Flashing a HP30b calculator through Arduino

Community General Discussion
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I am working on reprogramming a HP30b calculator to upgrade it to a WP34s, using my Arduino Nano Every with this tutorial. For one step, you pull the RESET pin to low on the Arduino, and then connect the RX and TX pins to the calculator's RS485 port. When I run the software on my computer it is supposed to write the bin file through the USB to the calculator, but the RX and TX lights do not light up, and the software cannot connect to the calculator.

Is there a direct connection between the RX and TX pins and the USB, or are they connected through the processor? If there is not a direct connection, then would the RX and TX pins still work if the Arduino is being reset? The tutorial was made with an old Arduino Nano, while I have a new Arduino nano every, so I don't know if they handle that in the same way.

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Through the processor. And you may need an RS-485 adapter for the TX & RX connections. A regular 5V data signal may work but it's normally a differential signal. There are special RS-485 transmitter/receiver chips.

It sounds risky... Are you going to feel bad if you brick your calculator.

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