ADC to PC; best/better solution

Hello,

I need help with my project. It´s about A-scan ultrasound, used for eye biometry(more here: http://emedicine.medscape.com/article/1228447-overview). It will serve as a learning tool at my school.

I want to get signal from ADC to PC:
ADC -> buffer -> ATXmega -> USB -> PC
or
ADC -> parallel-to-USB converter -> PC

FPGAs are commonly used in ultrasound devices, but I want to avoid them, because I have no experience with them.

Specifications:
-one data channel
-trandsucer resonence frequency - 2,25 Mhz
-8 bit external ADC atleast 22,5 MSPS
-powering, data and commands via USB
-only data bursts - not continuous data flow:
-ultrasound velocity in water = 1540 m/s = 1.54 mm / us
-eye ball diameter doubled = 50 mm
-one measuring will take 50/1.54 = 32.5 us
-> 22,5 sample on 1 us -> 32.5*22,5*8 = 5850 bits from one measuring
-> 730 bytes per one measurent

I found ADC08B200 from TI, it suits my needs with 8bit, sampling rate, 1kB buffer...

Questions:
Do you know about ADC with bigger buffer memory?
Do you know about any parallel-to-USB converter? Maybe with FTDI chip (didn´t find any that suits my requirements).

I have found few boards like this (**broken link removed**) but it is overkill for my project.

A 200 MS ADC seems to be a bit oversized for digitizing a 2.2 MHz ultrasonic signal.

A Cypress FX2 high speed USB chip seems suitable for the intended application. Many ADC with parallel interface should be directly connectable to the FX2 8- or 16-bit FIFO interface. There's also a FX3 USB superspeed follow-up product, but I believe you won't need it for your throughput range. It uses an ARM instead of a X51 CPU core which may be preferred on the other hand.

You'll need to become familiar with the Cypress toolschain and particularly the programmable interface operation.

Hi,

an ADC --> FIFO --> FT2232H.

The FT2232H includes a 4kBytes FIFO in each direction.
But in async 245 mode the data transfer rate is max 20MBytes per second (50 ns).
It doesn´t need to be big but you will need the external FIFO.

Klaus