skeezix
Internal Development
The sharkfin is a TQFP64 avr8 mcu, thats it.
Given that I know the sharkfin seems a bit springy-outy, my first thought was to jump on that as the cause of woes (you know how our brains love to make associations..), but if you think on it for a moment .. that sucker drives the data writes to both banks, just one at a time; it controls the switch too.
So if one bank clears properly -> we know the sharkfin must be more or less okay; the problem must be downstream, at the MUX to the VRAM sort of area.
Possibilities..
- Lose wiring on the A-side of one of the 4 muxes
- Lose wiring going into the VRAM
- Bad solder on the adaptor board for the SRAM to DIP
- Bad RAM (who knows, maybe I cooked or shorted a piece) -> fairly unlikely; these two are well done I think. (My earlier one was a mess, but I took it out once wiring got hectic
Its fairly hard to probe in here, due to the wiring arching all over.
I was fairly tempted to start soldering to perfboards and make it modular .. even had a pile of ribbon cable parts in hand! .. but I think in the end, havin2-3 boards (with say 4-6 or more ribbons between them) seems goofy; pros: build each board separately, and then lay out a mnice header on each side; and then hook them up. Cons: Be annoying to constantly unhook and re-hook every time want to turn over one board to solder or debug it. *HMRF*
Right this moment I'm waffling, more leaning towards screwing together a few perfboards (I've picked up a dozen of the 4x6" one side padded kind for random hacking on.) I maybe could get away with a 2x2 grid of them (a little smaller than my monster breadboard now), but I've also picked up a half dozen little spools of 30AWG wire wrap wire. (Very cheap since its so thin, and tiny little spools.. look smaller than what you'd have on a sewing machine bobbins..); coudl even do something like a 5 board (2 board top row, 3 board middle row?) or something weird like that. Pros .. nice and sturdy, no messing with ribbon cables; Cons: flipping it over all the tiem to work on it, it'd be large; with BB you never flip over, but its tight on surface; with perfboard you work botyh sides, and I'm using smaller wire now.. so more room... but working both sides.
Just not sure
BB is so convenient, its hard to toss it away; but ultimately need to go to a more permanent/semi-permanent build.
At leas tthe 30AWG stuff is tiny; you can bundle like 30 strands of it into the space taken up by a thin pencil.
A few folks really wanty me to go to wire wrap, which would mean buyying a good WW tool, or a WW gun, plus a dozen or two dozen WW sockets; probably another $100 down the drain Not sure if the same spacing or not, maybe need all new perfboard too (ouch). But not really sure it'd help me out, besides taking on yet another ucnertain skill
I'd like ot stay on solder perfboard though.
To hold perfboards together, I'm going to check hardware store see if they have nylon nuts/bolts (assuming they stay tightly done.. maybe should just use regular metal ones..); but a few nylon long nuts/bolts could be nice -- use a drill bit to widen a hole as needed in the perfboard, then put up a long bolt, and tie the nut down to secure it; then coudl use the bolt as a 90degree-turn sort of post .. to organize the wire runs without so much strapping them down. Not sure if that'd work, but cute idea
jeff
Given that I know the sharkfin seems a bit springy-outy, my first thought was to jump on that as the cause of woes (you know how our brains love to make associations..), but if you think on it for a moment .. that sucker drives the data writes to both banks, just one at a time; it controls the switch too.
So if one bank clears properly -> we know the sharkfin must be more or less okay; the problem must be downstream, at the MUX to the VRAM sort of area.
Possibilities..
- Lose wiring on the A-side of one of the 4 muxes
- Lose wiring going into the VRAM
- Bad solder on the adaptor board for the SRAM to DIP
- Bad RAM (who knows, maybe I cooked or shorted a piece) -> fairly unlikely; these two are well done I think. (My earlier one was a mess, but I took it out once wiring got hectic
Its fairly hard to probe in here, due to the wiring arching all over.
I was fairly tempted to start soldering to perfboards and make it modular .. even had a pile of ribbon cable parts in hand! .. but I think in the end, havin2-3 boards (with say 4-6 or more ribbons between them) seems goofy; pros: build each board separately, and then lay out a mnice header on each side; and then hook them up. Cons: Be annoying to constantly unhook and re-hook every time want to turn over one board to solder or debug it. *HMRF*
Right this moment I'm waffling, more leaning towards screwing together a few perfboards (I've picked up a dozen of the 4x6" one side padded kind for random hacking on.) I maybe could get away with a 2x2 grid of them (a little smaller than my monster breadboard now), but I've also picked up a half dozen little spools of 30AWG wire wrap wire. (Very cheap since its so thin, and tiny little spools.. look smaller than what you'd have on a sewing machine bobbins..); coudl even do something like a 5 board (2 board top row, 3 board middle row?) or something weird like that. Pros .. nice and sturdy, no messing with ribbon cables; Cons: flipping it over all the tiem to work on it, it'd be large; with BB you never flip over, but its tight on surface; with perfboard you work botyh sides, and I'm using smaller wire now.. so more room... but working both sides.
Just not sure
BB is so convenient, its hard to toss it away; but ultimately need to go to a more permanent/semi-permanent build.
At leas tthe 30AWG stuff is tiny; you can bundle like 30 strands of it into the space taken up by a thin pencil.
A few folks really wanty me to go to wire wrap, which would mean buyying a good WW tool, or a WW gun, plus a dozen or two dozen WW sockets; probably another $100 down the drain Not sure if the same spacing or not, maybe need all new perfboard too (ouch). But not really sure it'd help me out, besides taking on yet another ucnertain skill
I'd like ot stay on solder perfboard though.
To hold perfboards together, I'm going to check hardware store see if they have nylon nuts/bolts (assuming they stay tightly done.. maybe should just use regular metal ones..); but a few nylon long nuts/bolts could be nice -- use a drill bit to widen a hole as needed in the perfboard, then put up a long bolt, and tie the nut down to secure it; then coudl use the bolt as a 90degree-turn sort of post .. to organize the wire runs without so much strapping them down. Not sure if that'd work, but cute idea
jeff