Message #1 Posted by Eric Smith on 8 Mar 2012, 1:33 a.m.
As of a few minutes ago, the DIY4X is now working with the new microcontroller, which has eight times as much memory, and USB support. That's now 1MB of flash and 128KB of RAM, which gives us a lot more breathing room. The 128KB of flash and 16KB of RAM on the earlier chip was just barely enough for the basic functionality, and not enough for all of the fancy features I want to add.
So far I've done only very minimal testing, verifying that the keyboard and display work, and that it still has basic 41CX-equivalent functionality.
I'm not posting any photos because it doesn't actually look any different at this point, other than the markings on the chip.
I still need to test the other functionality of the chip. Some of it, like the USB port, is wired on the adapter board, but the traces were cut because the USB signal would damage the old chip. Now those traces can be jumpered.
We need to upgrade the two other existing DIY4X prototype units, and do more firmware development and testing, but I think we're not far away from starting work on the DIY5. (Actually Richard Ottosen has done some of the DIY5 hardware design work already.)
It was surprisingly difficult to find a freelance/moonlighting rework technician to replace the QFP100 part. My own soldering skills are nowhere near satisfactory to do that. I finally found a friend who had some assembly work done five years ago, and suggested that I telephone the woman who did the work, though he didn't know whether she was still doing such work, or even still in this area. Luckily for me, she does and is.