Hi3516 Access Root Error

First, I apologize for my english. I have a camera module with hi3516 SoC and have to access to hi3516 as root. But I couldn't that.

If I begin to explain from start. I had an IPC, extracted it and now I have 3 modules (camera module, ir cut module and power / api module). I found 3 holes on camera module, these are GND, Rx and Tx. I soldered them with 3 female jumper cables and connect to ftdi module. I used micro USB to USB for ftdi-pc connection. Powered up camera module with 12V. In while, I download a program, what name is coolterm, to my pc. I opened coolterm and set baud rate to 115200 (hi3516 standard). Camera module booted up. I pressed a button when I see "Hit any key to stop autoboot: 1" text. Until here I followed an article and everything is fine. But that article says "You have to press enter after to type "root" to gain shell access" and I can't access shell when type "root". I got an error like "Unknown command 'root' - try 'help'". Hi3516 has embedded linux os.

Article Link: https://felipe.astroza.cl/hacking-hi3518-based-ip-camera/

Any ideas to help me?