https://github.com/LibreDMR/OpenGD77_Us ... a-to-radio
But I believe the buttons to press are P1 and Orange while one turns on the power supply to the radioTYT MD-9600 | Retevis RT-90
Hold the green power button and the orange button, while applying 12V power to the radio. Note updating the OpenGD77 firmware to a newer version does not require the power to be removed and reconnected
That is what worked for me.