Using Arduino Uno as a USB-TTL serial link to Casio FX-850P ?

[blackjetrock]

I don't think that will work as the TX and RX pins marked on the Arduino are the serial lines that go to the host PC. If you want to do this then you can use either a different hardware UART (on some Arduino boards there are multiple hardware UARTS) or a "software serial" library to create a second serial port on a pair of GPIO lines. If the data rate isn't too high you could also have code do the TX/RX functionality, if you aren't using the Arduino for any other tasks.

Arduino Serial info here:

https://www.arduino.cc/reference/en/lang...on/serial/

You also have to make sure that the Casio is Ok with 5V level signals and that it doesn't use 'proper' RS232 which requires positive and negative voltage levels.

Andrew