Hi, I'm just thinking of this. Many arduinos come with two processors, one 16u2/8u2 and one main processor, be it 1280, 2560 or 328. It has been said that 16u2 is there as a USB serial adaptor to assist downloading of sketch into the 328, but I discovered that it is still using the bootloader-stk500…

Boards with 16u2 - Uploading sketch directly on ISP (from USB) - #6 by system - Suggestions for the Arduino Project

Topic		Replies	Views	Activity
Can we use the 16U2 on arduino as a ISP ? For itself and for other boards also. 3rd Party Boards	11	2814	May 6, 2021
using the onboaurd 8/16u2 as isp? 3rd Party Boards	16	4725	May 6, 2021
Additional function for Atmega 16u2 that could replace bootloader Suggestions for the Arduino Project	2	770	May 6, 2021
ATmega8U2 Bugs & Suggestions	8	8391	May 6, 2021
Arduino Uno/Mega R4: Program with ICSP. Suggestions for the Arduino Project	3	4181	May 6, 2021