I have my old and fully bricked Ti-Nspire CX (no CAS) and an old Raspberry Pi 3b. Is it possible to flash a boot2 file with my Raspberry Pi? The pins have a voltage of 3.3V and I think the Nspire does need 3.3V, right? If I am right I must connect Rx, Tx and one gnd of my calculator to my Pi and then I should be able to flash a boot2. But what is the best way to connect them?
Sorry, but I don´t think it would work. To restore your calculator, the normal proccedure needs a program called "HyperTerminal", which is an acient WIndows program and the Raspberry Pi can´t run Windows from what I know. But even if it works in someway with some linux alternative, I wouldn´t choose this route. But I don´t have a raspberry pi and never used one so, maybe I´m completly wrong of course.
I have plugs which exactly fit on the pins of my Pi but what can I do to connect the Nspire? I don't want to solder wires on my calculator...
You don´t need to solder anything and you shouldn´t,except the pins in the USB-TTL adapter, which is the only way. Generally you just need to manage to get the plastic part that is on top of the pins. I used some tapes to make the plastic piece stuck a bit behind, lifted it a little bit and got the plastic part to stuck the cables behind. I should point that you only need to connect one GND, and from my experience, connect the one that is away from the others. If the output in the terminal is strange symbols or boot2 fails to send, try to mess a bit with your TXD and RX cables