DIY Pi2Jpac Jamma Adapter
- Thread starter virtvic
- Start date
Jon-A-Tron
Active member
Chunksin said:
Always good to have more features but there is lots of other options for doing MAME on HDMI so not something that needs doing if it's a hassle.
Thanks for all the time and support put into the project. JonTron2018-11-22 12:58:29
I'm making slow progress on this at the moment!
Spent several days scratching my head wondering why the Pi would not boot up with Chunksin's updated image only to discover that possibly the file for the Jpac DIY version on his link page is probably the wrong image! I think it's for the Jamma2Pi setup and not the Jpac DIY Pi. However, the link to the updated image at the bottom of page 17 on this thread seems to work for me.
I've now finally got the Pi to boot with the Jamma Pi Thingy menu on my PC monitor but not getting a stable picture on my 15kHz Dino King monitor. It probably just needs a tweek on the chassis to stabilize the picture. I'm assuming that this Pi setup via the Jpac uses negative sync for the monitor? Also, there's jumper pins on the Jpac itself, again assuming that just the 15kHz one needs connecting? Flinnster might be able to confirm?
)
I'm also getting power fluctuations on the Pi itself resulting in the yellow low power lightening bolt on-screen constantly appearing and disappearing. I cranked up the switch mode PSU to 6.2v (which seems far too high!) and whilst it reads a stable 6.2v with a multimeter along the wiring from the PSU, the GPIO pins on the Pi are fluctuating between 5.13 and 5.25 volts (even less on boot up). I disconnected everything connected to the Pi and it's the same power problem. I'm thinking here that either my Pi is faulty or that the pre-moulded mini USB power connecter I'm using is causing the issue. Thankfully, today a parcel arrived in the post with a load of new solder yourself mini USB connectors so I'll make up my own power lead to see if it cures the power fluctuation issue.
Spent several days scratching my head wondering why the Pi would not boot up with Chunksin's updated image only to discover that possibly the file for the Jpac DIY version on his link page is probably the wrong image! I think it's for the Jamma2Pi setup and not the Jpac DIY Pi. However, the link to the updated image at the bottom of page 17 on this thread seems to work for me.
I've now finally got the Pi to boot with the Jamma Pi Thingy menu on my PC monitor but not getting a stable picture on my 15kHz Dino King monitor. It probably just needs a tweek on the chassis to stabilize the picture. I'm assuming that this Pi setup via the Jpac uses negative sync for the monitor? Also, there's jumper pins on the Jpac itself, again assuming that just the 15kHz one needs connecting? Flinnster might be able to confirm?
)I'm also getting power fluctuations on the Pi itself resulting in the yellow low power lightening bolt on-screen constantly appearing and disappearing. I cranked up the switch mode PSU to 6.2v (which seems far too high!) and whilst it reads a stable 6.2v with a multimeter along the wiring from the PSU, the GPIO pins on the Pi are fluctuating between 5.13 and 5.25 volts (even less on boot up). I disconnected everything connected to the Pi and it's the same power problem. I'm thinking here that either my Pi is faulty or that the pre-moulded mini USB power connecter I'm using is causing the issue. Thankfully, today a parcel arrived in the post with a load of new solder yourself mini USB connectors so I'll make up my own power lead to see if it cures the power fluctuation issue.
Woah boy on the voltage. Jesus, are you trying to flambe the pi or wot?
Sounds like you may need to beef up your ground and 5V wires between the jamma edge and the pi itself. For the best way yep, do your own micro-usb connector and don't power the pi from the GPIO (the usb port has a bit of voltage protection that the GPIO doesn't).
Switcher should be on about 5.25-5.30V maximum, giving you 4.98-5.00 at the pi.
Remember that not only does the pi naturally dip in voltage at bootup, but you have some additional stuff drawing power from the pi itself - usually just the jpac and the HDMI->VGA dongle. But if you have a USB sound card, that'll be taking some power too.
On my first build, I disconnected the 5v + gnd lines into the HDMI adaptor cable pcb and manually wired them to the jamma edge to save any strain on the pi itself. However since then I've found the laptop style dongles to be pretty efficient on power.
How is your audio amp wired up?
Finally on the warning icons, they can be disabled.. if you're confident no wiring is bad etc..
There is one for temperature, and another for power. The power one comes on by default if the voltage drops below 4.65V.
Add the following to your config.txt:
avoid_warnings=1 <- removes the warning icons
avoid_warnings=2 <- allows overclock / turbo even during low power or high temp
For the sync it's likely your monitor v-sync I'd say. Although the menus and loading screens run at 800x600 interlaced, so get into a game if you can first, and see how 320x240 is working before messing with monitor too much!
The jumpers on the JPAC are as standard from Ultimarc - I've never changed any of mine.
So that's the top and bottom jumpers labelled 31Khz and 15Khz with the jumper in place and the middle one labelled 25khz left open.
Sync-wise the jpac outputs pretty similar video to Pandoras Box, MVS, PGM and Taito-F3 mobos.
It is however pretty different to older hardware like Sega System 1 / 2 / 16, IREM, Technos pcbs and most bootlegs. So tweak your v-sync pot and see how you go, and only mess with h-sync as a last resort on the default dino monitor (it shouldn't really need any messing).
Sounds like you may need to beef up your ground and 5V wires between the jamma edge and the pi itself. For the best way yep, do your own micro-usb connector and don't power the pi from the GPIO (the usb port has a bit of voltage protection that the GPIO doesn't).
Switcher should be on about 5.25-5.30V maximum, giving you 4.98-5.00 at the pi.
Remember that not only does the pi naturally dip in voltage at bootup, but you have some additional stuff drawing power from the pi itself - usually just the jpac and the HDMI->VGA dongle. But if you have a USB sound card, that'll be taking some power too.
On my first build, I disconnected the 5v + gnd lines into the HDMI adaptor cable pcb and manually wired them to the jamma edge to save any strain on the pi itself. However since then I've found the laptop style dongles to be pretty efficient on power.
How is your audio amp wired up?
Finally on the warning icons, they can be disabled.. if you're confident no wiring is bad etc..
There is one for temperature, and another for power. The power one comes on by default if the voltage drops below 4.65V.
Add the following to your config.txt:
avoid_warnings=1 <- removes the warning icons
avoid_warnings=2 <- allows overclock / turbo even during low power or high temp
For the sync it's likely your monitor v-sync I'd say. Although the menus and loading screens run at 800x600 interlaced, so get into a game if you can first, and see how 320x240 is working before messing with monitor too much!
The jumpers on the JPAC are as standard from Ultimarc - I've never changed any of mine.
So that's the top and bottom jumpers labelled 31Khz and 15Khz with the jumper in place and the middle one labelled 25khz left open.
Sync-wise the jpac outputs pretty similar video to Pandoras Box, MVS, PGM and Taito-F3 mobos.
It is however pretty different to older hardware like Sega System 1 / 2 / 16, IREM, Technos pcbs and most bootlegs. So tweak your v-sync pot and see how you go, and only mess with h-sync as a last resort on the default dino monitor (it shouldn't really need any messing).
Many thanks for your reply Flinnster
I’ve now solved the power issue. It was the pre-moulded mini USB connector causing the issues. Wired up my own solder yourself mini USB connector and now the voltage is nice and stable. Lowered the switcher to 5.17v and a solid 5.12v at the GPIO pins with nothing connected to the Pi.
Not at the stage of wiring up the audio amp yet (I’ve got the same one as you in your photo). Incidentally, I’m not using the JAMMA edge connector for the power, I’ve wired my own 3 pin power connector inside the Dino cab especially for this set up
Now that I’ve got the Pi Jamma Thingy to boot up I’m having trouble getting it to read the game roms! My games menu is blank even after performing an Arcade Rom Scan from the setup menu
I think I’ve tried everything from putting the roms in the “roms” folder on the USB stick, to putting them into the Mame-181 folder, to unzipping the files and also putting them directly onto the rom folder of the micro SD card as well, but still can’t get it to read them! What am I doing wrong?
Once I get a game working on the PC monitor I’ll move onto connecting up the Jpac again and work on tweaking the picture on the CRT monitor, then can look at the sound amp.
I’ve now solved the power issue. It was the pre-moulded mini USB connector causing the issues. Wired up my own solder yourself mini USB connector and now the voltage is nice and stable. Lowered the switcher to 5.17v and a solid 5.12v at the GPIO pins with nothing connected to the Pi.
Not at the stage of wiring up the audio amp yet (I’ve got the same one as you in your photo). Incidentally, I’m not using the JAMMA edge connector for the power, I’ve wired my own 3 pin power connector inside the Dino cab especially for this set up
Now that I’ve got the Pi Jamma Thingy to boot up I’m having trouble getting it to read the game roms! My games menu is blank even after performing an Arcade Rom Scan from the setup menu
Once I get a game working on the PC monitor I’ll move onto connecting up the Jpac again and work on tweaking the picture on the CRT monitor, then can look at the sound amp.
Your USB stick should be FAT32 format and when you first fire up the image with a blank USB stick inserted it should create the correct folder structure automatically.
For AdvanceMame, use the following folder for the rom .zips:
USBSTICK:romsmame-106
For AdvanceMame, use the following folder for the rom .zips:
USBSTICK:romsmame-106
I’ve got some sound issues, some games sound perfect like Bubble Bobble but with Shinobi there’s basically no sound at all apart from some muffled beeps.
This could be my setup. I’m running in mono at the moment using the Pi’s onboard audio jack, routed through China’s finest 12v amp then onto the Jpac. I know some of you fellas have got a USB adapter plugged in the Pi for the audio but I just wondered if it’s just me or do some games with this Pi Jamma Thingy setup have audio issues?
Incidentally, I tried the audio socket on the PiHut VGA Adapter and I get no sound at all.
I know there been previous postings about getting stereo sound/mixing left and right outputs into mono, what’s the general consensus with this?
Picture of my setup below:-
qjuk2018-12-26 22:43:37
This could be my setup. I’m running in mono at the moment using the Pi’s onboard audio jack, routed through China’s finest 12v amp then onto the Jpac. I know some of you fellas have got a USB adapter plugged in the Pi for the audio but I just wondered if it’s just me or do some games with this Pi Jamma Thingy setup have audio issues?
Incidentally, I tried the audio socket on the PiHut VGA Adapter and I get no sound at all.
I know there been previous postings about getting stereo sound/mixing left and right outputs into mono, what’s the general consensus with this?
Picture of my setup below:-
My setup is the same as yours except for an additional cheap USB sound card. The sound from the onboard can be made to work but it's always pretty poor quality compared to the USB card, it's defo worth springing the few extra quid for one imo. For some games you can use a different version of MAME that allows software mixing of the stereo to mono. For example, Tron is a stereo game and if I run it on MAME 172 or 181 I can only get some of the sounds (one of the channels). Using ADVMame I can set it to mono in the settings and voila all sounds are there.
I tried using the resistors method to merge the 2 channels, it worked but I lost too much volume using that chinese amp. Probably would have worked with a beefer amp.
HTH
Dan
I tried using the resistors method to merge the 2 channels, it worked but I lost too much volume using that chinese amp. Probably would have worked with a beefer amp.
HTH
Dan
