CrossRoads:
What part of the Arduino functionality would you like to keep?
At a minimum you need:
the '328P
16 MHz crystral
two 22pF caps
100nF caps on VCC, AVCC pins
using analog? need 100nF cap on the Aref pin
10K reset pullup resistor
diode such as 1N4158 across the resistor (anode to reset pin, cathode to Vcc)
optional:
Header pins to connect FTDI Basic/FTDI cable, and 100nF cap to connect to Reset pin
or
header pins to connect to ICSP header for rebootloading or for installing bootloaderless sketches
place to connect 5V wallwart, or a battery, or a 5V regulator
Here's an example for a ATmega1284P type board, a '328P would use a smaller connector
This one has both FTDI and ICSP headers, but does not have the diode.
It has screw terminal for bring in 5V power from a wallwart or 4.5V from a triple-AA battery pack (I've used both)
Your idea seems like what i am looking for. basically what i am wanting to do is make a unit that uses the atmega328 chip as the brain so i need all the outputs but dont need all the other things like the serial com or all of the analogue inputs. all i need is the I/O pins. could you please help with a schematic of your board or if you could help with exactly what i need?
Thanks
kylem:
Would i not be able to use the ATmega328 with the bootloader loaded?
Yes. You can use a Mega328 (28 pins), a Tiny2313 (20 pins), a Tiny84 (14 pins), a Tiny85 (8 pins)... whatever suits your requirements. All of them will work with no external components (although it's a good idea to put in at least a decoupling capacitor).
Bootloaders are optional. In fact I don't recommend them for bare chips, get a $12 ISP programmer instead so you can configure the chip's "fuse" options as well as upload code.
If you are only doing a one off project, have you considered just buying a teensy board? http://www.pjrc.com/teensy/
It is about as small as you can get and often for one offs, even the cost at $16
is very competitive to a DIY prototype using a perf/stripboard unless
you happen to have components laying around.
Back in #8, you asked about ICSP: those connect to +5, Gnd, Reset, and SCK, MISO, MOSI.
Can be a header as I did, or just connect temporarily to the needed pins.
There is no need for any external components, and no attiny/atmega dosen't even need a crystal. They (atleast all I've used) have an 8MHz internal crystal. All you need is voltage and ground.
Very nice. Don't you need to customize the boards.txt of the Arduino IDE for using the internal 8MHz ? I thought that meant using specific "fuse settings".
tochinet:
Very nice. Don't you need to customize the boards.txt of the Arduino IDE for using the internal 8MHz ? I thought that meant using specific "fuse settings".
I don't use the arduino IDE. But no, the attiny is not supported. If you want to use the IDE without any custom editing you could do the same board with an atmega168 and program it using "Arduino Pro or Pro Mini (3.3v, 8 MHz) w/ ATmega168".
io53:
There is no need for any external components, and no attiny/atmega dosen't even need a crystal. They (atleast all I've used) have an 8MHz internal crystal. All you need is voltage and ground.
Well, you really should have a bypass capacitor on VCC / GND and a pull-up on RESET.