Well,
I've been a bit busy with school, so I'm just now finishing up the hard and softwarre side as far as the USB interface is concerned.
The specs right now are as follows:
* 6KB of internal firmware memory (it offers some diagnostic features such as mem test, ROM view, booting the Mega CD if you have one, etc.)
* 8 MB of SDRAM (100MHz CL2), the upper 1MB or so will be reserved once I get to implement debugging capabilities.
* USB 2.0 (Mini-B) interface (~4.5 MiB/s actual throughput)
* Fits in regular MD cartridge shell
* Quite a few debugging capabilities if you are developing the binary you are debugging (e.g. hardware ports to transfer arbitrary information to the host and whatnot) - of course you will have regular debugging functionality in any case
Here is the BOM as of october 2015:
11.68 Xilinx XC3S50AN Spartan 3AN FPGA
1.36 Alliance Memory, inc. AS4C4M16S-6TCN (4MBit * 16 SDRAM)
0.32 Diodes Incorporated AP2114H-3.3TRG1 3.3V 1A SOT223 regulator
0.32 Diodes Incorporated AP2114H-1.2TRG1 1.2V 1A SOT223 regulator
2.10 3x 74LVC(H)16245A 16-Bit Tri-State Bus Transceivers
3.79 FTDI FT232H 480mbps USB to UART/FIFO interface
0.20 Microchip Technology 93LC56BT-I/OT 2Kbit Config EEPROM for FT232H
1.12 passives (caps/res/etc)
1.53 100MHz Oscillator
= 22.42 EUR
Here are some videos of its current state:
https://www.youtube.com/watch?v=LnFkxlQZF8c
https://www.youtube.com/watch?v=az5gR-P6wYw
(Excuse my voice and the lackluster presentation. It's 9AM and I haven't slept ...)
Cheers!
Eric