After another year of working on this project where did we get to?
In short not as far as I hoped, though there is slow and steady progress!
For the 2nd run of 10 prototype boards the progress can be summarized as:
- PBI implemented, active only when CPU turbo off.
- Svideo/composite reimplemented using a method closer to GTIA rather than conversion from RGB.
- High resolution (2x and 4x colour clock) modes working, though several alignment and PMG issues remain.
- Experiments at switching to a new CPU (VexRiscV) for running the firmware, I made a good start but still a lot to do before I can switch this!
- OS in block RAM (as ROM) which means turbo is no longer limited to SDRAM access time.
- Steve (917k) made a really cool case and added basic US keyboard support.
Of these I'm most pleased with finally having PBI. Having the faster colour clocks running is also pretty exciting, though would be more interesting with some software.
Much testing was also carried out and bugs captured. I need to find time to work through these.
Panos and I are considering a 3rd run of prototype boards. These will be very close to the run from last year with only these changes:
- Remove video DAC and audio ADC power supplies, these did not work anyway so needed a patch wire.
- Verify footprint of main board IO area vs standard, the power supply was outside the IO area by some mm.
- Adjust paddle voltage level potential divider, if the power supply is <5V (many USB chargers are) the paddles did not work. This allows the level to be adjusted.
- Fix black 'éclaireXL' (cosmetic)
- Widen cutout next to pbi from 3.7 to 4.75mm (or more), some devices could not be connected easily.
- Change REF_N pull up from 4k7 to about 2k. Improves PBI stability.
- Header to connect SIO LED to case.
- Power on switch invert up/down on/off to match 800XL!
- Attempt to reduce cross talk on audio ADC
So nothing major. Additionally a few parts are now obselete so we've updated these. The video DAC CDK3405 has been replaced with an ADV7125 and I'm currently trying to find a compatible for for the 128Mbit EPCS configuration flash.
Is anyone interested in buying a board and helping out? They were ~240USD + shipping last time, though I haven't priced it up yet to see if anything changed!
I'm ideally looking for help with (one of!) these tasks:
- Write an OS patch to support 2x and 4x modes (via E:/S: ideally).
- Debug software and explain why it isn't working. For example Wizard of Wor behaves strangely but it needs someone to dig into the 6502 code to understand what is going on.
- Improve the firmware (OSD, config, USB support, drive emulation etc). This is written in C.
- Help porting the firmware to the new CPU when I get the hardware working.
- Help deciding on new hardware registers.
- Someone who will be interested in the project, chat/discuss aspects of it and generally chivvy me to work on it!
- Someone to write a demo using the high-res modes and turbo!
- Any VHDL help.
- Misc testing
Some videos of the boards in action: https://www.youtube....omputer eclaire
Edited by foft, Thu Jan 25, 2018 2:39 PM.