The ARDUINO is a hardware platform based on AVR processors. ARDUINO boards/chips are programmed with a bootloader. This bootloader is the old STK500 protocol, not longer supported by Atmel in Studio. There are various programmers for ARDUINO, AVRDUDE is probably the most versatile.

 

BASCOM also supports the ARDUINO/STK500 v1 protocol. the DTR/RTS lines are used to reset the board.

You can program/read flash/EEPROM but you can not read/write fuse/lock bytes. The STK500 bootloader for ARDUINO does not support this.

 

Under options you only need to select the programmer, and the COM port. Since an FTDI chip is used on most ARDUINO boards, this is a virtual COM port. Only present when the USB cable is connected to your PC.

Select 57600 baud for the baud rate. Older ARDUINO boards work with 19200 baud.

 

ARDUINO V2

The developers of the ARDUINO finally implemented the STK500V2 protocol. This protocol is supported by Atmel and of course by BASCOM.

Select the ARDUINO STK500V2 programmer in BASCOM programmer options to use this protocol.

A board like the MEGA2560 R3 uses this protocol and probably all newer AVR based ARDUINO boards will support this protocol. The baud rate should be 115200 but could be different for your board.