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

[Liam Hays]

(07-20-2022 04:19 PM)Dan C Wrote:  As i have an Arduino Uno board, i was thinking of using it as an USB-TTL serial link to my FX-850P
to transfer programs and memo data between my PC and the FX-850P.
And then use a standard terminal program like Putty on the PC to transfer the stuff.

I was thinking wiring it up like this:


What do you think? Is it a possible way to do it?

Yes, it is possible. Upload an empty sketch to the Arduino (see below), and use the hardware TX and RX pins on the Arduino header. The empty sketch is to keep the ATmega chip from trying to also use the serial lines, freeing them up for your use.

As blackjetrock said, you should also verify the voltage level on the calculator. For example, my Casio fx-9750G PLUS uses 3.3V logic levels. Arduino Uno and most ATmega-based boards are 5V logic. The fx-850P port you pictured reminds me a lot of RS232, so you may need a MAX3232 or other RS232 converter.

Empty sketch (just to keep the ATmega busy):

Code:

void setup() {}
void loop() {}

What file transfer protocol does the 850P use? XModem?