I downloaded this libraries and I was able to replicate your issue.
The error log says:
fatal error: ../SPI/SPI.h: No such file or directory
I did the following and I was able to compile/verify the code successfully
Go to the folder RS485 and open the file named RS485.cpp
Go to line#30 and change:
Let me know if you get better results with this.
It helps, no compilation error.
Now I have connection error.
I want to use function 03-ReadHoldingRegistaers according to Modbus RTU protocol.
There is a string " int result = node.readHoldingRegisters(address, bytesQty);" in one example,
but no parity bit and stop bit.
Could you post the example you are trying to run ?
How are you testing this? Are you using another instrument or do you only have the RS485 shield connected in the other side?
What do you mean with "but no parity bit and stop bit" ? Do you need these parameters to work with the shield?