Hey everybody. I wonder if there is any way how to program standalone ATMega2560 with Arduino UNO R3. Or I can use USB interface as in Tic-Tac ISP? (link: http://www.instructables.com/id/Tic-Tac-USBtinyISP-Programmer/?ALLSTEPS) Thanks for soon reply!
Programming with the UNO as ISP programmer via ISP conector should work, only if the Atmega2560 is 5V compatible. Anyway, how did you do the Mega standalone? It is s surface -mount IC, isn't it?
I am creating that board right now. it is like Arduino 2560 clone, but it contains only that SMD chip, female pins and USB interface. That board I will make will go to instructables as Open Source (if it will even work). But also how to burn bootloader on it. Have I to burn it like on UNO or how?
Try Nick Gammon's Program Bootloader, and then connect an FTDI Basic to download sketches via PC USB Port.
See Page 47 of the datasheet as well:
10.7 Calibrated Internal RC Oscillator
By default, the Internal RC Oscillator provides an approximate 8MHz clock. Though voltage and
temperature dependent, this clock can be very accurately calibrated by the user. See Table 31-1
on page 371 and “Internal Oscillator Speed” on page 404 for more details. The device is shipped
with the CKDIV8 Fuse programmed. See “System Clock Prescaler” on page 49 for more details.
This clock may be selected as the system clock by programming the CKSEL Fuses as shown in
Table 10-9. If selected, it will operate with no external components. During reset, hardware loads
the pre-programmed calibration value into the OSCCAL Register and thereby automatically calibrates
the RC Oscillator. The accuracy of this calibration is shown as Factory calibration in
Table 31-1 on page 371.
If you are not using an exterlnal 16 MHz oscillator, then you will need to make fuse changes, boards.txt changes, and possibly even a new bootloader for the slower clock.
For reliable performance, you also need a 10K pullup resistor on Reset, and 0.1uF caps on all VCC/AVCC pins, and on Aref.
So I will get crystal right here, but I wonder if I have to use standard 16MHz or if I can use 27.145MHz crystal.
See 31.2.2 in the datasheet - 16MHz tops.
Thanks.