Maixduino & ESP32 intra communication


I am a newbaby with my maixduino K210. I plan to do image classification and want to send the estimated label to the ESP32 via UART. Many question :
i) What is the builtin pinout of the serial link between both chips ?
ii) Is there already a script doint such communication ?

To be honest, I am completly lost :slight_smile: Thanks in advance.