There is properly working kit
- USB<>RS-485 adapter (CP2102+ADM3485ARZ, terminated by Rt=120 Ohm),
- short cable
- PCB (ADM3485ARZ (also Rt=120 Ohm) +ATmega8A under +3.3V PWR)
I need to increase the PCB power supply for ATmega8 up to +5V,
but to leave the same adapter with ADM3485ARZ in complect and
WITHOUT ANY CHANGES IN THE SOFTWARE.
After replacing <ADM3485ARZ+ATmega8A, U=+3V3> by <ADM485ARZ+ATmega8A, U=+5V>
the failures appear in data exchanges.
If my problem may be solved by placing pair of resistors (AN-960.pdf, page 6 'Open Fail-Safe'),
how one should calculate R1 & R2
-two PCBs under +5V PWR (ADM485ARZ),
-three PCBs under +3.3V PWR (ADM3485ARZ),
are connected to cable?
And are there AD ICs for 3.3V and for 5V, which may be connected to one cable without additional pull-up, pull-down resistors?