I know from the documentation about Serial1 which is reserved for Bridge (MCU -- linux), also I found pins 0 and 1 are for Serial1.
But I think that sketch uploading is done by another way, is it possible? Why the bridge is using Serial1 if both sides can communicate with another way? Or what I missed?
Story behind this: In my project I started with RS485 library ModbusMaster then my next step was Bridge communication and I found I can't use Serial1 (pins 0, 1) for RS485 because Serial1 is for Bridge. But when I was blocking Serial1 by Modbus I was able to upload the sketch thru the linux (because I have some issue and I can't upload via USB) without problems.
So I'm going to move RS485 probably to SoftwareSerial. I can also resign Serial (debug) output and put RS485 to it but there is no pins bonded with Serial like as 0,1 with Serial1.