All posts tagged mod

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.

Sales have picked up in the new year. Many people are waiting for their tax return I suspect. People seem to be pleased with the modification so far.

The latest firmware version 4.01 adds support for a second USB port. This needs an addtional cable soldered to the VDIP module. I had originally planned to implement this with the combo drives that have the USB port on the front. However the few that I’ve ordered are all flimsy and don’t have mounting holes in the proper position for the DSS-1. One drive looked like the floppy mechanism was salvaged from a surplus parts store, as the top was all scratched and had large chunks of dust (!) inside the floppy. Beware the Sabrent, Nippon Labs, and Bytecc brands.

I’ve also started selling my modded DSS-1’s. I’ve got about 6 left as of this post.

Another improvement I’ve made is to reduce the high frequency whine being induced into the audio path. Routing the two connectors (J10 and J11) over the left side of the KLM-780 board insted of having them come from the back, getting them as far away as possible from the audio jack board, gets rid of the whine when loading and saving. These connectors are the address and data bus connections from the sound generator board which are active any time sound is getting transferred to or from the Wave RAM.

Currently there are 6 kits left and 6 DSS-1’s available.

Well, three sales so far. One kit, one board mod, and one full DSS-1 mod.

Bought another unit off of eBay, unfortunately the seller didn’t pack it very well, and one of the black keys got broken. Good thing I have a parts unit.

V 3.99 has a bunch of fixes in it for USB saving and loading, also adds directory sorting and navigation improvements. Also discovered, while building up more boards, that the byte counter pin on the CPLD needs to be disconnected from the ribbon header, or the signal reflections will corrupt the count.

I’m going to start selling my other DSS-1’s on eBay. Time to start making room for the next project.

Oh yeah, a big thank you to Glen Stegner for his awesome review of the project on his site!

Loose Ends

I’m finally going on vacation! It’s only for a few days but it couldn’t come at a better time.

Jim continues to squash the odd bug here and there in the OS (currently 3.94 as of this entry). Portamento has been added, as has the ability to update the OS from a USB storage device. I’ve started compiling libraries onto flash disks, and am going to include them with the purchase of the kits (while supplies last!).

I’ve documented the install procedure and am in the process of writing the manual. I’ll probably get it done this weekend.

Picked up another used DSS-1. Someone had really bitched it trying to get it open. One side of the case was gouged where someone stuck a screwdriver trying to pry the lid up when the screw stripped. I found the reason why they wanted to open it up, a nice puddle of dried up soda right next to the power supply. Luckily it didn’t get in the electronics.

Also, I have lowered the prices on the LCD and combo drive options, as I’ve found lower priced options for both. The new LCD is yellow-green, not as flashy as the blue-white but still much better than no backlight at all!!

I’m going to start selling off my modded DSS-1’s. I think the software is at a point where it is pretty solid, and updating will be a breeze thanks to the flash ROM.

Finally, after months of debugging, the USB storage part of the kit is functional. Jim has done fantastic work of getting it all up and going. We managed to squeeze all the needed functionality into a 72-macrocell CPLD. The USB transfer speed is very fast, utilizing DMA directly from USB to the wave RAM.

I’m posting the news on the Yahoo! groups DSS-1 user group, but first I’m going to offer the existing kits (at a reduced price) to those of you who have been patiently waiting.

Well, it turns out that the daughterboard had a LOT more problems than I would have liked. On the hardware side, solder bridges and shorts took a lot of time to track down. Also, similar to the main board, the main CPU’s ASTB (address strobe) signal needs to be buffered, as it’s not latching the address bits properly on its own.

Also a couple of dumb errors with the CPLD. I had several versions of the project, and the version I used had the pin placement wrong. Also had the decode logic wrong for the Flash ROM.

The good news is that Jim is working with the new hardware and I think we may see results in a couple of weeks.

Aside from this project, I’ve made some progress on the new revision of the main CPU board. All of the TTL logic is being replaced with two medium-sized CPLD’s and it will have a newer floppy controller and the VNC1L USB controller integrated.

So, I’ve finally gotten the USB daughterboard to boot up. Took a few weekends and some time on the logic analyzer. It doesn’t have the new code needed to run the USB module, but it does have the new expanded memory map and additional RAM. Note to self: next time a design has 10 mil track spacing and power planes, spend the extra money and get a solder mask. I spent most of the debugging time tracking down micrscopic solder bridges.

I sent a test board off to the programmer, Jim, and he sent me a test build of the software. It isn’t quite working yet, so I have to put it back on the logic analyzer. This time, I spent some money and got a proper socket probe for the flash memory, instead of soldering a bunch of test points on the PCB.

Also Jim wondered if it might be possible to upgrade the DAC to 16 bits. In theory it’s possible, since the RAM is now 16 bits wide, but the latches are only 12 bits wide and would have to be replaced. Also the software would have to be changed to allow the synthesis functions to work on full 16 bit words. And unlike the modifications so far, this would actually change (improve?) the sound of the instrument. I’m going to see how the USB mod pans out…then I’ll see if it’s worthwhile doing.