Ideas for a Lower Cost FPGA Board System Based On ECP5

[DocRaptor]

Hello everyone,

I am working on a FPGA Board. It uses an ECP5 with 85k LUTs from Lattice. Most here are familiar with the cyclone ones from Intel. Why than did I choose a FPGA from Lattice and not from Intel? For the ECP5 there is a fully open source toolchain. f4pga.org (formaly SymbiFlow) you can find infos about it. This also support the smaller ice40 from Lattice and Xilinx 7 series is in work. This board should also help people to get in to working with FPGAs.

There is also 64MB SDRAM on it (in two 32MB chips). In the original design I went with only 32MB SDRAM. There is also an interface for more RAM in form of two pinheader for RAM-modules that are also used on the MiSTer, so that an 128MB Module can be added. As Video out it has a VGA-Port, but it runs of three R2R-DACs. Audio is very simple in the moment, just Stereo PWM (and the same circuit like on the MiSTer IO board), but I added a Pinheader, so that a AC97 compatible audio codec can be added. Also two USB 3 ports are on the board for SNAC-modules (not USB). And there is a micro-sd card slot.

At last there is a header for a raspberry pi. The Pi flashes the FPGA. It could also provide the HDMI output and can provide the gamefiles and other stuff. But there could be something different (not a pi): Options: 1. A Lattice Ice40 FPGA (or a ECP5 25K LUTs) and a custom Core. 2. A Raspberry Pico MCU. 3. A ESP32. 4. A ARM9 MPU with integrated RAM from Nuvoton. The Raspberry Pi a the advantage that it can run the toolchain, which means, for developing a core there is no extra pc needed, all can be done on the Pi and the Pi can work together with the fpga. (The Pi has a memory interface on the GPIO header). The other options require more work. For Option 4 these can at least run linux, so there is less work to do (USB Devices like Keyboards and Gamepads and networking over lan).

I already talked about it on an other forum, but it is in german and it is a forum more for the Commodore C64, but it is relative open. (https://www.forum64.de/index.php?thread ... ost1874634) . There are some schematics, but these are old.

What are your opinions and ideas?

It is not meant to replace the MiSTer. It is more for a lower cost entry to FPGA retro gaming and tinkering (the complete package with a pi should cost under 100€). I also want do design boards based on it, which can be put in a mobile console shell like a GBA or DS.

[DocRaptor]

I made a simple overview blockdiagramm of the system, how I intend it to be (simplified). For the Pi and flashing the FPGA, I will just route the pins for the flash, the pins for jtag (and other technical stuff) and around 30 IO (maybe more) for the pi and an (optional) microcontroller to a pinheader, so I can test a bunch of stuff without the need to remake a pcb for every variation.

fixed.png (26.33 KiB) Viewed 3100 times

[Mr. Encyclopedia]

I think RPi + FPGA is probably the future of hardware emulation, and I look forward to seeing how this project develops. The biggest benefit of the De10-nano over other prototyping board is the HDMI port, being able to rely on a Raspberry Pi's hardware instead seems like a slam dunk.

[thisisamigaspeaking]

Very interesting. I prefer this kind of solution so that we aren't bound to a single board maker. The possibility of hybrid emulation is also quite appealing.

I am curious how you can get the cost down to 100€ when a Pi alone is going for that much or more right now? Who would be making the boards?

[DocRaptor]

I think RPi + FPGA is probably the future of hardware emulation, and I look forward to seeing how this project develops. The biggest benefit of the De10-nano over other prototyping board is the HDMI port, being able to rely on a Raspberry Pi's hardware instead seems like a slam dunk.

Thank for your input. (I don't know if slam dunk is posetive or negative. Im not a native english speaker).

With the HDMI: The VGA is generetated with a R2R DAC and I will expose the resulting RGB interface. In combination with some extra pins, which will be on the board, an add-on board for HDMI (with Sound) is possible. This is for people who want the lowest latency on HDMI possible. A ADV7513, what you can also find on the DE10-Nano, can be on it and generate HDMI Video and Audio signal. Problem is: You can't get the ADV7513 nowhere and I did not found a suitable alternative (which is easy to get).

But I think most people will be happy with the HDMI generated by the pi, but I think it is always a good thing to have the option for a lower latency HDMI.

Very interesting. I prefer this kind of solution so that we aren't bound to a single board maker. The possibility of hybrid emulation is also quite appealing.

I am curious how you can get the cost down to 100€ when a Pi alone is going for that much or more right now? Who would be making the boards?

One thing with the pi There is the zero-line of the Raspberry Pi. But thanks to current times these are sold out often.

Other cost cuttings: The ECP5-FPGA I choosing does not have the SERDES for high speed communication like PCIe and similar things. It is just the LFE5U and not LFE5UM or even the LFE5UM-5G. Also I wil the commercial temperature grade one and not the industrial temperature grade one. Originally I wanted to take the fastest speed-grade, but the prices for all went up so it will be the slow one. In the beginning of the the LFE5U-85F-6BG381C cost 27.35€ on mouser, now it cost 50.30€ In higher quantities it only cost 43.84€, but still.

The voltage regulators for 3.3V and 1.1V are M3406 and only cost 5 Cent peer unit and by using two (they are adjustable) and using the same circuit and part (with the exeption of two resistors), it is easier to get more volume and by that getting a lower price.

For the RAM I use two 32MB SDRAM chips, because two of these are still cheaper than a single 64MB chip.

And for the connectors I will design the board to have footprints that can take to different connectors, one cheap one and a brand one. There is a difference of around 8€ in total as I remember right betwen cheap and brand ones and this is a difference. This way there is also a choice betwen price and quality.

With the rest of the components: eletrolyte caps I choose japanese, american and german brand ones and take the cheaper one from what they offer, which is a lot better than crapxon and that stuff. ceramic caps I also choose brand one, but also take the cheaper one from what they offer.
I also try to keep the amount of individual components down, so I can get a lower price based on volume.

What can be a problem is when prices are going up like they do now. So I hope they won't do it like they do it now.

With making the boards: The first batch I will make by myself with a stencil for solderpaste, placing the components by hand and reflow them on a heatplate for smd. Depending on the demand (or: if there is demand), I will choose fitting the situation. Maybe I let JLCPCB, PCBWay or Aisler make the pcbs and populate them. Maybe I buy a pick and place like the lumenpnp, or I let other make and sell them. I don't know jet. I will put everthing open source, so maybe if it become populare, chinese manufacturer wil make them on their own . In this case most people will buy them from them anyway.

[SD2SNES]

Say ECP5 is more powerful than Altera in the old MiSTer? What systems will it support, will it be PS1, N64, Dreamcast? Will you be selling them? Do you have a store website or twitter? Will it have an Emulationstation shell? I like your boards. Please replace Micro-USB with Type-C.

[somhi]

I'm interested in the project and see how it develops.

Is there any git repo with all the design sources of the board ?

[DocRaptor]

I'm interested in the project and see how it develops.

Is there any git repo with all the design sources of the board ?

Currently this projekt is on a "lower" priority. I currently working more on a chip tester/programmer project. But I will use this chip tester/programmer to test some SPI based stuff, so this will help me with this project, because the ECP5 can be programmed via spi. The version of the ECP5 board I wokring on does not have the PI connction and some other stuff will be missing. Instead there will be big header, on which a daugtherboard will be connected, on which the PI will be connected. This will make testing and developing a more final version easy, because a small change does not require a complete redesign.

This here is a copied part from the thread on forum64, where I had talk about it. This will explain some stuff:
"On it I don't put on the PI connector for now. It will be a different connector, on which another board plugs in, where a PI can be pluged in an also carries a mcu.This mcu (or maybe it will be an ice40 fpga) will programm the ecp5 and maybe provide some other stuff.This way I can keep the secondary memory interface of the PI free to talk to the ECP5 and enables hybrid emulation (which maybe enables ps1."

[DocRaptor]

Hello,
after a long time, I have completed the design for the new prototype for the FPGA board.
There have been a few changes compared to the previous version.
Firstly, it now has 64MB SDRAM instead of 32MB SDRAM.
However, I achieved this by using two 32MB chips instead of one 64MB chip, as two 32MB chips are cheaper than one 64MB chip.
Additionally, the Flash and Pi interface have been removed, and I replaced them with a larger connector to test other boards and options.
I'm considering replacing the Pi with another SoC to keep the total cost for a complete system below €100.
Unfortunately, the prices of the Pi's vary significantly (thanks to Corona and Scalpers).
Most of the SoCs in the selection have some form of interface suitable for fast communication with an FPGA, making them useful for other projects as well.
Feel free to use them as inspiration for your projects.
Here is a list of all the candidates (including the Raspberry Pi) with their pros and cons:

Raspberry Pi:
Pros:
-Strong ecosystem
-Lots of software already ported
-Plenty of documentation
-Many people already have it
-Has HDMI (can serve as an RGB to HDMI converter)
-Requires only 5V
Cons:
-Always an additional module
-Compact variants for specific enclosures may be difficult or impossible
-Price fluctuations
-Secondary memory interface requires many pins, leaving fewer pins for other purposes

Nuvoton MA35D1:
Pros:
-Integrated two A35 64-bit ARM cores and an M4 MCU
-Available with up to 512MB RAM in the complete package
Cons:
-Limited documentation (recently released at the end of last year, early this year)
-Unknown prices (refer to point 1 in Cons)
-No HDMI (converter and MUX needed)
-Potential need to adapt all software

Nuvoton NUC980:
Pros:
-Reasonably priced from Digikey and Nuvoton's online shop
-Available with up to 128MB RAM in the package
-Some documentation available
-Requires no complex layout
Cons:
-Only has a 300MHz ARM9 core
-No video output, so a softcore GPU for FPGA is needed
-HDMI converter required
-Potential need to adapt all software

Nuvoton N9H:
Pros:
-Reasonably priced from Digikey and Nuvoton's online shop
-Available with up to 128MB RAM in the package
-Some documentation available
-Requires no complex layout
Cons:
-Only has a 300MHz ARM9 core
-No HDMI (converter and MUX needed)
-Potential need to adapt all software

Microchip SAM9X60D1G:
Pros:
-Available from major distributors
-SiP variant comes with up to 128MB RAM
-Some documentation available
Cons:
-"Only" has a 600MHz ARM9 core
-No HDMI (converter and MUX needed)
-Potential need to adapt all software

Microchip SAMA5D27/28:
Pros:
-Available from major distributors
-SiP variant comes with up to 128MB RAM
-Some documentation available
Cons:
-A5 core clocks at "only" 500MHz
-No HDMI (converter and MUX needed)
-Potential need to adapt all software

Sunplus/Tibbo Plus1/SP7021-IF:
Pros:
-Integrated 512MB RAM
-Four A7 cores
-Additionally, it has an 8051 and ARM9 core
-Has HDMI
-Requires only 3.3V, no other voltages necessary
Cons:
-Limited documentation
-Potentially need to adapt all software
-Availability? (Supposed to be available at Digikey, but I only get a 404 page. Otherwise, only available at the Tibbo Store)

86duino/Vortex86EXm Module:
Pros:
-Strong ecosystem
Abundance of software and documentation due to standard x86 platform
Requires only 5V
Cons:
-Always an additional module
-Compact variants for specific enclosures will be difficult or impossible
-No distributor found for the bare SoC yet
-Expensive
-Graphics must go through an extra chip/module/card or softcore
-Potential need for an HDMI converter
-"Only" 300MHz

Allwinner SoCs:
Pros:
-Affordable
-Now easy to buy from LCSC
-Variants with integrated RAM
-Several designs available
-Some software already ported
Cons:
-Website bugs in English -> no overview possible for half a year
-No apparent interface suitable for fast communication between SoC and FPGA
-Depending on the chip, converter and MUX for video may be necessary.

fpga_module.pdf

(1.48 MiB) Downloaded 149 times

board.zip

(1.81 MiB) Downloaded 112 times