Re: [Fx2lib-devel] Allmybrain.com Question/Comment: interested in fx2 cystream

[Nu T. <nu...@gm...>]

Hello Dennis,

Sorry for late reply.  It was night time here in Thailand.

> You'll most likely have to spin a custom PCB to hook an FPGA to the Cypress
> devel board.  I don't know of anyone that sells one.  Perhaps someone else
> on the list has done it.  We also use Xilinx FPGAs and we spun our own board
> with an FX2 and an FPGA.  OpalKelly sells boards with an FX2/FPGA but they
> don't support ISO endpoints and they don't give the source for their
> firmware for you to customize.

Looks like Chris McClelland's board can solve this problem.  :-)

> You can use any Keil/SDCC for any board with an FX2 part.  As long as it is
> an FX2 chip, you can always load your own firmware on the device.  A word of
> caution though, if you don't know the board schematic it can take quite a
> while to get a custom firmware working on a device.  Xilinx FPGAs for
> instance have 4 or 5 different programming modes.  You have to know which
> pins are the mode pins that tell it which mode to program in, and then you
> have to know which pins to send the data to the FPGA on.

Thanks for the heads-up.  I have the schematics for the FPGA board, so
I don't think this will be a problem.

> The Fx2 is great at streaming data from the FPGA to the PC.  We are
> currently doing it at 43 Mbps with the slave fifo interface.  I've done it
> up to about 33 Mbps with a GPIF.

That is a great performance.  Great work on the firmware!

>> If you have more advice/pointer regarding whether I picked the right
>> device to do USB interface, I would really appreciate it.
>
> I'm not an expert in alternatives but I'm sure there are other ways to do
> it.  The FX2 is a pretty common usb controller.  I think many people that
> don't use the FX2 probably use their own custom chip.

FYI, other alternatives I have considered are:

1. OpenCores USB 2.0 function core at http://www.opencores.org/project,usb

Pros: I just need a USB2.0 PHY<-->UTMI chip and feed the UTMI signal
right into FPGA.  Cheap hardware.  Ultra-customizable.
Cons: I suspect this core's Verilog is not yet fully verified.

2. Cypress CY7C68001 EZ-USB-SX2.  This is almost the same as FX2, but
without the 8051 microcontroller

Pros: Avoid learning FX2's 8051 and interface directly to state
machine in FPGA.  The state machine can have ultra high performance.
Cons: well, have to design a potentially very complex state machine in
FPGA.  Any limitation imposed by SX2 is still not solved.

3. Atmel AVR32 family

Pro: Kitchen sink with powerful 32-bit RISC CPU interfacing with its
built-in USB2.0 core.
Cons: may be a total overkill for this project.  Need to learn yet
another platform.

> The dev board provides most of the chips that the fx2 can directly utilize.
>  You don't necessarily need them on a custom PCB.  You can store data in an
> sram for instance, to give more memory to the FX2.  I haven't actually used
> this.  My firmwares to date has all fit in the 16K FX2 ram.

Thanks for this info.  I hope my firmware can fit in 16k on board RAM
as well.  The problem does not look that complex.

Best,
-Nu