CannibalCat Posted February 10, 2014 Share Posted February 10, 2014 Hello, just made a 32k Linear RAM cart yesterday for my DevOS 0.2 modded 7800. I am able to dump carts no problem so I think my HW setup is valid, sending binaries to the new cart seems to work fine as well (sent a 32k binary and it copied successfully), after uploading to the 7800 it goes back to the DevOS menu (as it should), I choose "Play 7800 game" and hit reset but I just get a black screen. I'm wondering about the placement of R1 and C2 as required by the instructions, maybe I have something wrong? Anyone ever run across these symptoms? I attached a pic of the cart. Plans were from: http://www.oocities.org/gjp57/devcarts.pdf Quote Link to comment Share on other sites More sharing options...
Eckhard Stolberg Posted February 10, 2014 Share Posted February 10, 2014 Can't help you with the hardware, but did you try reading back your binary after you have transferred it to the RAM cart? If it's not the same as the data you sent, this might help you figure out where the problem is. Quote Link to comment Share on other sites More sharing options...
CannibalCat Posted February 10, 2014 Author Share Posted February 10, 2014 Eckhard, I'll give that a shot tonight... that's a good idea. One other question: Do I need to use a78sign on the binary before I send it over (after assembly), or is that just for burning EPROMS? Quote Link to comment Share on other sites More sharing options...
CPUWIZ Posted February 10, 2014 Share Posted February 10, 2014 The cap and resistor look fine, on DevOS, you shouldn't need to sign the binary. It's hard to tell from the picture, but is it possible that the bridge between chip select and output enable is touching A10? Quote Link to comment Share on other sites More sharing options...
CannibalCat Posted February 10, 2014 Author Share Posted February 10, 2014 CPUWIZ, yeah the top down pic is misleading, pins 20 and 22 are bridged and quite elevated away from pin 21... but I'll double check everything when I get home, could be a short somewhere I suppose. Quote Link to comment Share on other sites More sharing options...
CannibalCat Posted February 11, 2014 Author Share Posted February 11, 2014 Well, something is definately amiss... tried to read back the binary and 7800ctrl thinks it's a 48K cart with 16K to transfer... maybe an address line issue? I need a magnifying glass! When is that Harmony 2 cart coming out?? Quote Link to comment Share on other sites More sharing options...
Eckhard Stolberg Posted February 11, 2014 Share Posted February 11, 2014 The cartridge type auto detection can't detect how big the binary is that you transferred to the RAM cart. Also it works best when the 7800 has just been turned on. So in your case it's quite possible that a 32K RAM cart gets detected as a 48K cartridge. That's not indicating a problem with your RAM cart. If the binary that you transferred t the 7800 is 16K, then you need to use the -t7816 command line option when you read it back. Quote Link to comment Share on other sites More sharing options...
CannibalCat Posted February 11, 2014 Author Share Posted February 11, 2014 Eckhard, it was a 32k binary, I tried transferring it as 7832 and also as "TEST" (the autodetect). When I went to copy it back, I'm pretty sure I chose 7832 as well. I'll double check tonight. Also need to go over the pins with a fine tooth comb. Quote Link to comment Share on other sites More sharing options...
gpercy Posted July 13, 2014 Share Posted July 13, 2014 Hi CC, bit late comining in on this, and you may have figured it out already. ;o) Your cart looks fine. Take a look at devcarts.pdf page 4, note 7 for 32K cart. Requires "7800ctrl -c1 name.bin" when uploading using latest 7800ctrl.exe since default cartridge type is assumed to be bankswitching type (-c0). Without -c1 switch your upload will be copied as two 16K blocks over the same memory space ---> fail regards... Graham.P Quote Link to comment Share on other sites More sharing options...
gpercy Posted July 16, 2014 Share Posted July 16, 2014 BTW, the version of 7800ctrl.exe which I am using is dated 29th Nov, 2002 (appears upper right of screen when executing without any command string). cheers ... Graham.P Quote Link to comment Share on other sites More sharing options...
CannibalCat Posted July 21, 2014 Author Share Posted July 21, 2014 Graham, thanks for the tips... I will try it out again tonight when I get home. I never did get it to work and ended up building an EPROM cart (w/Pokey) instead, works fine but a pain to erase/burn when I want to try on the real HW! Quote Link to comment Share on other sites More sharing options...
CannibalCat Posted July 21, 2014 Author Share Posted July 21, 2014 BTW, the version of 7800ctrl.exe which I am using is dated 29th Nov, 2002 (appears upper right of screen when executing without any command string). cheers ... Graham.P This later version of 7800ctrl did the trick! Now it transfers all 32K but when I select "Play 7800 Game" from the DevOS menu and hit RESET, black screen... isn't that the correct procedure? Quote Link to comment Share on other sites More sharing options...
gpercy Posted July 24, 2014 Share Posted July 24, 2014 Hi CC, yes, that's the correct procedure. I've looked again at your photo and think I can see an error. The cap at C2 appears to be connected between gnd and A14 instead of +5v. The uppermost connection is soldered to the incorrect point. C2 should go from gnd to +5v which is a solder point hidden under the upper end of your cap. Check it out. Also, be sure that CE/OE are wired to pin #13 on U3 (not pin #14, not quite clear in photo). Otherwise, check through all troubleshooting tips in devcarts.pdf at the end of page 8. Then, otherwise, try a small binary such as a 264K which has the best chance of working. cheers .... Graham.Percy Quote Link to comment Share on other sites More sharing options...
SIO2 Posted February 13, 2015 Share Posted February 13, 2015 (edited) I have one of these RAM carts that I did not build and can not test because I do not have a Dev Os modified system yet. I hope to have one in the near future. BTW is someone sellig the Dev Os. roms? I was reviewing the instructions for building a 32k ram cart (devcarts.pdf rev 14/2003) which says to "ensure that R1 and C2 are fitted." Comparing the RAM cart I have with an unmodified 7800 Cross Bow cart, it appears whoever built the RAM cart moved the cap from its default position to the C2 marker (see photo, RAM cart on top, Cross Bow on bottom). Which position should the cap be in for the RAM cart? Edited February 13, 2015 by SIO2 Quote Link to comment Share on other sites More sharing options...
CPUWIZ Posted February 13, 2015 Share Posted February 13, 2015 The power smoothing capacitor, should be across VCC and GND. 1 Quote Link to comment Share on other sites More sharing options...
SIO2 Posted February 13, 2015 Share Posted February 13, 2015 (edited) The power smoothing capacitor, should be across VCC and GND.Thank you. That helped. According to the data sheet for the AS7C256-20PC SRAM and the pinout for the 7800 cartridge port, the cap should have remained in the factory position. I will have to move it back. The way this board is marked, I can see why someone was confused by the instructions. Edited February 13, 2015 by SIO2 Quote Link to comment Share on other sites More sharing options...
SIO2 Posted February 23, 2015 Share Posted February 23, 2015 (edited) I now have a DevOs .2 modified 7800. It seems to work to dump carts as I have dumped Space Invaders and the resulting .bin worked in the Stella emulator and also played on the DevOs 7800 when placed on a Harmony cart. However, when I try to upload to the DevOs system 32K ram cart with cap moved to factory position, it says the transfer was done but the game doesn't work. I am using a Windows 98SE laptop booted in dos mode for all transfers down and up. I have tried the version of 7800ctrl.exe included on Eckhard's website with release 2. I have also tried the 78ctrl38.exe version with the -c1 switch. No luck. Results have varied depending on what I tried to upload from black screen to vertical monochrome color bars to multicolor rolling patterns. My laptop parallel port options are ECP and standard bi-directional. I have tried both and it didn't seem to make a difference? I tried uploading a 2k game splatform 1.01 with switch -w1800 and it transferred but did not run. I tried uploading it with the ram cart in slot and without a ram cart inserted. Did not work either way. I assume no cart would be needed for this case? Is there a chance this 7800 has faulty internal ram? My goal is to be able to upload 7800 homebrews for testing on the real hardware. Any thoughts or advice on what I might try to make this work are greatly appreciated. Edited February 23, 2015 by SIO2 Quote Link to comment Share on other sites More sharing options...
SIO2 Posted February 24, 2015 Share Posted February 24, 2015 This 7800 that I am having the trouble with uploading does not have the 74LS02, cap 65 or R66. I understand that some people remove these to improve compatibility with 2600 games but this unit never had those parts installed. Would this have any impact on uploads? Quote Link to comment Share on other sites More sharing options...
SIO2 Posted February 24, 2015 Share Posted February 24, 2015 I noticed that Eckhard's instructions with release two say that you could test a small upload without a ram cart and to use -w2000 switch. I tried uploading splat.bin with the -w2000 switch. I get a timeout error. If I upload splat.bin with -w1800 the transfer completes but the game does not run. Quote Link to comment Share on other sites More sharing options...
SIO2 Posted February 24, 2015 Share Posted February 24, 2015 Solved. I modded another 7800 mobo (REV A) and put the DevOs eprom in. So far I have dumped and uploaded and played 2600 frogger, 2600 space invaders and 7800 centipede using the same laptop PC, cable and 32k linear ram cart. So, there is a problem with the other 7800 mobo. The problem is not the missing 74LS02 timing circuit because the working REV A board doesn't have it either. Perhaps bad ram though the mobo rams were not getting hot. I'll have to work on that later. Right now, I am going to play centipede from ram cart. Quote Link to comment Share on other sites More sharing options...
Like us on Facebook
Follow us on Twitter
AtariAge on Instagram
Watch us on YouTube
Chat on Discord
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.