Hi, I want to use my HC-05 Bluetooth module as a HID device. I downloaded the modified firmware for the HC-05 and now I want to flash it.The problemi is that I don't have an ISP programmer and the FTDI module that I have hasn't got the right pins. Can I use my Arduino to program the HC-05? Here is the guide I used https://mitxela.com/projects/bluetooth_hid_gamepad
If certain conditions are met, technically speaking you could:
It would require an older Arduino board with an FTDI-chip and no other USB/Serial chip variants (the project you are refering to exploits a special mode only the FTDI-chip supports)
RX and TX are easy, but you need to connect some of the handshake-pins from the FTDI to your module. This means soldering tiny magnet wire to some of the pins on the chip. If this is unknown territory for you, stop here and purchase a seperate board with an FTDI-chip on, instead of possibly destroying your Arduino.