Search found 47 matches

by alastair
29 Jun 2022, 21:46
Forum: Hardware and software hacking
Topic: Gigatron Clone Ideas
Replies: 46
Views: 1570

Re: Gigatron Clone Ideas

Thanks for taking a look @at67. I was actually thinking how you could "fix" this issue by connecting ~PL to the CEP input of the upper two counters. I took a closer look at the Gigatron schematic and this is exactly what Marcel has done {insert facepalm}. Yes, I totally missed that when I ...
by alastair
29 Jun 2022, 13:56
Forum: Hardware and software hacking
Topic: Gigatron Clone Ideas
Replies: 46
Views: 1570

Re: Gigatron Clone Ideas

fixed.jpg I updated ROMv3 with this fix. I can't create a PR, but this is the diff: --- a/Core/ROMv3.asm.py +++ b/Core/ROMv3.asm.py @@ -2241,11 +2241,11 @@ def trampoline3a(): ld([sysArgs+6]) #22 adda(1) #23 bra(AC) #24 - bra(250) #25 trampoline3b + bra(256-7) #25 trampoline3b def trampoline3b(): &...
by alastair
29 Jun 2022, 03:36
Forum: Hardware and software hacking
Topic: Gigatron Clone Ideas
Replies: 46
Views: 1570

Re: Gigatron Clone Ideas

I was close, but it is the last jump in the image trampoline page. E.g. 0dfd 1406 ld $06,y 0dfe fe00 bra ac 0dff e0bc jmp y,$bc The issue here is the trampoline returns at the end of the page. That causes the program counter to increment the page when it dispatches the trampoline instruction. It hit...
by alastair
29 Jun 2022, 02:16
Forum: Hardware and software hacking
Topic: Gigatron Clone Ideas
Replies: 46
Views: 1570

Re: Gigatron Clone Ideas

I haven't put the oscilloscope on it yet... but here's my theory. SYS_Read3_40 reads 3 bytes by doing two trampolines with code between 0x79-0x7F and one trampoline at the end of the page between 0xFA-0xFF (the pixels are stored in 0x00-0x7F and 0x80-0xF7). Here's the problem: There's a jump at 0x7F...
by alastair
28 Jun 2022, 21:24
Forum: Hardware and software hacking
Topic: Gigatron Clone Ideas
Replies: 46
Views: 1570

Re: Gigatron Clone Ideas

I was suspecting SYS_Draw4, specifically this line . Somehow the Y register gets offset by 2 pages, but on closer inspection it looks like there's something going on with the pixel preceding it. This might be an issue with SYS_Read3_40 reading the third (or is it first?) byte from the wrong location...
by alastair
28 Jun 2022, 16:28
Forum: Hardware and software hacking
Topic: Gigatron Clone Ideas
Replies: 46
Views: 1570

Re: Gigatron Clone Ideas

Thanks for the link! I thought I had seen this somewhere before. I installed the ATtiny85 on the board and I'm using a PS/2 keyboard to get to Pictures. Jupiter crashes the video timing, but the blinken lights still run (weird). All the other built in programs work fine, so it must be some weird tim...
by alastair
28 Jun 2022, 14:50
Forum: Hardware and software hacking
Topic: Gigatron Clone Ideas
Replies: 46
Views: 1570

Re: Gigatron Clone Ideas

I do seem to have one issue though. The pictures are slightly scrambled and the machine crashes after it displays the first image. The new picture app on Rev5A works fine. The following images show Rev3 and Rev4. It will crash as soon as this picture starts scrolling.
pic3.jpg
pic3.jpg (140.36 KiB) Viewed 89 times
pic1.jpg
pic1.jpg (125.08 KiB) Viewed 89 times
pic2.jpg
pic2.jpg (147.54 KiB) Viewed 89 times
by alastair
28 Jun 2022, 12:56
Forum: Hardware and software hacking
Topic: Gigatron Clone Ideas
Replies: 46
Views: 1570

Re: Gigatron Clone Ideas

Congrats! I'm curious... what make/model RF modulator? I got the adapter a few months ago from AliExpress. It's about $20 with shipping - https://www.aliexpress.com/item/3256803136528164.html It's the only "upscaler" I have that will support 120Hz refresh. I also have a cheap Visio TV tha...
by alastair
27 Jun 2022, 15:42
Forum: Hardware and software hacking
Topic: Gigatron Clone Ideas
Replies: 46
Views: 1570

Re: Gigatron Clone Ideas

The board came in Friday but I was still waiting on a couple of components. They just arrived and it worked first time 8-) novatron-lives.jpg CRT via RF modulator for added effect. I don't have a Pluggy installed yet or a Famicom controller to interact with it. Started with the V1 ROM and will progr...
by alastair
22 Jun 2022, 13:47
Forum: Hardware and software hacking
Topic: Gigatron Clone Ideas
Replies: 46
Views: 1570

Re: Gigatron Clone Ideas

I did a quick scan of The V5a ROM to see what Instructions were used That's really helpful. I also noticed 6 instances of "bra [Imm]". Those I could handle, but not the "jmp [Imm]". I agree with @at67 though. Breaking compatibility is a rabbit hole I don't want to go down. I jus...