[HH] arduino questions?

[John Luciani]

Sorry for the late reply but I just learned about the list yesterday :)
Not sure how to reply to a message in the archive.

[Q1] The "5V" pin is the "VCC" pin. It is connected to the VCC of the uC.
For some boards this is 5V (or a little less). For a lot of boards (like my
wiblocks boards) this is 3.3V. The voltage will be constant during
programming.

[Q2] I program all my parts using the ICSP. An oscillator is not required.

[Q3] You can run the ATmega168/328 at frequencies up to 20MHz. However,
the maximum frequency is dependent on the VCC you use for the
microcontroller.
There is a frequency derating curve in the datasheet.
I believe the reason that the Arduino is run at 16MHz is to give some
margin with
the VUSB + LDO dropout. I run my boards at 3.3V and 12MHz.

The CPU frequency is set in the Makefile using the F_CPU variable. You will
not
have problems with most of the code. However, there could me some libraries,
like NewSoftSerial, that could have nested if/then/else clauses that do not
examine the F_CPU for the frequency you choose. I had a customer who
wanted to use NewSoftSerial with his wiblocks board. After calculating the
new timing constants I was able to modify NewSoftSerial to work at 12MHz.
See http://wiblocks.luciani.org/docs/app-notes/software-serial.html

(* jcl *)


-- 
http://www.wiblocks.com
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