Telnet and SSH are great to access a Linux device, machine and computer remotely when they are already running, but when you are working on the bootloader and/or kernel themselves, you’ll have to use a serial port to access the terminal / serial console. Boards used to get an RS232 port which you connected to your computer with a NULL modem cable, but these days, most boards and devices expose TTL signals and require a USB to TTL debug board to access the console via a USB cable. If you only have one device close to you computer that’s fine, but if your testbed is a little further. or you need to access the serial console on multiple boards you could consider using ESP8266 module to export the terminal over WiFi. This is exactly what Zoobab did above with a GL.inet router running OpenWRT and NodeMCU board with ESP-12(E) module […]
How to Use an ESP8266 Board as a WiFi to Serial Debug Board
