mdj wrote:
It's a shame that the JTAG to PC interface has never beenstandardised.
In the old days the parallel port "Wiggler" type JTAG was a de facto standard. Once the move to USB started everybody came with their own version. The real shame is that the USB interface is really cheap to make but Xilinx put an extra chip in their cable just to hide the protocol! How much money do they get by selling a $15 item for $300 to justify the bad feelings a lot of people have about it? I have to mention that Altera did exactly the same with their cable but the secret didn't last very long. Now you can buy a clone of the Altera's USB JTAG cable for $19 on e-bay!
I'm pleased you've come up with an alternative non-developer way of reprogramming the board. I was going to suggest that a 'core' firmware be developed that allowed access from the actual Apple II host, but your solution is just as good, if not better.
I was thinking about using the Apple for it but the bit file doesn't fit a 5.25" floppy. Requiring a hard disk is worse than the JTAG adapter :)
There is one more exta item that will be very useful with the CB - a 3.3V serial cable. There is one I had already mentioned for $20 but I have read in an embedded system forum about the cheap USB cell phone adapters being just that - 3.3V serial cables. I just had to try one.
http://buffalo.nas-central.org/wiki/Use_a_Nokia_Serial_Cable_on_an_ARM9_LinkstationLook up the item 180369107450 on e-bay. Would you believe $3.58 "buy now" *delivered*? I got a couple at this price. They work just fine. The Ubuntu Linux recognized it as ttyUSB without any driver downloads. Naturally there is a Windows driver too.
What good is it for CB? My soft 50 MHz Z80 uses 2 pins on the JTAG connector (that are not used for JTAG) as a 3.3V serial port. Great for debugging both the soft Z80 and Apple - I can capture all the events on the Apple bus in a buffer and examine them via this port for one thing. Or set hard breakpoints inside Apple's ROM...
I want people to get the developer's tools and hack away. CB is a great toolbox but I can't make end user applications alone.
-Alex.