[libre-riscv-dev] chinese sponsor, looking to design an ECP5-based dev board

Luke Kenneth Casson Leighton lkcl at lkcl.net
Mon May 6 15:21:41 BST 2019

On Mon, May 6, 2019 at 3:02 PM Samuel Falvo II <sam.falvo at gmail.com> wrote:
> On Mon, May 6, 2019 at 5:44 AM Luke Kenneth Casson Leighton
> <lkcl at lkcl.net> wrote:
> > this would allow us to use one of the FPGAs as a "peripheral" chip and
> > the other(s) as the main CPU.
> This is exactly how I intend on building out the Kestrel-3 today,
> except substituting iCE40HX8K chips for the ECP5K family parts.  One
> chip holds the CPU; a custom interface (which I call ByteLink) that
> bridges to a second iCE40HX8K chip for access to video, audio, etc.
> over a pair of PMOD ports; two UARTs[1]; the flash ROM adapter; the
> static RAM adapter; and a timer to implement mtime/mtimecmp with.  If
> I can fit it, a DMA controller to automate I/O to the mass storage
> UART.  The second chip contains the aforementioned video interface,
> audio interface, access to more RAM, and so forth.

 very cool.

> ________
> 1.  One UART is for the debug terminal, and minicom on the host PC
> will talk directly to it until I can get the 2nd FPGA running with a
> video interface.  The other is intended to provide access to
> PC-/Arduino-hosted mass media (if you remember how Commodore and Atari
> 8-bit disk drives were handled, same idea).  However, I've toyed with
> the idea of replacing this second UART with another ByteLink port
> which would in effect memory-map attached peripherals, greatly
> simplifying both software and the DMA controller.  However, I don't
> know if I'll have enough room.

would 85k LUTs do it?

> > thoughts appreciated, particularly if people believe this may be a
> > saleable product (nothing to do with the Libre RISCV SoC itself)
> If this board existed, and was be licensed under an open hardware or
> copy-left license[2], and the price was affordable to me, I'd buy one
> tomorrow.

well, if you're helping out here, i can likely justify getting one
donated to you.  i don't want to push the chinese sponsor too hard.  i
*think* i've managed to convince them to use the AR9271 for the final
PCB (the one with the SoC), at least.

> I'd want the board to be copyleft licensed, though, so that I could
> have the right to make the changes I'd need for the Kestrel project.
> For example, removing peripherals that aren't used and adding a
> backplane expansion bus, thus basically turning the board into the a
> motherboard for the Kestrel.

 there's this coming out soon enough:


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