I just received the prototype boards from the fab for the first iteration of MINEO. I had to compromise a little to get the project moving (18 bit RAMS will have to wait for a while). The board wound up with:
-XC3S400 FPGA
-XCF02 platform flash
-JTAG port as usual
-2 x 128K (or 512K) SRAMS wired as 16-bit-wide memory
-uSD card connector
-CP2102 USB-serial converter (I am having issues with the circuit, will probably not populate for now)
-USB for power (and serial when it works)
-regulators for 3.3V, 2.5V and 1.2V
-lots and lots of IO
-a small prototyping area near RAMS for extra circuitry
I don't have time to check it now... I am sure I made some stupid mistake and will have to run another PCB.
My hope is to use this board as a reference platform for the 65org16 processor family. My price target is $50; I think I can make it work.
In theory, there is no difference between theory and practice. In practice, there is. ...Jan van de Snepscheut
Looks good. One note: I've had great success using the MCP2200 USB to serial converter. I've gotten speeds up to 1Mb using the Br@y terminal program. Free drivers are on Microchip's website. I used their windows drivers when I was experimenting with the 65Org16 Devboard.
I'll take a look at MCP2200. I've been using factory boards with CP2102 which is why I stuck with it. The 2102 in my CHOCHI-F board did not work - and I copied the circuit to MINEO for expediency. I have to look at it again - I think it's my learning disability acting up again. I am sure it's something simple.
EDIT: MCP2200 seems to need an external oscillator... I'd rather not...
In theory, there is no difference between theory and practice. In practice, there is. ...Jan van de Snepscheut
I believe I used an external clock signal from the FPGA to feed the 12MHz. It is a clean multiple of 60MHz too... Let me know if you do decide to use it, I have the Devboard board layout and can write up a simple schematic.
I am beginning to suspect that a batch of XCF02s and XCF01s I bought on AliExpress are fake. They are slightly different from the XCF01s I have that work (they are flat, the good ones have a dimple on top). I now have 4 CHOCHIs that just don't work.
The MINEO board would not scan via JTAG until I replaced the XCF02 with a good XCF01. I put another XCF02, and it's not scanning again...
I will try sticking and XCF01 again and see if I can actually configure the XC3S400. The '01 is not big enough to keep the bitstream, but is required for the JTAG chain to operate.
EDIT
Argh, the board is too fried now. I'll have to reflow another one.
In theory, there is no difference between theory and practice. In practice, there is. ...Jan van de Snepscheut
I am beginning to suspect that a batch of XCF02s and XCF01s I bought on AliExpress are fake. They are slightly different from the XCF01s I have that work (they are flat, the good ones have a dimple on top)...
How do you know where pin 1 is on the ones you suspect are fake, since these do not have dimples?
Instead of the slight round indentation, they have a silksreened dot! Bastards.
I am getting more and more convinced that the XCF02s are problematic. I built another board. It does not scan with the 'XCF02'. It works without the XCF02 (at least IMPACT recognizes the XC3S400) after I short a couple of pins to complete the JTAG circuit. It also works with my tried and true XCF01s (Both XCF01 and XC3S400 are recognized).
Aw, heck. That's the last thing I need to deal with.
EDIT: At least I have a MINEO board that may work! I'll have to scramble to make a bitstream to flash the LED...
EDIT: I also got the CP2102 working in a semi-populated MINEO board.
In theory, there is no difference between theory and practice. In practice, there is. ...Jan van de Snepscheut
