HOW can I program arduino with WaveShare RS232 ??


I have
can I use it with Arduino UNO or Leonardo**?**
I have VERY OLD laptop with only RS232, LPT ports and NO USB

This seem suitable to me. You can connect it directly to the ATmega on the UNO bypassing the USB hardware that is on board.
I don't know about the Leonardo because it has USB capability built-in and not as a separate chip like the UNO

but HOW to connect it**?**

VCC -> 5V
TX -> RX
RX -> TX
RTS -> Reset
CTS -> ?

Look here on how to connect an FTDI cable. you need a capacitor in the RTS line. I am not sure about RX and TX on your serial board: RX is marked with an outgoing arrow, so it may be the transmit (TX) pin. To protect the chips just insert an 1k resistor in the RX and TX lines. If it does not work exchange RX and TX

I don’t understand why to use 1k resistor between RX and TX and if that does not work to switch…

anyway… I connect VCC and GND to UNO and nothing appears

any ideas**?**