Fleafpga ohm minimig

[robinsonb5]

Originally Posted by basman74

Hello Everyone!

I'm the creator of the "FleaFPGA Ohm" board mentioned in this thread.

Just wanted to introduce myself and mention a few recent tweaks added to the Minimig ECS core ported to my board:

Welcome - and nice work!

[Amiga1992]

Welcome basman74! Thanks for making this project a reality.

[kolla]

Great work - I have ordered a couple

Does it only do 68000, or 68020 as well?

Edit: never mind, sysinfo says yes

[Higgy]

Hi Valentin - we have exchanged messages on a number of forums. Glad you got WHDLoad running, it is very good especially in getting old games etc running on higher spec systems.

I was thinking about installing my Flea in a NES cartridge case (i can follow Raspberry Pi Zero instructions!). I can then have MicroUSB extensions etc to avoid strain on the PCB sockets. Looking at a Zero and the Flea Ohm it also seems to use MiniHDMI? So I can use a Mini to Full size HDMI adaptor.
I can also fit some 9 pin dtypes on the cartridge case.

There has been talk of 3.5mm jack output. You have mentioned elsewhere fitting a RC Filter circuit to the relevant GPIO. Sorry my electronics is very basic (I can just follow others design and build!). I saw that the MiST schematic has a audio circuit (same as a RC filter?) straight off the FPGA so I wondered if that would do?

https://github.com/mist-devel/mist-b..._schematic.pdf

(Note that R21should be removed as it blends both audio channels and it was found that it is not correct behaviour).

Well done on the Indigogo and I hope all the extra backers will not cause too much of a headache !
Also nice one on adding the additional Minimig 'hardware' within your port.

[basman74]

Thanks all for your welcome messages, encouraging words and support of my hobby project. I appreciate it!

@robinsonb5: I've been following you over at retroramblings.com for a number of years and like what you've done too

@Akira: I am looking forward to the production run!

@Kolla: Given it is a straight-up port of Minimig ECS, Yes, it is basically a 68020 with some missing opcodes AFAIK.

Cheers, Valentin

[basman74]

Originally Posted by Higgy

Hi Valentin - we have exchanged messages on a number of forums. Glad you got WHDLoad running, it is very good especially in getting old games etc running on higher spec systems.

I was thinking about installing my Flea in a NES cartridge case (i can follow Raspberry Pi Zero instructions!). I can then have MicroUSB extensions etc to avoid strain on the PCB sockets. Looking at a Zero and the Flea Ohm it also seems to use MiniHDMI? So I can use a Mini to Full size HDMI adaptor.
I can also fit some 9 pin dtypes on the cartridge case.

There has been talk of 3.5mm jack output. You have mentioned elsewhere fitting a RC Filter circuit to the relevant GPIO. Sorry my electronics is very basic (I can just follow others design and build!). I saw that the MiST schematic has a audio circuit (same as a RC filter?) straight off the FPGA so I wondered if that would do?

https://github.com/mist-devel/mist-b..._schematic.pdf

(Note that R21should be removed as it blends both audio channels and it was found that it is not correct behaviour).

Well done on the Indigogo and I hope all the extra backers will not cause too much of a headache !
Also nice one on adding the additional Minimig 'hardware' within your port.

To Higgy (and to all!),

I appreciate your positive comments and enthusiasm. I have managed to do a lot with respect to porting the existing Minimig core already, as you've pointed out

You raise a very interesting point about the Video, something that remains an issue for classic Amiga ECS systems everywhere (including the Minimig). I also intend to write about this as an update on the IGG campaign but have been unable to do so due to distractions covered below..

Regarding your suggestion Higgy: I'm afraid it isn't as simple as that. You see, Minimig (as ported to FleaFPGA Ohm) is really only capable of what is intended to resemble 576p (or 576i when Amber is bypassed) screenmode via the video out. It does not upscale nor convert to any other mode (very difficult for me, given my very limited knowledge of the Amiga platform). This limits your display options to TV screens only (I don't know of any dedicated PC monitors that support 576p..). Worse still, minimig core video is clocked at 28MHz, not 27MHz as required for 576p, so some modern digital TVs may 'choke' on the signal while others may not..

Basically, my contribution here (apart from getting an expanded ECS Minimig to work on a Lattice FPGA) is bolting on the ability (itself yet another module merged with the minimig core) to convert the regular scan-doubled video output (ie. 'almost' 576p) into serialized digital form for use on a modern TV..

Now, I am pointing out what are inherent (and presumably well-known) limitations of the existing Minimig core (another is the requirement for PS/2-only devices, something which the MiST currently resolves through an external ARM microcontroller with on-chip USB).

To be honest, my Ohm board does not really offer anything new in the Minimig world (nor do I promise or imply anything to that effect), apart from really tiny form factor and also the fact I have added the electrical provision for more modern interfaces for use by the on-board FPGA.

On a related note: if anyone can point me to an existing free/open solution for an alternate Minimig screenmode (ie. 800x600 or other) I'd be happy to hear of it. In the meantime, best I can do right now is hurry up and get Flea Ohm's user manual (it is an FPGA development board, after all) as well as my latest Minimig HDL files up on github as soon as I can!

Compare also the above scenario with that of the alternate core that was ported to FleaFPGA Ohm - Next186 SoC project: Currently it needs a Monitor or TV that can support both 640x400 and 640x480 modes. Different requirements yet again..

Apologies if I've dampened anyone's enthusiasm from what's been achieved thus far, but I thought it best to be up front and tell the situation as it is - both the good and bad.

Regards,
Valentin
PS: As for your question for the audio out, Higgy: While the circuit you've shown is Ok, I would also recommend adding clamp diodes on the output to help protect the FPGA pins from ESD events as per this PWM circuit example. Either that, you could wait until someone releases a retro 'hat' for my board

[demolition]

Looks quite interesting to being able to get a general purpose FPGA board for that price. Not just to put some existing firmware on it like Minimig and Next186 (which is also nice), but also to use for many other projects and as a learner's board for VHDL. Is the FPGA dev software for this FPGA free for personal use (Lattice Diamond)? Looking at their website, I am not completely sure whether this FPGA is covered with the free version or not?

[basman74]

Originally Posted by demolition

Looks quite interesting to being able to get a general purpose FPGA board for that price. Not just to put some existing firmware on it like Minimig and Next186 (which is also nice), but also to use for many other projects and as a learner's board for VHDL. Is the FPGA dev software for this FPGA free for personal use (Lattice Diamond)? Looking at their website, I am not completely sure whether this FPGA is covered with the free version or not?

Hello. Yes! That is the main purpose of my FleaFPGA Ohm board - as an FPGA experimenters/hackers board that I regard as something of a swiss army knife of digital electronics systems..

You are correct: Lattice Diamond is sw package you need to start developing HDL apps for FleaFPGA Ohm. Diamond is free to download from Lattice's website (requires registration but not a big deal IMHO). There is also a Linux version as well, but I only use the Windows variant because that is how I roll.

Because of the fairly broad scope of potential applications for my board, my limited free time (for what is essentially a hobby project) is being thinly divided between the different working HDL examples (for example: going to a meetup to discuss porting the Propeller 1 Open Source microcontroller to my board in the next few days etc.). So again, the best thing I can do is get the user manual (highest priority) and whatever I've already done thus far up on Github.

Cheers,
Valentin

[kolla]

Originally Posted by basman74

(another is the requirement for PS/2-only devices, something which the MiST currently resolves through an external ARM microcontroller with on-chip USB).

Leaves one wondering if there is any way an attached Pi zero can help with that

[jediknight]

basman74 hi thanks for telling us some more info about your great project , hope all goes well and i cant wait to get my grubby hands on one , and many thanks for making this project its awesome.

[AJCopland]

@basman74 is there much space left in the fpga with the MiniMig core in there? Or is it pretty much full?

[basman74]

Originally Posted by AJCopland

@basman74 is there much space left in the fpga with the MiniMig core in there? Or is it pretty much full?

Thanks for your question! As-ported to my FleaFPGA Ohm, Minimig (with all the enhancements/tweaks added thus far) occupies the following resources on the ECP5 FPGA:

Resource usage:
------------------
LUT4 count: 13776 out of 24288 (56.72%)
Block RAM: 21 out of 56 2KByte-blocks (37.5%)
Slices count: 9465 out of 12144 (77.94%)
PLL count: 2 out of 2 (100%)

Cheers, Valentin

[happymondays]

Hi Valentin, Great project, I will soon back it, congrats for the success.
I wanted to ask whether USB hubs are supported (as the Minimig will need a keyboard, a mouse and at least one joystick and there are two ports for these three). I actually want to use DB9 joysticks with an adapter, I guess that will work fine.

[basman74]

Originally Posted by happymondays

Hi Valentin, Great project, I will soon back it, congrats for the success.
I wanted to ask whether USB hubs are supported (as the Minimig will need a keyboard, a mouse and at least one joystick and there are two ports for these three). I actually want to use DB9 joysticks with an adapter, I guess that will work fine.

Thanks for your kind words and question!

Both the Next186 and Minimig cores shown in my Indiegogo video, are direct ports of existing projects on opencores or github. Both cores (in their current form) will only talk to PS/2 devices (hence why I also made my host ports backwards compatible with PS/2). So, in order to use either of these cores one must use either composite USB (ie. devices that can fall back to PS/2) or be PS/2 only connected via some adapter dongle.

While possible, a USB Hub negotiation adds an extra level of complexity I would prefer not to deal with quite frankly. So this is not an option I'll be looking into at this time (but I won't stop anyone else from doing so if they wish, as the verilog sources will soon be up on Github..).

In my opinion, Joysticks are probably best wired to the GPIO header anyway for FleaFPGA Ohm Minimig.

Regards,
Valentin

[EugeneNine]

I didn't see much in the way of docs, what is needed to 'flash' an image to one?

[basman74]

Originally Posted by EugeneNine

I didn't see much in the way of docs, what is needed to 'flash' an image to one?

Thanks for your question!

I am currently in the process of completing the related user manual for my board (it has been a long drawn-out process, but almost done..).

That said, the process of flashing my Ohm is pretty straightforward. It can be done either via Windows or Linux and requires only three things: 1.) USB cable between PC host and Ohm board 2.) Suitable bit-file image (.vme) for uploading to the Ohm and 3.) Xark's FleaJTAG utility.

For frequent FPGA firmware updates, use of a USB hub is recommended since that cuts the upload time from 5 minutes down to around 35 seconds. Non-permanent uploads to the FPGA's config SRAM area take approximately 15 seconds to complete, with or without a USB hub.

Xark (the creator of FleaJTAG) was kind enough to release the sources for FleaJTAG, including a good how-to around it's usage. You can find those here: https://github.com/XarkLabs/FleaFPGA-JTAG

Regards,
Valentin

[kolla]

I am curious if the serial port of the Minimig ends up somewhere, maybe as TX/RX at VCC level on some GPIO pins? Again, I am thinking of ways to use this together with Rasp. Pi zero, and if TX/RX of fleaboard is matched up with RX/TX of the pi, one can suddenly do networking and lots if other neat things

[basman74]

Originally Posted by kolla

I am curious if the serial port of the Minimig ends up somewhere, maybe as TX/RX at VCC level on some GPIO pins? Again, I am thinking of ways to use this together with Rasp. Pi zero, and if TX/RX of fleaboard is matched up with RX/TX of the pi, one can suddenly do networking and lots if other neat things

EDIT: My original reply is no longer valid: There seems to be a conflict with Retro-Pie joystick pin-out and Raspi UART pins. Because I have decided to initially release FleaFPGA Ohm using retro-pie joystick pin-out as a reference point, that forced me to move the Minimig UART TX/RX pins to 32 and 36 respectively. See: https://github.com/Basman74/Minimig_...tup_README.pdf

Even if a future Minimig firmware release is created specifically for the purpose of direct connection between FleaFPGA Ohm and a Raspberry Pi Zero, I still do not like the idea of connecting the +3.3V rails together between the two. I think this should be left unconnected between FleaFPGA Ohm and Raspberry Pi Zero.

- Valentin

[kolla]

@basman74

Awesome, you can count on me testing it

[Amiga1992]

Get in on it guys, 2 days left, already 150% funded!