Programming info for GeneralPlus 6502 devices? - Page 1
Forum section: electronics / general

author: david.given
author_rank: Contributor
timestamp: January 25, 2022, 11:25:32 pm
content: I found a VTech toy laptop in a junk shop and pulled it apart to see what made it go.What makes it go is a blob processor wired up to a 8-pin SPI flash. After removing the flash and dumping it, I discovered that the blob implements a 65c02 CPU with memory-mapped SPI memory. I track down enough of the boot process to make my own ROMs and by using a signal analyser to watch the SPI memory access I can determine that my program ('BRA $') is actually running. I've successfully managed to dump part of the internal ROM, which contains all the fun stuff for managing SPI ROM banks and I/O; I just need to figure out what it's all doing now.I don't actuallyknowthis is a GeneralPlus device but it seems a plausible guess. They have a wide variety of products on their web site which almost match this one --- LCD dot matrix controller, polyphonic audio, ADPCM decode, etc. Unfortunately their datasheets are terrible and contain very little actual information. The best info I've found is from a Tamagotchi hacking project from about 2010 based on a GPLB5x, but this device seems different (memory map doesn't match the one in their device).Does anyone know of any sources that have been collecting info on these chips? Even something that's nearly but not quite the same as mine will be useful, assuming similarity between devices.Thanks!

author: brucehoult
author_rank: Super Contributor
timestamp: January 26, 2022, 01:00:43 am
content: Wow, that's kind of cool. Any idea of the clock speed? Or original price?A Cortex M0 or tiny RISC-V would be superior in every way. Or even an AVR if it's running fixed code.But cool.

author: amyk
author_rank: Super Contributor
timestamp: January 26, 2022, 02:14:24 am
content: If you have the model number you may be able to find an FCC emitted radiation conformance report, which could contain more details about the electronics.

author: david.given
author_rank: Contributor
timestamp: January 26, 2022, 10:37:58 am
content: Judging by the other GeneralPlus devices it's probably 8MHz. I don't know how much slower it will be running code from SPI flash --- I haven't bothered to measure it yet. But yeah, it's a surprisingly cool device. It's probably got about 2kB of RAM, which is enough to run reasonable programs from. It's got a load of exposed I/O lines for the keyboard; I'm hoping these will turn out to be wired directly to GPIOs. The only tricky bit is having to take the surface mount flash chip off and replace it with a socket (or in my case two rows of carefully bent header sockets).You can still get these new for about 40 currency units? But they show up in junk shops all the time, at least where I am, and there's a huge range of very similar models which I'll guess all use the same architecture. Some of them have real qwerty keyboards!I found a video of the English version in action:

author: brucehoult
author_rank: Super Contributor
timestamp: January 26, 2022, 11:59:28 am
content: Aha. I see those are available for about NZ$44 (or AU$34 in aussie stores) though a lot of places are out of stock.It must have quite a lot of ROM (flash) in it.

author: david.given
author_rank: Contributor
timestamp: May 22, 2022, 10:31:20 pm
content: It's been a while, but I've made progress!

author: ebclr
author_rank: Super Contributor
timestamp: May 23, 2022, 02:42:53 am
content: Take a lookIt's not directly related, But is interesting alsohttps://github.com/Klapautsiy/6502_EhBASIC_ESP32_Arduino