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[kwe]

Hi

I would like to build a USB <-> RS485 device based on FT4232H.
In the documentation I found such a sentence: "Adding an external EEPROM allows selecting the TXDEN for RS485 mode when asynchronous serial
interface has been selected. "
Is it necessary to add an external EEPROM to allow communication via RS485?
Is it possible to configure this at every startup without using EEPROM?

Regards
Krzysztof

[FTDI Community]

Hi,

Yes, you require an EEPROM to communicate in RS485 mode because, as you have discovered, adding an external EEPROM allows selecting the TXDEN for RS485 mode.

When used without an external EEPROM the FT4232H defaults to a quad USB to an asynchronous serial port device. If no EEPROM is connected (or the EEPROM is blank), the FT4232H will default to serial ports.

Adding an external EEPROM allows customization of USB VID, PID, Serial Number, Product Description Strings and Power Descriptor value of the FT4232H. Other parameters controlled by the EEPROM include Remote Wake Up, Soft Pull Down on Power-Off and I/O pin drive strength. Note that the EEPROM contents have no effect on the selected mode with the exception of selecting the TXDEN for RS485 mode when asynchronous serial interface has been selected in software.

I hope this helps.

Regards,
FTDI Community

[kwe]

Thank you