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Hello, I made the connection between the shield and the atmega2560 but I can't unlock the avr, it reads the fuses but doesn't write the ones I assign to them.
The connection between the shield and the atmega2560 was made through the image in the DataSheet of the atmega2560.

Please could you help me on how to write the fuses in the avr.

The 2560 uses the same HVPP scheme as the 328P and other parts. The signals and commands appear to be the same.

I haven't tested the 2560 myself but it should work.

Can you tell us the current values of the fuses and the fuses you are trying to set?

Can you also include a couple screenshot of your Arduino screen showing the communication with the shield and how you are entering the fuse bytes?

Note that not all fuses can be set, some are hardwired from the factory.

Make sure to triple-check your wiring, as HVPP needs all signals to be connected to work.

Which specific variant of the 2560 are you using? I see several variants listed at Digikey.

Conseguí unos fuses que trabajan con el cristal externo cuales serian los siguientes: LFUSE 0xB7; HFUSE 0x99; EFUSE 0xFF. Mediante el cableado realice bien la conexión guiándome de datasheet aunque leyendo en foros el bloqueo se puede solucionar mediante una muy baja frecuencia para poder reescribir los fuses aunque hay otra que no se podrá y se necesita el escudo, sobre la comunicación los fuses que muestra al leer son 0xFF 0xFF 0xFF, cual nunca le ingrese esos fuses y la variante es solo Atmega2560.
Saludos

Hello,

What is the part number of the ATMEGA2560 that you are trying to program? Can you please post a photo?

Thank you!