AVR-Chat

On Jan 29, 2012, at 11:09 AM, Chuck Hackett wrote:

> My other regret Is that I violated a rule I should have known - use the
> device with the largest reasonable amount of memory available to reduce the
> chances of "hitting the wall" in development. Even though this was my first
> real microcontroller-based design, I should have known better ... (see my
> signature line!).
> 
> My board is designed around the ATMega32A and I am about at its memory
> limits (with optimization turned on) and I have more features to add
> (naturally). I would like to upgrade to the largest compatible processor
> that:
> - 5v supply
> - TQFN-44 package
> 
> Pins/peripherals I'm using (from memory without detail checking of the
> code):
> - 8 A/D inputs
> - SPI
> - TWI
> - 1 UART (diag & monitoring)
> - JTAG
> - OC2
> - INT2
> - AREF
> - 6 general I/O
> - Timers 1&2
> - 14.7456 Xtal
> - Watchdog
> 
> I have checked the data sheets and it looks to me like I can choose from the
> following:
> 
> ATMega644, 644P, 644PA, 644A
> ATMega1284 & 1284P
> 
> Mouser does not seem to stock the ATMega1284x in TQFN-44 but DigiKey stocks
> the ATMEGA1284P-AU-ND which would seem to fit the bill.
> 
> For my use is the ATMEGA1284P-AU-ND pin and software (with appropriate
> changes in defines, etc.) compatible the ATMEGA32A-AU or am I missing
> something?
> 
> 
I hit the wall using the ATMega 32 (on a model railroading project), went looking and chose the ATMEga1284P.  Software and hardware wise it was a drop in replacement.  The only thing I had to do to use the new chip was change the settings in my make file.  

The 1284 has more RAM, Flash and EEPROM and it has an additional timer and serial port.  In that project I did make use of the additional timer but not the serial port.

I don't know if the 1284 you are looking at is pin compatible with the 32 you are using but I suspect it is.

When I started using the AT AVRs I had settled on a few parts to use.  I hadn't looked around since then and wasn't aware of the 1284.  My biggest pet peeve is the large number of parts and the trouble of selecting one from that pool.  I just wish I had this sort of problem with other things.
> 
> 



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