Go Down

Topic: BASIC Computer Board Design (Read 982 times) previous topic - next topic

James C4S

If you're really serious about making a BASIC interpreter with stuff like motors, sensors, SD cards and such, maybe you should consider something other than the ATmega328.

Why not use the ATmega2560?  You'll start out with 8K of RAM (2X the original Apple I) and it supports extending the RAM with an external chip.   Maybe don't add the external RAM on the first board, but add it later on.

You'll have I/O for your on-board stuff with plenty left over for the user to do whatever they want.  The overall design isn't much more complicated than the ATmega328, though the PCB layout is a little bit more important given the chip's package.

Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

CrossRoads

SD cards need couple hundred mA of 3.3V VCC and 3.3V level signals. 74HC4050 commonly used for  level conversion.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

Totara

Thanks for that, working on it now. My ultimate goal with this is to migrate from using the Arduino Bootloader to having no bootloader.

Totara


If you're really serious about making a BASIC interpreter with stuff like motors, sensors, SD cards and such, maybe you should consider something other than the ATmega328.

Why not use the ATmega2560?  You'll start out with 8K of RAM (2X the original Apple I) and it supports extending the RAM with an external chip.   Maybe don't add the external RAM on the first board, but add it later on.

You'll have I/O for your on-board stuff with plenty left over for the user to do whatever they want.  The overall design isn't much more complicated than the ATmega328, though the PCB layout is a little bit more important given the chip's package.




The motor driver and servo stuff was more of a idea, not really serious. I would prefer to make the board work for the 1st revision, then add the ATMega2560 in a 2nd revision.


SD cards need couple hundred mA of 3.3V VCC and 3.3V level signals. 74HC4050 commonly used for  level conversion.


Thanks for that CrossRoads

CrossRoads

So why just load your sketch with an AVR ISP using File:Upload Using Programmer? Not far to migrate.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

Totara


So why just load your sketch with an AVR ISP using File:Upload Using Programmer? Not far to migrate.


Sorry, I don't quite get what you mean there. Are you suggesting I remove the 6 pin header and only use the ISP header for programming?

CrossRoads

What I meant was:
"So why not just load your sketch with an AVR ISP using File:Upload Using Programmer?"
Left out a word.
Keep the ISP header for loading future versions of the sketch.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

Totara

Hi guys,

I cant believe I forgot this part, a RTC!

http://www.ladyada.net/images/logshield/logschemv1.png

That schematic has a RTC and the same SD card reader as me, will copying it work?

Thanks,
Totara

Graynomad

Yes I think so, if the card holder is the same.
______
Rob
Rob Gray aka the GRAYnomad www.robgray.com

CrossRoads

Yes. Use this brand of '125
http://www.digikey.com/product-detail/en/74AHC125S14-13/74AHC125S14-13DICT-ND/4505054
Has 5V tolerant inputs when powered from 3.3V.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

Go Up