I have already tested the MAX485 chip directly connected to the micro controller on a prototype, and everything worked. For my needs I made another card (pcb) with two chips (MAX485 and MAX3232) so I have 0 uart for two devices, I had to add the SC16IS752 chip to switch from I2C to two UARTs.
I carried out several tests and I noticed that the problem would come from the chip and the library. When I use READ register function I read nothing at all, then I use WRITE function and notice that it writes fine to a register, but when I read again I read another register and it tells me that it’s empty !
When I use the ping function, it just writes to a register and reads that same register and everything works.
So the problem would come from writing and reading, the registers read and write sound different I get the impression. But since this library is supposed to work I wonder why I have this problem …