Re: [Discuss-gnuradio] re: Low cost hardware option

[Brian Padalino]

On Wed, Jan 12, 2011 at 10:26 PM, Marcus D. Leech <address@hidden> wrote:
> On 01/12/2011 10:01 PM, Brian Padalino wrote:
>>
>> Altera Cyclone IV EP4CGX15 FPGA, Analog Devices AD9861 MxFE, USB2
>> microcontroller (for reprogramming the FPGA) in an ExpressCard/34
>> format.  The FPGA has a hard PCIe 1.1 x1 lane with a hard IP core for
>> PCIe connectivity.  The PCIe interface has an extremely low latency
>> and pretty high throughput - ~200MB/sec full duplex (after overhead
>> and whatnot).  The FPGA would be mostly empty since the PCIe core is
>> hard.  If the F169 package is used, it should be compatible with up to
>> a EP4CGX30 which would give 80 18x18 multipliers and over 1Mbit of
>> embedded memory.  The ExpressCard format can fit into desktop PC's
>> with simple and cheap adapters, or into laptops which have ExpressCard
>> slots.
>>
>> ExpressCard has both an x1 PCIe connection as well as a USB 2.0
>> connection.  I imagine a small USB 2.0 micro used for FPGA
>> configuration and, possibly, a secondary way for samples to enter/exit
>> the FPGA for different use cases (similar to the original USRP).  But
>> the main purpose would be for reconfiguration of the FPGA.
>>
>> Frequency synthesis can be an optional part of the assembly.  I
>> imagine a relatively inexpensive VCTCXO (2ppm accuracy?) along with an
>> Si5338 clock synthesis chip.  The idea, though, is to be completely
>> optional for those who really want it.  Otherwise, the FPGA PLL's can
>> probably be good enough for most people.
>>
>>
>>
> There are a couple of downsides to a PCIe implementation that I can
> think of:
>
>  o not all host platforms are going to have PCIe slots
>  o it's noisy in there!

Agreed on PCIe, though I think less platforms have USB3.

When speaking of noise at baseband (2V driving 50Ohms), assuming you
have a little can over the analog bits, is the noise that high?

Brian