Arduino as ISP, Why not an ATmega168

I accidently ordered a couple of of extra Nano with ATmega 168 mpus.

I was thinking of useing one as a ISP using the "ArduinoISP.ino" sketch.
I note the MIT documentation says:
Arduino Uno or Duemilanove (w/ an ATmega328, not an older board with an ATmega168).

Why not an ATmega168 ???

Imagin lack of memory, SRAM or flash.

Grumpy_Mike:
Imagin lack of memory, SRAM or flash.

The ATmega168 has 1K SRAM and 16K of FLASH.

The compiled sketch is just over 5K:
Binary sketch size: 5,492 bytes (of a 14,336 byte maximum)

Writes to the FLASH are done 0ne page at a time. SRAM is used to catch the FLASH pages.
Ref Atmel AVR109, http://www.atmel.com/images/doc1644.pdf
The Flash memory is divided into pages containing 32, 64, or 128 words each.

I imagine it has enough memory but I have been wrong before.

SRAM is used to catch the FLASH pages.

Only when you are running a self programming program. The the "ArduinoISP.ino" sketch is not a self programming program.

It looks like it is the lack of SRAM that is stopping you using a 168. I haven't looked at the code but I would expect there to be a call for bigger buffers. SRAM has to hold all program variables and buffers as well as the stack.

Grumpy_Mike:
Only when you are running a self programming program. The the "ArduinoISP.ino" sketch is not a self programming program.

It looks like it is the lack of SRAM that is stopping you using a 168. I haven't looked at the code but I would expect there to be a call for bigger buffers. SRAM has to hold all program variables and buffers as well as the stack.

"I haven't looked at the code ...",
I have but it was not written with a lot of helpful comments.
Probably much more meaning for someone who is intimate with the entire process.

I also have Nic's "Atmega chip programmer" ... has quite a few more comments.
I might be able to muddle through that one.

I am going to try it anyway. I ordered a couple Atmega328's and ATiny45's to play with.
Worse case senario I am out a $7.00 nock off Nano.
(I ordered these figuring I might blow something up and I did not want it to be a premium board).

Best case is I have a $7.00 ISP programer with some extra pins.

More likely it does not work and I build a dedicated programer using one of the "play" chips I ordered.
Of course then I have to find another way to blow up the spare Nanos. ]:slight_smile: