet.com.au/eviltim/scart.htm

Thanks in advance!

You cannot tell from the outside apperance of the HDMI converters whether they can do low res properly or not. All converters look the same and some use the same chips configured differently, and some are just crap.

You could try changing the config.txt settings from this (this makes it work on a scart tv for me, it wouldn't sync otherwise):
# uncomment to force a specific HDMI mode (mode 2 will force 480p, mode 8 240p, mode 6 480i)
## DMT modes
#hdmi_group=1
#hdmi_mode=2
## CVT custom modes
hdmi_cvt=768 240 59.633331 1 0 0 0
hdmi_group=2
hdmi_mode=87

to this:
# uncomment to force a specific HDMI mode (mode 2 will force 480p, mode 8 240p)
## DMT modes
hdmi_group=1
hdmi_mode=8
## CVT custom modes
#hdmi_cvt=768 240 59.633331 1 0 0 0
#hdmi_group=2
#hdmi_mode=87

Else if the problem is the twisted wire sync combination (which could work):

JAMMA is usually negative composite sync.

If this is the problem then you can create the correct circuit by using a 74LS86 (XOR gate).

Pin 1 - H input

Pin 2 - V input

Pin 3 - connect to pin 5 (output of the two signals XOR'd together)

Pin 4 - +5v (add a 1k resistor in series if you think necessary)

Pin 6 - output to monitor sync in composite negative

Pin 7 - GND

pin 14 - +5v

What its doing is taking the H + V and XOR'ing them together, the output will be positive, you can then feed it through another XOR using HI as an input reference along with the signal and it'll come out inverted (negative) at the other side on pin 6.

This is the same as using an LS86 to combine the signals and then an LS04 to invert the final output.

I'm not saying that's the solution but it might be on the right track.

This is how I do it on the board. Easy and cheap.

Hope this helps.

 

[simonden]

The less fun alternative is to buy an Extron RGB160xi and just plug it in.

At 45.00 that's not a bad way to sort it - might be considered costly but worth experimenting with - might take out some of the pain of finding the right HDMI VGA converter.

Now if only Extron did one that took in HDMI in the first place for a reasonable price and didn't introduce lag into the output.

The Extron RGB130xi is the same thing just with a different input connector (9 pin instead of 15 pin) and retrorepair had a couple for sale at £15 each.

 

[corn]

I'll keep tinkering and let you know how I get on.

I also stumbled across this which gives me confidence that it is do-able (https://www.raspberrypi.org/forums/viewtopic.php?f=100&t=86658&start=175 ):

by WalkToFreedom » Wed Oct 14, 2015 12:48 am

Well, it seems that it wasn't quite so complicated after all (unless I have missed something). Pretty sure I've got it outputting 240p to my TV without the need for the GBS-8100. Here's how I did it.




1. I bought an active HDMI to VGA convertor.

2. I made the 'dodgy diode' circuit to join the two syncs as shown here: http://members.optusnet.com.au/eviltim/scart.htm (I think this now is more commonly know as SyncStrike?)

3. I changed/added these settings in config.txt:




disable_overscan=1

framebuffer_width=320

framebuffer_height=240

hdmi_force_hotplug=1

hdmi_group=1

hdmi_mode=8

config_hdmi_boost=4

hdmi_ignore_edid=0xa5000080

hdmi_ignore_edid_audio=1

hdmi_ignore_cec=1

hdmi_pixel_encoding=2

sdtv_aspect=1




I'm hoping that this might work. The config.txt settings differ from those used by dee2eR.

 

[corn]

This is how I do it on the board. Easy and cheap.

Hope this helps.

Our replies crossed. Thanks for the details, I'll get some bits ordered and have a go.

Wonder how many HDMI-VGA adapters I'll need to order before I get a decent one :-(

corn2015-12-22 13:28:48

 

[dee2eR]

Try changing the settings, like I said it got it working for me on a tv based setup.

I used to recommend the converters on ebay with the yellow band around the HDMI cable but have since got 26 that don't work for low res so I don't have a reliable recommendation anymore, I now get mine locaclly so I can exchange them if they don't work out.

EDIT: Thos settings you found elsewhere may work too. I think they used a few options I wasn't aware of. Thanks for posting that.
dee2eR2015-12-22 13:41:14

 

[corn]

Try changing the settings, like I said it got it working for me on a tv based setup.

I used to recommend the converters on ebay with the yellow band around the HDMI cable but have since got 26 that don't work for low res so I don't have a reliable recommendation anymore, I now get mine locaclly so I can exchange them if they don't work out.

Just had a look at the alternative config.txt you recommended. I actually tried that (on the PVM monitor) initially just with one Sync wire connected and it kinda worked but I couldn't stop the picture from rolling. Was no better with 2 sync wires. There just isn't quite enough adjustment on the H-sync pot on the back of the monitor to get it to stabilise :-(

26 HDMI adapters - ouch, thats a real bummer. I was thinking of nipping to Maplins (high street electronics store) for one. I expected to pay a little more but figured I could return it. However, seems they want about £70 for one! What a joke!

 

[corn]

Had another play tonight and managed to get a picture on my PVM monitor. In the end, I just joined the sync wires together and set the config.txt to the standard 240p. I thought I'd tried this before but seems I hadn't.

All rigged up with crocodile clips, no grounds and no shielding etc so not brilliant but it works!

 

[dee2eR]

Fantastic, you had me wondering what PVMs do differently.

Glad you got it working without spending 70 pounds (that's about AU$145, insanity) on a converter.

 

[corn]

I don't know much about your Astro city cab and its monitor (is it VGA or 15khz in those?) but I do run into this sync combine issue a number of times.

I've had intermittent luck just twisting the H+V together, additionally you could be getting positive sync out of the HDMI->VGA and need negative sync at the Astro City monitor.

A number of monitors will give you the "I don't care its a sync signal" approach but some are petty and want it a particular way.

JAMMA is usually negative composite sync.

If this is the problem then you can create the correct circuit by using a 74LS86 (XOR gate).

Pin 1 - H input

Pin 2 - V input

Pin 3 - connect to pin 5 (output of the two signals XOR'd together)

Pin 4 - +5v (add a 1k resistor in series if you think necessary)

Pin 6 - output to monitor sync in composite negative

Pin 7 - GND

pin 14 - +5v

What its doing is taking the H + V and XOR'ing them together, the output will be positive, you can then feed it through another XOR using HI as an input reference along with the signal and it'll come out inverted (negative) at the other side on pin 6.

This is the same as using an LS86 to combine the signals and then an LS04 to invert the final output.

I'm not saying that's the solution but it might be on the right track.

Given that I'd already ordered a 74LS86 I figured I'd solder it up and see how it went.

The picture I'm getting is certainly a lot better than before with the sync's just twisted (but that might just be because I hooked it all up in a heath-robinson style previously). With the 74LS86 the picture is jumping - any ideas what could be the issue?

Video: https://youtu.be/jXQlvb7PjHY

corn2015-12-29 22:45:33

 

[swisstoni]

Just a quick update for this thread, although the board has no video amp which makes some of the games look a bit too dark ive had some success with the brightness side of things changing the gamma setting upto 1.25 or 1.5 in the mame.cfg setting in the Mame4all directory makes the games look as they should now, obviously adjust the gamma to the level required for your screen. Also the brightness can be improved in AdvanceMAME changing the brightness again to 1.25 or 1.5 in the advmame.rc file in the .advance directory in the linux partitition makes the brightness look great but it only works for MAME 106 roms, MAME 078 and FBA (best emulators for CPS2 and CPS3) use retroarch which can be accessed by pressing the player one button and F1 on a USB keyboard theres no brightness option in the menu but im told a shader could be used to increase the brightness so what we really need is the default shader with more brightness, if anyone has one or can point me in the right direction it would be much appreciated I will give it a try and see if it works.

Also this weekend im going to try and upload at least another video showing some vertical games running (with the emulator doing the rotation).

 

[RGP]

Corn, it looks like your monitor is not 100% in range of the output pulse coming from the board.

I get this using 1084's sometimes but on arcade crt's it's fine after I tweak the V hold pot.

That or you have an absence of the V signal altogether or the output voltage is not high enough.

Without a scope trace it might be difficult to say for sure.

 

[gb2000]

So is it possible to get this running via video output to vga but all controls / power handled through jamma ? If so this would be ideal for my current setup

 

[dee2eR]

So is it possible to get this running via video output to vga but all controls / power handled through jamma ? If so this would be ideal for my current setup

Not only possible, actually cheaper by AU$5 if you don't want video on JAMMA at all as it's less parts.

 

[swisstoni]

2 New videos added to the main post, a horizontal video featuring the following games : Aliens, Golden Axe, Nemesis, Robocop, Moonwalker, Pacland, R Type, R Type 2 & The Simpsons and a vertical video featuring, 1942, Commando, DoDonPachi, Flying Shark, Juno First, Pacman, Scramble, Raiden, Slap Fight, Terra Cresta and Varth, apologies the video has been rotated rather than go to the hassle of turning my monitor around its not a great video but you can get an idea of how the vertical games run (ive also do a few close ups of the edges in the videos to show theres no screen tearing), the advancemenu config file has been changed to rotate the menu and MAME4ALL is doing the screen rotation, also I have managed to find a working shader for FBA and MAME 078 so screen brightness can now be changed for all emulators via the software.

swisstoni2016-01-03 21:17:37

 

[devtty0]

Hey, swisstoni - I've got one of these boards, and it does work well, cheers Dee2r! .. however the games are v. dark .. how did you increase the brightness?

also couple more n00b questions:

- how do you select the emulator it boots into - mine always goes to mame4all

- do you know the pinout of the kick harness connector?

thanks!

 

[Fantazia2]

Hey, swisstoni - I've got one of these boards, and it does work well, cheers Dee2r! .. however the games are v. dark .. how did you increase the brightness?

Ultimarc sell a cheap video booster, but it would probably take a bit of work to fit it in.

http://www.ultimarc.com/store/section.php?xSearch=&xSec=11&currency=4

 

[swisstoni]

Ive got an SD card image with the brightness settings let me check with Dee2r if hes happy for me to upload it, F6 should change the emulator when your on the menu, will check on the pinout.

Hey, swisstoni - I've got one of these boards, and it does work well, cheers Dee2r! .. however the games are v. dark .. how did you increase the brightness?

also couple more n00b questions:

- how do you select the emulator it boots into - mine always goes to mame4all

- do you know the pinout of the kick harness connector?

thanks!

 

[dee2eR]

@swisstoni, please upload away. I'm not ready yet to release my new version which includes your changes so be my guest.

@devtty0
The image should be booting straight to the games menu, the games will run in whatever emulator corresponds to the folder you put the roms in.

For mame4all and advmame you can boost brightness on the old image too, from memory in the mame4all config file it's called gamma and in advmames it's brightness. Bump them up from 1.0 to 1.2 or maybe 1.5 for a pretty good improvement to the brightness.

Kick harness pinout is explained in this image:
https://drive.google.com/open?id=0B6UOezdjM-2Ca00tUEdlejV4bEE