MOS_8502 🇨🇦
@studio8502.ca
(He/Him) Retrocomputing Maker and Designer in Ontario, Canada.
• https://www.patreon.com/Studio8502
• https://ko-fi.com/mos_8502
• https://www.patreon.com/Studio8502
• https://ko-fi.com/mos_8502
There. That's the keyboard diodes arranged. I rather like the look of that.
A conventional design puts those on the bottom, but I don't want to pay for double-sided assembly.
A conventional design puts those on the bottom, but I don't want to pay for double-sided assembly.
November 15, 2025 at 7:53 PM
There. That's the keyboard diodes arranged. I rather like the look of that.
A conventional design puts those on the bottom, but I don't want to pay for double-sided assembly.
A conventional design puts those on the bottom, but I don't want to pay for double-sided assembly.
There. That's the audio mixer sorted.
Big load off my mind, honestly.
Big load off my mind, honestly.
November 15, 2025 at 7:03 PM
There. That's the audio mixer sorted.
Big load off my mind, honestly.
Big load off my mind, honestly.
Sometimes you have to do the boring thing. Today, my boring thing is verifying pinouts in symbols against the datasheets, like this 2MB SRAM chip.
November 10, 2025 at 6:30 PM
Sometimes you have to do the boring thing. Today, my boring thing is verifying pinouts in symbols against the datasheets, like this 2MB SRAM chip.
I said fuck it -- it's only ten dollars extra to boost the system to 2MB of SRAM.
November 10, 2025 at 1:49 AM
I said fuck it -- it's only ten dollars extra to boost the system to 2MB of SRAM.
This is why I don't run off half cocked and produce designs as soon as I think they're done. I forget shit like everyone else. For example, the power switch, which I just now remembered is a thing.
November 10, 2025 at 1:02 AM
This is why I don't run off half cocked and produce designs as soon as I think they're done. I forget shit like everyone else. For example, the power switch, which I just now remembered is a thing.
Here's the memory map for Sentinel 65X. This covers the 16MB address space. It's a bit quirky due to the way the baked-in address decoding works on the W65C265S, but it does work.
November 9, 2025 at 2:57 AM
Here's the memory map for Sentinel 65X. This covers the 16MB address space. It's a bit quirky due to the way the baked-in address decoding works on the W65C265S, but it does work.
Fully routed, DRC passed with no errors or warnings.
Still stuff to do. It will get revised based on feedback from the current spin, which hasn't even shipped yet, and I still have to go over the BOM and make sure it's right. Et cetera, et cetera.
Still stuff to do. It will get revised based on feedback from the current spin, which hasn't even shipped yet, and I still have to go over the BOM and make sure it's right. Et cetera, et cetera.
November 8, 2025 at 4:45 PM
Fully routed, DRC passed with no errors or warnings.
Still stuff to do. It will get revised based on feedback from the current spin, which hasn't even shipped yet, and I still have to go over the BOM and make sure it's right. Et cetera, et cetera.
Still stuff to do. It will get revised based on feedback from the current spin, which hasn't even shipped yet, and I still have to go over the BOM and make sure it's right. Et cetera, et cetera.
Routing the FPGA got a little hairy, but I think I have it managed.
November 8, 2025 at 3:14 PM
Routing the FPGA got a little hairy, but I think I have it managed.
Just some capacitors left to place, and of course the FPGA needs to be routed. Miserable task, but necessary.
November 8, 2025 at 12:51 AM
Just some capacitors left to place, and of course the FPGA needs to be routed. Miserable task, but necessary.
Not a hell of a lot of parts left to place.
November 7, 2025 at 11:55 PM
Not a hell of a lot of parts left to place.
The more I look at it the more convinced I am it's the right direction.
What do you think?
What do you think?
November 6, 2025 at 10:38 PM
The more I look at it the more convinced I am it's the right direction.
What do you think?
What do you think?
Well, routing the keyboard matrix could have gone a lot worse.
November 6, 2025 at 10:29 PM
Well, routing the keyboard matrix could have gone a lot worse.
One day I'm going to find the spoons to get back to making GNUstep look like this. It's entirely within its capability.
Maybe I'm just waiting for Stallman to die, I don't know.
Maybe I'm just waiting for Stallman to die, I don't know.
November 6, 2025 at 4:44 PM
One day I'm going to find the spoons to get back to making GNUstep look like this. It's entirely within its capability.
Maybe I'm just waiting for Stallman to die, I don't know.
Maybe I'm just waiting for Stallman to die, I don't know.
I am not unhappy about that routing.
November 5, 2025 at 8:39 PM
I am not unhappy about that routing.
A larger PCB means room for a beefier, more conventional power supply to generate the +5, +3.3, and +1.2V rails the system needs. Also seen, first traces down on the system bus.
November 5, 2025 at 7:33 PM
A larger PCB means room for a beefier, more conventional power supply to generate the +5, +3.3, and +1.2V rails the system needs. Also seen, first traces down on the system bus.
Very much a work in progress, but still, I think it will look very respectable when it's ready.
65-key keyboard -- basic tenkeyless layout, but with control to the left of "A", super and meta keys left and right of spacebar, and a "break" key in the upper right that generates an NMI when pressed.
65-key keyboard -- basic tenkeyless layout, but with control to the left of "A", super and meta keys left and right of spacebar, and a "break" key in the upper right that generates an NMI when pressed.
November 3, 2025 at 8:43 PM
Very much a work in progress, but still, I think it will look very respectable when it's ready.
65-key keyboard -- basic tenkeyless layout, but with control to the left of "A", super and meta keys left and right of spacebar, and a "break" key in the upper right that generates an NMI when pressed.
65-key keyboard -- basic tenkeyless layout, but with control to the left of "A", super and meta keys left and right of spacebar, and a "break" key in the upper right that generates an NMI when pressed.
Question: If I reduce parts count by having one diode per key row, it will still work, but might, if certain keys are held together, generate ghost presses, though this is unlikely to actually be a real world problem, correct?
November 3, 2025 at 8:01 PM
Question: If I reduce parts count by having one diode per key row, it will still work, but might, if certain keys are held together, generate ghost presses, though this is unlikely to actually be a real world problem, correct?
The real bitch was figuring out which key goes in which spot on the 8x8 matrix, to make routing as painless as possible.
So I punted, and more or less duplicated most of the C64 key matrix. Differences exist, since there isn't a 1:1 correspondence, but it worked out fine.
So I punted, and more or less duplicated most of the C64 key matrix. Differences exist, since there isn't a 1:1 correspondence, but it worked out fine.
November 2, 2025 at 12:12 AM
The real bitch was figuring out which key goes in which spot on the 8x8 matrix, to make routing as painless as possible.
So I punted, and more or less duplicated most of the C64 key matrix. Differences exist, since there isn't a 1:1 correspondence, but it worked out fine.
So I punted, and more or less duplicated most of the C64 key matrix. Differences exist, since there isn't a 1:1 correspondence, but it worked out fine.
I want to allow cartridges to inject audio into the output. Is this a safe, sane way to do that?
November 1, 2025 at 11:54 PM
I want to allow cartridges to inject audio into the output. Is this a safe, sane way to do that?
If I use 16 GPIO and a conventional diode matrix, then the theory of opteration, if I understand it correctly, is that I choose a row by bringing that row output low, leaving the others high, and read back the eight column inputs,with a low value signifying that the key is pressed. Correct or no?
November 1, 2025 at 8:07 PM
If I use 16 GPIO and a conventional diode matrix, then the theory of opteration, if I understand it correctly, is that I choose a row by bringing that row output low, leaving the others high, and read back the eight column inputs,with a low value signifying that the key is pressed. Correct or no?
Behold: An idea I'm playing with for a Sentinel 65X with a built-in keyboard, meant for a wedge style case. The key layout is a conventional tenkeyless, with control to the left of A and Meta left and right of the spacebar.
November 1, 2025 at 2:34 AM
Behold: An idea I'm playing with for a Sentinel 65X with a built-in keyboard, meant for a wedge style case. The key layout is a conventional tenkeyless, with control to the left of A and Meta left and right of the spacebar.
If I redo the I/O like this, ditch the dual clock thing, and move the VERA from its own dedicated IRQ to the main system IRQ, then I free up sixteen total pins, enough to read an 8x8 matrix.
November 1, 2025 at 1:48 AM
If I redo the I/O like this, ditch the dual clock thing, and move the VERA from its own dedicated IRQ to the main system IRQ, then I free up sixteen total pins, enough to read an 8x8 matrix.
Here's how the I/O is currently distributed. I've highlighted the signals I personally could do without. FCLK_EN is used to control which of the two system clock sources is used, and the CDONE and FPGA_RES signals are used to reset the FPGA. Technically it would work without them.
November 1, 2025 at 1:25 AM
Here's how the I/O is currently distributed. I've highlighted the signals I personally could do without. FCLK_EN is used to control which of the two system clock sources is used, and the CDONE and FPGA_RES signals are used to reset the FPGA. Technically it would work without them.
So far, this is my best notion for a custom keyboard for Sentinel 65X.
The theory of operation is thus: Each key is an individual switch, pulled up via a resistor. On press, the key is grounded. Each key goes to an individual input on a CD4021 shift register, one per notional "column".
The theory of operation is thus: Each key is an individual switch, pulled up via a resistor. On press, the key is grounded. Each key goes to an individual input on a CD4021 shift register, one per notional "column".
October 31, 2025 at 6:48 PM
So far, this is my best notion for a custom keyboard for Sentinel 65X.
The theory of operation is thus: Each key is an individual switch, pulled up via a resistor. On press, the key is grounded. Each key goes to an individual input on a CD4021 shift register, one per notional "column".
The theory of operation is thus: Each key is an individual switch, pulled up via a resistor. On press, the key is grounded. Each key goes to an individual input on a CD4021 shift register, one per notional "column".
If you see this, post a vampire that isn’t Dracula
October 30, 2025 at 8:56 PM
If you see this, post a vampire that isn’t Dracula