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Post by minsoft on Jan 26, 2023 12:57:11 GMT -5
I had previously thought access time could be the cause of the issue (for want of a better explanation), but that seems unlikely now that the problem (120ns & 255ns) eproms work with that 32K bridge removed. Although I need to do more testing to be 100% sure of that...
It was suggested to me before to stick to 90ns or below, but I haven't been able to find any < 100ns. The most reliable ones I have been testing with are 200ns so I'm not sure if it really needs to be lower than that, in reality.
If anyone knows of a good supplier (UK preferably) then please let me know!
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Post by minsoft on Jan 26, 2023 12:58:46 GMT -5
Is it loading/saving at the time these issues happen? It seems like it wouldn't be. No, never a problem when loading/saving, random(ish, but reproducible) points.
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Post by playvectrex on Jan 26, 2023 21:42:29 GMT -5
If you'd like to try a faster EPROM, I can confirm these are in fact brand new and as labeled 27C256-70 (70ns) www.amazon.com/gp/product/B06VVJV1XVHave you considered using the flash chip used in Malban's Vectorblade design? You can get them brand new in 70ns and 55ns speeds, and the cool thing about them is you don't need the DS2430A anymore as it can be re-flashed by the Vectrex itself with 5V. Routines in open source Vectorblade ripe for copy and paste (Thanks Malban! ) This is my version of the VB cart, and you really don't need to wire up all four 48K banks if you don't need them all github.com/technobly/vectrex-vectorblade
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Post by minsoft on Jan 27, 2023 4:15:53 GMT -5
If you'd like to try a faster EPROM, I can confirm these are in fact brand new and as labeled 27C256-70 (70ns) www.amazon.com/gp/product/B06VVJV1XVHave you considered using the flash chip used in Malban's Vectorblade design? You can get them brand new in 70ns and 55ns speeds, and the cool thing about them is you don't need the DS2430A anymore as it can be re-flashed by the Vectrex itself with 5V. Routines in open source Vectorblade ripe for copy and paste (Thanks Malban! ) This is my version of the VB cart, and you really don't need to wire up all four 48K banks if you don't need them all github.com/technobly/vectrex-vectorbladeI'm not sure if the Amazon link is opening the right item for me, but it is £39.14 for 2x eproms which seems extortionate!
As for the Vectorblade design...no I hadn't considered doing that. I wanted my first game to be as simple as possible - 32K max, no bank switching. It's too late for me to change that now, the game is basically ready for release and I have all the parts.
I would consider it if I ever make another game though, and your design looks great!
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Post by minsoft on Jan 27, 2023 4:25:53 GMT -5
I was looking through this and it seems pretty common for Vpp to be left unconnected to anything on PCBs equipped with an eeprom:
(see Malban's Karl Quappe & Release, Alex Herbert red PCB, uknown clockworkrobot PCB near bottom of page...possibly 64k)
Perhaps done for a reason?
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Post by kokovec on Jan 27, 2023 12:21:21 GMT -5
In all my years of building stuff for the Vectrex, I've never used one (E)EPROM. Microcontrollers have gotten so cheap that it probably makes more sense to design a cart that uses the built-in flash ROM and EEPROM for game/save data. They can be purchased for under $2 each.
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Post by playvectrex on Jan 27, 2023 12:58:20 GMT -5
minsoft"I'm not sure if the Amazon link is opening the right item for me, but it is £39.14 for 2x eproms which seems extortionate!" Ah... haha... probably because it's a US amazon and shipping from the US. Maybe try searching for something similar locally? "As for the Vectorblade design...no I hadn't considered doing that. I wanted my first game to be as simple as possible - 32K max, no bank switching. It's too late for me to change that now, the game is basically ready for release and I have all the parts. I would consider it if I ever make another game though, and your design looks great!" Thanks! No worries Next time! "I was looking through this and it seems pretty common for Vpp to be left unconnected to anything on PCBs equipped with an eeprom. see Malban's Karl Quappe & Release, Alex Herbert red PCB, uknown clockworkrobot PCB near bottom of page...possibly 64k. Perhaps done for a reason?" I don't think I'd rely on that without some explanation from them. I'd rely on the datasheet and my own testing, but if you can get an explanation and proof of testing (and the EPROM they used), then you can ride on the shoulders of those that came before you kokovec"In all my years of building stuff for the Vectrex, I've never used one (E)EPROM. Microcontrollers have gotten so cheap that it probably makes more sense to design a cart that uses the built-in flash ROM and EEPROM for game/save data. They can be purchased for under $2 each." That would be really cool, but overly complicated for most developers. Not only would you have to learn how to code for the Vectrex, you'd have to learn how to code for whatever micro controller you are using. Micros are still in short supply these days and high priced. The exception is probably RP2040, but I don't think there are any reference designs for Vectrex carts yet with that. I think they are $2 though and require some more components like 3.3V regulator, xtal, etc... This is like making a VEXTREME for every cart you sell... kind of a pain The SST39SF020A can be had for less than $2, and doesn't really need the extra components in the Vectorblade design if you don't need 4 banks. You can use it like a 32K or 64K EPROM if you'd like. I recently bought 50 64K EEPROMs (the electrically erasable kind) from eBay for $44 free shipping. They were used parts, rebranded so look new for the most part, and all but 2 of them were good. So a nice cheap option
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Post by minsoft on Jan 27, 2023 15:02:57 GMT -5
I suppose with hindsight my choice of hardware may not be the best. However being new to this I wanted to use the simplest option. Granted I did not forsee having these issues!
Another bit of info: I looked at the non-DS2430 equipped pcb I was using (not a clockworkrobot one), and that one has Vpp tied to Vcc. So perhaps that partially explains things, and the presence of DS2430 (& associated code) is not relevant. However as the datasheets say Vpp to ground is ok it doesn't explain that.
I've clocked up several hours testing now, on two Vectrexes, various eproms, DS2430, and not had any problems with Vpp left floating...
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Post by kokovec on Jan 27, 2023 16:54:28 GMT -5
kokovec"In all my years of building stuff for the Vectrex, I've never used one (E)EPROM. Microcontrollers have gotten so cheap that it probably makes more sense to design a cart that uses the built-in flash ROM and EEPROM for game/save data. They can be purchased for under $2 each." That would be really cool, but overly complicated for most developers. Not only would you have to learn how to code for the Vectrex, you'd have to learn how to code for whatever micro controller you are using. Micros are still in short supply these days and high priced. The exception is probably RP2040, but I don't think there are any reference designs for Vectrex carts yet with that. I think they are $2 though and require some more components like 3.3V regulator, xtal, etc... This is like making a VEXTREME for every cart you sell... kind of a pain The SST39SF020A can be had for less than $2, and doesn't really need the extra components in the Vectorblade design if you don't need 4 banks. You can use it like a 32K or 64K EPROM if you'd like. I recently bought 50 64K EEPROMs (the electrically erasable kind) from eBay for $44 free shipping. They were used parts, rebranded so look new for the most part, and all but 2 of them were good. So a nice cheap option I understand what you're saying. However, I'm sure that if someone designed a micro based cart, Malban could incorporate the merging of micro firmware with the game data in VIDE. With proper boostrap firmware, I bet a cart can be made where a developer could cryptographically protect their game code for distribution, and not have to bother with building carts.
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Post by playvectrex on Jan 27, 2023 20:43:05 GMT -5
Malban and I have already done this but you need to work outside of VIDE with other toolchains. For like one more dollar in cost though you can have USB and flash storage and a menu with room for 600 games as well... and you basically then have VEXTREME... assuming your $2 micro would work without extra buffers or gates (not sure if it's 5V tolerant). But, we digress! Since you have never used an EPROM (or was that EEPROM?)... what have you been using? EDIT: I should clarify though, Malban and I don't like to encrypt things... just make them open. Also, instead of making it encrypted, you could just read protect the MCU, however you can always read the game data from the cart port just like the Vectrex must be able to. There are ways of tying it to the Vectrex though, but if you are really that worried... your game better be the BEST thing since sliced bread Vectorblade is open source and sold out no problem over and over again. Copies hit eBay for over $1000 while it was open source on Github.
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Post by D-Type on Jan 28, 2023 3:32:32 GMT -5
I reckon using EEPROMs is the way to go, a rewritable cart design would be nice. I don't think encrypting games has a benefit, except for being a fun technical challenge to implement, people aren't pirating carts anyway. As PlayVectrex said, if you're going to encrypt your game, it better be good! I did see a vid from someone who has made a Pico into an EPROM emulator, all it needed was 3 extra 3.3 to 5v level shifters. Cheap, but fiddly.
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