I share m5 support answer on the topic "UART0 is a specifically assigned for log print, it is encapsulated by ESP32 at lower layer. It will print the system log automatically and seems like we users are not permitted to shut it down, so we don’t recommend users to use UART0 as a normal UART series port, it will interrupt you communication. That why we connect it with CP2104." to me it's clear the usage of UART0 ..less cleare why this two GPIO are routed to the M5bus since can't be used I will use UART2 for my custom project with this assignment GPIO34=RX GPIO17=TX Davide

And the PCB files for ordering the board from JLCPCB. PCB layout of the MBUS referance.

@ajb2k3 Really thanks for your reply

@tokuhira said in PLUS Module problem about PORTB and PORTC: Please check your PLUS. [image: 1553865301365-swapped-ports.jpg] Thats wrong A0 and A1 are connected to the black port, Rx and TX are connected to the blue port.

@watson [image: 1552903271442-53808727_264318361185264_1820011547234140160_n-resized.jpg] Thank you sir, knife it work.

@ajb2k3, @watson Thank you so much. Uuum, stacking is very convenient but considering batteries is not convenient.

@dave-nardella Theoretically, it's OK.

Great, sorry you had to hack around to get all the modules to work together. We are working on improving the design to resolve these issues. What did you make? @tokuhira would love to see your project if you don't mind sharing.