Adding an expansion port (game cartridge port) to the propeller

TonyA

Wondering if it would be difficult to add an expansion port to the propeller chip, like the one used on the Hydra. I would only be using it as an external·eeprom.

How would I proceed?

Thanks.

Mike Green

What kind of external EEPROM do you have in mind? If you want to use additional I2C EEPROM it can just be connected to the existing pins used for the boot EEPROM. You can attach a total of 512K made up of 24LC512 (64K) devices to those two pins. You can also attach more sets of 512K to other pairs of pins with standard I2C pullups on the two pins. Existing I2C EEPROM I/O routines will work with multiple sets.

Atmel sells large flash memory devices up to several MB in size that will interface to a Propeller via 3 or 4 I/O pins using the SPI protocol. Someone had posted some I/O routines, but I don't have the link. You can also use an SD card using Rokicki's FAT16 drivers.

TonyA

Hi,

Just brainstroming, and wondering how I might use a Hydra expansion game card (i.e. 128k expansion card) with the propeller educational kit.

Looking for the easiest way to load a Spin application onto a propeller chip using the Hydra eeprom card. *Or using a homemade eeprom card (which doesn't have to be 128k, I only really need 32k).

I am currently experimenting with the Hydra, but eventually I want to make a very simplified version of the Hydra, just using a propeller chip, gamepad port (female edge connector as on the Hydra), (plus the other vitals).

Thanks for any insight.

Post Edited (TonyA) : 7/7/2007 8:51:25 PM GMT

TonyA

If using the serial eeprom 24LC256·would I·just connect the epprom to Prop pins P28 and P29? Would that be all I need to do? (Besides power and ground).

Thanks.

Post Edited (TonyA) : 7/7/2007 11:16:00 PM GMT

Paul Baker

Tie A0 to Vdd and A1 and A2 to gnd (Vss).

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.

TonyA

Cool, thanks.

TonyA

I am noticing however, in the Hydra book the schematic diagram for the 24LC256 pg. 164 (for both the onboard eeprom and the expansion card eeprom) that A0-A2 go to ground.

Would I not need to bring A0 high if I were using the eeprom on a removable card that is automatically detected by the Propeller? I'll be just using it·for simple storage.


(The onboard eeprom of the Hydra shows A1 being used to provide a "loop back" signal, but I wouldn't need the "loop back" option. So I would assume A1 would also go to ground in my case).

Paul Baker

If you are putting it on the same I2C bus as the existing EEPROM you need to give it a different address than the one that is already there you you can individually address it.

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.

TonyA

(My apologies in advance, in case I am confusing this.)


I want to make a simple eeprom card to connect to the Propeller. It would be the only eeprom used by my propeller chip. So I guess I would not have to·connect A0 to Vdd?


Thanks again for you help, I appreciate it.
Tony

Post Edited (TonyA) : 7/8/2007 7:30:00 PM GMT

Paul Baker

Correct, I was thinking you wanted to expand memory, not replace it. You will have to devise a means for blocking the original EEPROM (like what is done on the hydra) so there is no interference.

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.

Mike Green

Most but not all EEPROMs have circuitry on their address select and write protect inputs that will treat an open connection as a connection to ground. It's better design practice to always connect an unused input to either ground (Vss) or the supply voltage (Vdd).

TonyA

Right, sorry I didn't explain that better. But I'm not trying to expand eeprom, just replace the eeprom you would normally use on your breadboard (with a female edge connector and a simple pc board with the 24LC256 stuck in it.)


What I'd like to do is just taking a single (no accessory) propeller chip and connect it to a diy card with an eeprom on it. It would be the only, single eeprom used with my propeller chip.

Like the Atari 2600 cartridge, except I could erase and re-program mine.

Thanks again. (I'm starting to understand, I appreciate it)