I got new code from Jim to address the differences in the new floppy controller. It got past the floppy initialization stage just fine, but got hung up initializing the sound generator board. Turns out that the Xilinx XC9500XL series don’t have the same drive capability of the older, 5V XC9500 series. In theory, the existing pull-up resistors should have helped, but I’ve now had to make an add-on board with additional buffering cicruitry. This will just be for the prototypes, the production units will have them integrated onto the main board.
I’m getting quite a few inquiries about when the project is going to be ready; a number of people have checked in every month to see what’s happening. We’ve finally got the firmware loader written, so at least the main firmware can be updated by the end user. Assuming that the sound generator is the last major hurdle, I think that we are on track for an end of year release.
So, I have started debugging the new CPU board. Amazingly, the first time I powered it up it booted to the sign-on message. It got stuck there, so I hooked up the logic analyzer to see where it was at in the code. As I suspected, it was getting hung up trying to access the new floppy controller. Although the i82078 (the new controller) is register-compatible with the uPD765 (the original DSS-1 controller), it needs to be initialized quite differently. I’m hoping to have a fix for it this week.
Once the floppy is working, the next task will be getting the new USB controller up and running. The firmware that FTDI supplies is supposed to be compatible with the VNC-1 command set, but things are rarely ever that easy 😀
Wow. It’s been eight months since the last update. A lot has happened with the project, as well as my personal life in that time. The project is alive and well, although in suspended animation. I’m actually just about to start testing the new revision of the CPU board. One of the big delays on the project was that FTDI Semiconductor, who make the VNC1L chip that powers the USB part of the CPU board, came out with a new, improved version, the VNC2. Unlike the VNC1, the VNC2 comes with a free IDE (integrated development environment) and royalty-free RTOS (realtime operating system), which allows complete customization of the USB firmware. Previously, you were limited to whatever firmware FTDI developed for the VNC1 (along with its bugs and limitations).
They say things happen in threes, and for me that’s no exception. As of today, I have a new job, a new house, and in January my wife and I will be having our first child. Things like that kind of put weekend projects on the back burner. However, I’m still working on the project. It’s a lot closer than it was, but will still have to wait until the USB firmware matures to a point that it will be user-updatable. The long term plan is to have totally custom firmware tailored for the DSS-1. That is almost as big of a software project as the DSS-1 code. Luckily the out-of-the-box firmware provides enough functionality for 90% of our needs.
I’m putting together a mailing list for all the people who have contacted me wanting to purchase an upgrade kit. So far, it’s well over 100 people, far more than I expected, and a good reason to get the new boards out the door ASAP.