From 473d04d7d99276013ad88f162c983d91248dd63f Mon Sep 17 00:00:00 2001 From: Virgil Dupras Date: Mon, 12 Oct 2020 21:39:53 -0400 Subject: [PATCH] recipes/sms: add cartridge hacking instructions --- recipes/sms/README.md | 38 ++++++++++++++++++++++++++++++-------- 1 file changed, 30 insertions(+), 8 deletions(-) diff --git a/recipes/sms/README.md b/recipes/sms/README.md index e6ec083..a2ad8cf 100644 --- a/recipes/sms/README.md +++ b/recipes/sms/README.md @@ -21,18 +21,41 @@ are other recipes related to the SMS: ## Gathering parts -* [zasm][zasm] -* A Sega Master System or a MegaDrive (Genesis). (I have only tested on a - MegaDrive so far) +* A Sega Master System or a MegaDrive (Genesis). * A Megadrive D-pad controller. * A way to get an arbitrary ROM to run on the SMS. Either through a writable - ROM card or an [Everdrive][everdrive]. + ROM cartridge or an [Everdrive][everdrive]. + +## Hacking up a ROM cart + +SMS Power has instructions to transform a ROM cartrige into a battery-backed +SRAM one, which allows you to write to it through another device you'll have +to build. This is all well and good, but if you happen to have an AT28 EEPROM, +things are much simpler! + +Because AT28 EEPROM are SRAM compatible, they are an almost-drop-in replacement +to the ROM you'll pop off your cartridge. AT28 are a bit expensive, but they're +so handy! For SMS-related stuff, I recommend the 32K version instead of the 8K +one because fitting Collapse OS with fonts in 8K is really tight. + + +1. De-solder the ROM +2. Take a 28 pins IC socket +3. Cut off its WE pin (the one just under VCC), leaving a tiny bit of metal. +4. Hard-wire it to VCC so that WE is never enabled. +5. Solder your socket where the ROM was. +6. Insert Collapse OS-filled EEPROM in socket. + +As simple as this! (Note that this has only been tested on a SMS so far. I +haven't explored whether this can run on a megadrive). ## Build the ROM -Running `make` will produce a `os.sms` ROM that can be put as is on a SD card -to the everdrive or flashed as is on a writable ROM cart. Then, just run the -thing! +Running `make os.sms` will produce a `os.sms` ROM that can be put as is on a SD +card to the everdrive or flashed as is on a writable ROM cart. Then, just run +the thing! + +To run Collapse OS in a SMS emulator, run `make emul`. ## Usage @@ -64,4 +87,3 @@ seconds. It's the emulator's fault. On real hardware, it's not as slow. [smspower]: http://www.smspower.org [everdrive]: https://krikzz.com -[zasm]: ../../tools/emul