Doomulation
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Probably means you have implemted a bad instruction somewhere. This is a common case for errors such as these.|\/|-a-\/ said:
Chip 8
- Thread starter sammyboy
- Start date
Doomulation
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Fonts are basically just data stored in the memory. When the instructions says to point to a font, I is set to the address. When the draw function is called, it will draw out fonts from the data. Check out a source of an emulator to see how the fonts are done. It's quite easy.
refraction
PCSX2 Coder
|\/|-a-\/ said:
by use of logical thinking and a good debugger, also trying a few different things is always a good idea.
as for your bug, my mind is telling me to look at your BCD code, its possible that isnt storing the figures correctly, altho i could be wrong.
Doomulation
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I catched most bugs in the emu by stepping thru a debugger. I could catch when the invalid value was written to a register. If you're too lazy to write an own debugger, there are sources posted here that has debuggers, which you may use.
ChaosBlade
My Heart Chose.. Revenge.
What does a debugger do really ?
It looks like a simply fetching opcodes and writing what they should do somewhere. like, "Oh, I saw opcode 8XXX At 0xTHIS address, should copy 01 to Register V[1]."
It looks like a simply fetching opcodes and writing what they should do somewhere. like, "Oh, I saw opcode 8XXX At 0xTHIS address, should copy 01 to Register V[1]."
refraction
PCSX2 Coder
ChaosBlade said:
that basically sums it up yes ;p
for example you could say
"i saw opcode 0x8xxx which is an add command, took x from vx and y from vy, result given was z in vz"
then you can see if the result was correct to the original values or whatever.
its very handy tho for keeping an eye on program jumps and subroutines to make sure they are being executed correctly as well.
Doomulation
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Look at it this way... you KNOW that the value ending up in the register is 0x20. But it SHOULD NOT be that way. So, using a debugger, you step thru the code and notice that HERE it moves 0x20 to the register. So, HERE something is wrong.
That's a basic example of what a debugger does. Of course, it can do so much more. A debugger is a tool to HELPS you find the info you need. For example, it can break whenever a specific value is written to a register. It's pretty much what you code it to be.
That's a basic example of what a debugger does. Of course, it can do so much more. A debugger is a tool to HELPS you find the info you need. For example, it can break whenever a specific value is written to a register. It's pretty much what you code it to be.
hap
New member
I've made a BMP viewer for chip8/s-chip. It'll only work with monochrome bmp's of course, and you'll have to chop the header off. change 00ff to 1202 at offset 0 for chip-8 resolution bmps. See attachments.
as for my emulator, fish n chips, it has had some new versions since i posted it on here (several pages back). main additions are sound, able to change colours, and a rewind feature. you can get it at my homepage: http://hap.samor.nl/
*edit* url changed (and again)
as for my emulator, fish n chips, it has had some new versions since i posted it on here (several pages back). main additions are sound, able to change colours, and a rewind feature. you can get it at my homepage: http://hap.samor.nl/
*edit* url changed (and again)
Last edited:
MobiChip8
I'm currently writing a CHIP8 emulator for cellphones in J2ME (Java for mobile devices). The emulator (which I have ever so cleverly dubbed MobiChip8) is working OK, I've yet to add sound and SCHIP8 capability, but I have some problems to sort out first.
The emulation speed seems fine, that is games play at what feels like a correct speed (my implementation of delay should be OK) but input repetition seems way too fast for some games. Say you try playing "Tetris". When you press "4" (or whatever button it was) to rotate the block, it rotates many times in the splt second before you release the button. Same with "Hidden" (as seen in one of the screenshots), the cursor always moves to the extremes.
I think I've implemented the input handling correct by setting 1/0 in the key registers upon press/release, what more is there that could be wrong? Is it just that the author of the game forgot to set up correct delays?
Anyways, some screenshots from MobiChip v0.5 running in the Sun WTK emulator (but it works perfectly on my Nokia 6630 aswell):
I'm currently writing a CHIP8 emulator for cellphones in J2ME (Java for mobile devices). The emulator (which I have ever so cleverly dubbed MobiChip8) is working OK, I've yet to add sound and SCHIP8 capability, but I have some problems to sort out first.
The emulation speed seems fine, that is games play at what feels like a correct speed (my implementation of delay should be OK) but input repetition seems way too fast for some games. Say you try playing "Tetris". When you press "4" (or whatever button it was) to rotate the block, it rotates many times in the splt second before you release the button. Same with "Hidden" (as seen in one of the screenshots), the cursor always moves to the extremes.
I think I've implemented the input handling correct by setting 1/0 in the key registers upon press/release, what more is there that could be wrong? Is it just that the author of the game forgot to set up correct delays?
Anyways, some screenshots from MobiChip v0.5 running in the Sun WTK emulator (but it works perfectly on my Nokia 6630 aswell):
zenogais
New member
Chip8 emulation will always run rather fast, I'd say you should try putting a delay of some sort on your key input, or setting the value manually to zero after checking it and requiring they repress the key to perform another flip. Not sure if the last one will work, but its worth a try 
Doomulation
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Timing on chip8 is a mystery and a problem...
hap said:
Yeah, it seems the problem is that the CHIP8 only has a virtual CPU not running at a fixed frequency, and the gmaes programmers have targeted different speeds. Maybe I'll hardcode some speed/delays associated with each ROM you can load, as I already have to add different mappings for the controls for each ROM, I might aswell add some more...
zenogais
New member
If you're going to go that route you might as well create an XML file format for individual ROM control and speed configurations based on message digests of the files and using Java's XML parsing facilities to deal with it. It would be a nice, extensible way to do it and you wouldn't have to recompile the file to add configurations.
Doomulation
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Looking forward to if you do that I think other emulators can use that info as well
I think other emulators can use that info as well hey
my first post here... anyhows i found some great info in this thread, and lead me to make my first emulator my chip8 emulator took only a day to make. I'm not releasing it yet, but plan to... atm it runs too fast, and i found a lil bug i have not begun to try and isolated and figure out yet. but for now im moving onto a gameboy emulator <- me think GAMEBOYS ROCK!
I want to thank you all for what i have learnt here, I always thought making an emulator was out of my league, even though I already knew x86 ASM (enjoy doing alot of reverse engineering / cracking)... and been programming for quite some time. but everything made sense and seemed quite simple after browsing over these forums.
now to any new comers, here are the resources i found most useful for making my chip8 emulator. THESE DOCS rocked! CHIP8.htm AND chip8def.htm AND also managed to track down a copy of the GoldRoad Chip8 article chip8.shtml <- which was great! AND finally I found ChoasBlade's source code SOOO EASY to understand, it ROCKED! <- i had to actually force myself not to look at it so I could figure things out for myself get it here ChaoC8 v0.5.zip <- i also kinda ported your (ChoasBlade) emu to use OpenGL, as i was trying to get my emu going and wondering if my OpenGL drawing code was working right.
anyhows I shell be gone now, and try and stay motivated to get my Gameboy EMULATOR DONE!!!
cyas
my first post here... anyhows i found some great info in this thread, and lead me to make my first emulator
my chip8 emulator took only a day to make. I'm not releasing it yet, but plan to... atm it runs too fast, and i found a lil bug i have not begun to try and isolated and figure out yet. but for now im moving onto a gameboy emulator <- me think GAMEBOYS ROCK!I want to thank you all for what i have learnt here, I always thought making an emulator was out of my league, even though I already knew x86 ASM (enjoy doing alot of reverse engineering / cracking)... and been programming for quite some time. but everything made sense and seemed quite simple after browsing over these forums.
now to any new comers, here are the resources i found most useful for making my chip8 emulator. THESE DOCS rocked! CHIP8.htm AND chip8def.htm AND also managed to track down a copy of the GoldRoad Chip8 article chip8.shtml <- which was great! AND finally I found ChoasBlade's source code SOOO EASY to understand, it ROCKED! <- i had to actually force myself not to look at it so I could figure things out for myself
get it here ChaoC8 v0.5.zip <- i also kinda ported your (ChoasBlade) emu to use OpenGL, as i was trying to get my emu going and wondering if my OpenGL drawing code was working right. anyhows I shell be gone now, and try and stay motivated to get my Gameboy EMULATOR DONE!!!
cyas