[hpsdr] [OZY] Initial OZY Schematic Posted For Review andComments - May 10, 2006

[Christopher T. Day]

{Hit the wrong send button the first time.}

NO on the BGA, if possible. I like hand soldering. [although the
drink-warmer + hot air gun technique looks promising. What's so toxic
about solder paste anyway?]

I'm not convinced that we need a lot of FIFO space, but probably can't
convince anyone else. There is nothing bursty about the data going in or
out of the ADC/CODEC; they are clocked, continuous streams. The only
place there could be burstyness is on the USB end with traffic
contention on the USB wire or in the host. However, to drag in my by now
rather smelly dead hobby horse, that doesn't happen with isochronous USB
end points. So, there should be no real need for deep FIFOs. Hence, I
don't think the external RAM is needed. [I have an I2C EEPROM on order
to start playing with Cypress' USB streaming I/O reference design and
see if I can blow some of the flies off that hobby horse.]


	Chris - AE6VK


-----Original Message-----
From: Philip Covington [mailto:p.covington at gmail.com] 
Sent: Thursday, May 11, 2006 7:05 AM
To: Bill Tracey
Cc: HPSDR List
Subject: Re: [hpsdr] [OZY] Initial OZY Schematic Posted For Review
andComments - May 10, 2006

***** High Performance Software Defined Radio Discussion List *****

Hi Bill,

On 5/11/06, Bill Tracey <bill at ewjt.com> wrote:
<snip>
> One thing Phil H has done debugging the Xylo is to have an RS 232 out
that
> he can write to from within the FPGA for debugging.  I'd planned to
add one
> of the FTDI serial -> USB chips to my Xylo to be able to do this via a
USB
> port.  Any interest in doing this on the Ozy's FPGA?

I assume that you are talking about adding RS-232 output from the FPGA
instead of using the RS-232 output of the FX2?  The SN75C1406 that I
am going to use for the FX2's RS-232 has an extra unused RX/TX pair
that I could hook up to a pair of pins on the FPGA for RS-232
capability.  The question is which pins? (which is even more
complicated by adding support for SRAM below).

> Given the uncertainty in how much FIFO space we will need to maintain
> glitch free audio, I'm a bit nervous on how scarce the RAM bits may
> become.  so keeping some capability for an external RAM at this point
seems
> to be a good idea.   If we never populate it great, the 32 pins can be
used
> for other things.

Anyone have suggestions on a 128Kx8 SRAM?  I was looking at using the
ISSI 63LV1024  12 ns which Mouser carries.  Unfortunately the only
package that they stock is the SOJ type so I'd probably put an
optional socket on the OZY for it (if there is room).  Cypress has
some SRAM in the 1Mb size but it looks like it is pretty scarce.

> Regards,
>
> Bill
>

I am already scarce on I/O pins if we add the SRAM with the EP2C5
QFP208 part... I guess I could bump up to the EP2C5 256 BGA part which
would give us more I/O.  Who wants to deal with BGA's ?  No hand
soldering there... maybe hot plate or toaster oven with paste...

73 de Phil N8VB
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