• Please review our updated Terms and Rules here
  • Exhibitor application for VCF West 2022 is now open! If you are interested in exhibiting, please fill out the form here.
  • Here are the results of the VCF East 2022 Post Event Survey: Survey Results

Apple IIe DIY Serial Card?

thenzero

Experienced Member
Joined
Feb 19, 2021
Messages
424
Location
Perry, GA
I know I know. Life and a million projects gets in the way, but it’s still on my workbench. Maybe this weekend.
 

epooch

Member
Joined
Apr 12, 2013
Messages
24
Location
Poway, CA
The EEPROM is probably the most expensive single component.
Jameco Shopping Cart


Part Number, Description, Quantity, Unit Cost, Total
74843,"IC,EEPROM,28C256-15,5V 32kx8,D","5","$12.25","$61.25"
Those are expensive EEPROMs. You can bring the price down a bit by using:
250ns seems slow, but some of the Apple cards have 400ns ROMs, I think.
And AT28c64 EEPROMs are dirt cheap on eBay. 5 for $6.00.
 

bitfixer

Veteran Member
Joined
Apr 6, 2011
Messages
651
Location
San Francisco, CA
You might be able to omit the MAX232 chip, given the high likelihood of using a usb->serial adapter from a modern computer instead of a true serial port. Just a cost saving idea.
 

Eudimorphodon

Veteran Member
Joined
May 9, 2011
Messages
4,427
Location
Upper Triassic
You might be able to omit the MAX232 chip, given the high likelihood of using a usb->serial adapter from a modern computer instead of a true serial port. Just a cost saving idea.

They only cost a couple bucks, and in their capacity as a buffer there's at least a chance they'll throw themselves on top of the landmine and stop a stray short or spark from getting to the more expensive 6551, so... doesn't really seem worth it. (And of course this is on top of limiting yourself to TTL-level serial.)
Those are expensive EEPROMs. You can bring the price down a bit by using:

If you're making your own thing that doesn't specifically require an EEPROM (IE, you're not writing to it in-circuit, you just need a programmable ROM) I would highly recommend subbing a 32 pin socket wired to use an SST39SF010 flash chip. They're dirt cheap ($1.67 quantity one at Mouser) and rated for 70ns so speed shouldn't be a problem on any "antique" computer. (I've used them for video character generators, they work fine for that.) Yes, they're 128K and you're wasting most of it, but just tie those extra address pins to ground and you're good to go.
 

VERAULT

Veteran Member
Joined
Jan 30, 2012
Messages
5,123
Location
Connecticut, USA
i use a true serial device with my ssc so cutting this corner i think would not be worth it. Backwards compatibility is the name of the game.
 
Top