FT231X (BOB-13263 ROHS)

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Joined: Sun Oct 29, 2017 4:36 am

FT231X (BOB-13263 ROHS)

Post by MBEDS » Sun Oct 29, 2017 5:14 am

I have an ongoing need for real (old) RS232 signals (the ones that go positive and negative) for connection to a PC. I am thinking of a design that pairs an FTDI UART with a MAX3227E but I wanted to try to make it multi-purpose - i.e. it could run the real RS232 through the MAX3227E or it could run low-voltage RS232. This last requirement is the reason for the post, increasingly I want to connect a debugging UART to my development systems using 1.8 volt UART signals.

I see that the FT231X does all the RS232 signals and also claims that it can run down to 1.8V with VccIO set to 3.3V "with external pullup resistors". This seems to be lifted from FTDI's FT231X datasheet but nowhere does it say what the recommendations are for running that way and, if the FT231X was connected to an external circuit with VccIO set to 3.3 volts, wouldn't that mean that the external circuit would see +3.3 volts on the UART RXD pin or is the output setup as open drain?

I am pretty sure it's possible to achieve 1.8 volts by using an LDO regulator to reduce the FT231X's 3.3 volts out down to 1.8 volts and then feeding that back into VccIO. Questions:

1. What is the recommended way to get VccIO running at 1.8 volts on an FT231X?
2. Is the DTR causing RESET addition to the BOB-13263 just for the Arduino users' convenience or does it have some kind of standard application?

Any thoughts, guidance, advice, or shared experience on the above would be appreciated.

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