USB to TTL isolated interface

[HighTechPower]

Hi. I'm using FT232RL and Si8621 as isolated interface USB to microcontroller UART in my upcoming programmable dc electronic load project. Plz attached here find the schematic. While ordering Si8621 in SOIC-8 package I have found it comes in two varieties of default output state. One is active low while other is active high as below,
Si8621BC-B-IS (active low default output state)
Si8621EC-B-IS (active high default output state)
Which one I need for pic microcontrollers interface (PIC16F877A & PIC16F690)
Also correct me if there is something wrong with the schematic before going to PCB layout.
Plz attached here find Si8621 datasheet as well.

 

[KlausST]

Hi,

UART signals usually are idle high.

Klaus

 

[danadakk]

RS232 Standard and RS485 high (as Klaus said) -

RS232 Specifications and standard - Lammert Bies

Practical discussion of the RS232 standard and its specifications and properties.

www.lammertbies.nl

https://www.ti.com/lit/an/slyt324/slyt324.pdf

Regards, Dana.