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Topic: Not all 100 pins of ATMega 2560 are used in arduino mega (Read 262 times) previous topic - next topic


hello everyone i recently saw that there are 16 pins still left in the atmega 2560 ic which has no connection to arduino board ,is there some way that i can utilize that 16 I/O pins in my project.
the unused pin no of ATMEGA 2560 which is 100 pin ic are:
1)pin no 4(PE2)
2)pin no 8(PE6)
3)pin no 9(PE7)
4)pin no 14(PH2)
5)pin no 27(PG2)
6)pin no 28(PG3)
7)pin no 29(PG4)
8)pin no 47(PD4)
9)pin no 48(PD5)
10)pin no 49(PD6)
11)pin no 65(PJ2)
12)pin no 66(PJ3)
13)pin no 67(PJ4)
14)pin no 68(PJ5)
15)pin no 69(PJ6)
16)pin no 79(PJ7)


You'd need to do some precision soldering with magnet wire to connect to those pins.

If you do that, you can use MegaCore's "AVR pinout" to use all the pins on the ATmega2560 with standard Arduino I/O functions:


can you tell in detail what exactly should i do.
step by step


Please explain exactly which process you want me to give you steps for.


i have been using 7"tft and various other library so in total i only get 37 i/o pins on arduino mega 2560 so i saw the schematic of it i saw that 16 pins are unused which are general purpose i/o only.
and all of them are listed above.i want to use all the 16 pins (total 37+ 16 =53)so what all should be done
like sholdering or adding diffrent library or modyfing please tell me about it


The first thing you need to understand is those pins on the ATmega2560 are not connected to anything on the Arduino Mega PCB. In order to use any of those pins you will need to get some hair thin magnet wire and super carefully solder that wire onto the tiny pins on the ATmega2560 microcontroller chip on the Arduino Mega board while making sure that the solder and uninsulated parts of the wires don't make contact with the other pins. This is possible but it requires a lot of soldering skill.

This video will give you some idea of what is involved:
In a way, they have it easier because they are working on perfboard while you're going to just have a bunch of thin wires hanging in the air, only connected to the MCU via fragile solder joints.

It's certainly doable but in the end you might be better off just starting from either a custom board or else a TQFP-100 breakout board. They sell universal TQFP breakouts like this:

Of course soldering a TQFP is a bit tricky also but I'd say a bit less than the magnet wire, especially with a little practice.

So you need to determine whether that's something you want to jump into and then make sure you have all the necessary equipment and supplies.

As far as the software side of things goes, there are excellent instructions on the MegaCore page I linked above. If you end up with any specific questions after looking at them then let me know.


You could also use something like the Mega2560-CORE by Inhaos datasheet,
that has a lot more pins broken out. I'm not shure if they left some out, check yourself.

The have a nice protype board for that modul also (with 4.096V precision voltage reference).

Ah, this is obviously some strange usage of the word 'safe' that I wasn't previously aware of. (D.Adams)

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