My hardware project :: GCart 2011

[TLovskog]

Hi,

No. Not Junior. It is by design quite limited. It should be seen as a low cost RAM expansion with the possibility to have 15-63 custom cartridges.

I do this mostly to test the programmable logic. This is a series of components I right now are going to use professionally, so junior was a very good test vehicle for it.

It was also a test to see how cheap I could do a reasonably useful and configurable cart.

Junior can have ...

• 8 different configurations; Stock, 3k, 24k, 27k, 27k + RAM at BLK5, 27k + RAM (Write protectable) at BLK5, Stock + FLASH at BLK5, 27k + FLASH at BLK5.

• You can also have RAM at IO2&3.

• 15, 31 or 63 banks of FLASH. The Carts own FW uses one bank

The FW is for configuration and flashing.
The configuration is entered with a long press of the reset button, and exit and save configuration with a short press.

Limited. Super simple. Low cost.

The real cartridge. Will however, do that and more. The 8Mbyte memory will be bankable to any bank individually as well as write protected.
It will also have the same programmable logic for BLK selects and timing.

[TLovskog]

Mr Senior Cartridge has come a bit forward. It's main component is a 32bit MCU STM32F722 from ST and a 64Mbit DRAM from Windbond.

The MCU simply emulates the Flash and RAM in software. This gives every possibility to do some fancy stuff besides the obvious and standard features of a ram expansion.

To time this well I also have one of these cheap programmable logic components as in junior. Here we use extensive use of the delay lines to skew the interrupt to the MCU just at the right time so once the interrupt service routine has done all its housekeeping the adress and data is available. Every cycle counts.

Having a MCU also creates the possibility to have a SD card for all programs as well as BLE and WiFi (the larger unpopulated module). There is also a back-up RTC.

[brain]

Does the ARM automatically connect to the DRAM and handle refresh, or do you implement your own refresh scheme?

Jim

[TLovskog]

Yes. All STM32 has a memory management unit / controller. All can handle Flash memory, Static RAN as well as QSPI SD cards. Some, as with the STM32F722, can also handle dynamic memories natively and automatically.

From the MCUs and the programs perspective these 8Mbyte of memory is one long linear mass of memory.

The SD card is in a similar way also mapped as ordinary memory. All the QSPI calls are handled in the background. Although with the limitation that the window into the SD card is maximum 256M.

/Lövskog

[beamrider]

Really looking forward to the Senior version of this. I have some ideas about utilising the Wifi functionality. Put my name down for one as soon as you have any units available to early adopters.