Why do you want to use a 32 kHz crystal? Running with the internal 128kHz watchdog oscillator (if necessary with CKDIV set appropriately) will give you most probably longer runtimes.
Well, say like that , yes ! I would like to use my mcu with a low consumption mode (50 uA @ 1.8 V DC). So 128 KHz i ternal oscillator may a valuable things. How to use the 128 KHz in a stanalone mode ? I have already used my atmel mcu (328 DIP) with a 5 V battery.
Step 0: Google around for avr fuses / tutorials and read the datasheet
Step 1: get hold of an ISP. I highly recommend the avrispmkii
Step 2: As soon as you have set the fuses to 128kHz WDT you will notice that you will not be able to connect to the controller anymore. This is because the ISP speed is to high. Thus lower the isp speed to 128/4 kHz = 32kHz. (BTW: not all ISPs support such slow speed, again a reason why I suggest the original). Do this BEFORE you change the fuses in order to be sure that your ISP will still be able to communicate with the controller.
Step 3:
Option a) use AVRSTUDIO to set the fuses accordingly
Option b) google for an avr fuse calculator, let it compute the fuses and use avrdude to set the fuses accordingly
Step 0 : I use http://www.engbedded.com/fusecalc/.
I have a large choice of 128 KHz with "6CK/14CK + 0ms" or "6CK/14CK + 4.1ms"... What doest i mean ?
Step 1 : I have already an abrduino uno. May it possible to use it as an ISP ?. Yes, I know that "Currently, you cannot use an Arduino Uno as an ISP programmer because the optiboot bootloader does not support this sketch. A revision for this is in progress. " according to http://arduino.cc/en/Tutorial/ArduinoISP.
With this combination you can attain a total current consumption well below 1mA. Cutting the track from the voltage regulator's output on the ProMini (also disabling the power LED) can save even more power.
Running at 3.3V saves the bother of running at a non-standard CPU frequency, which would cause problems with sketch uploads, serial communication, delay timing etc.
gege089:
Step 0 : I use http://www.engbedded.com/fusecalc/.
I have a large choice of 128 KHz with "6CK/14CK + 0ms" or "6CK/14CK + 4.1ms"... What doest i mean ?
The difference is only in startup delay. You should set it to +4ms or +64ms.
Step 1 : I have already an abrduino uno. May it possible to use it as an ISP ?. Yes, I know that "Currently, you cannot use an Arduino Uno as an ISP programmer because the optiboot bootloader does not support this sketch. A revision for this is in progress. " according to http://arduino.cc/en/Tutorial/ArduinoISP.