Hi, I have Arduino and PC. Arduino sending data over RS-485 to PC (only 2 device). PC to Arduino do not send any data - I have one direction communication.
PC is TL-WR741ND v4.x WiFi router. In OpenWrt wiki is:
Output level is 2.5V with good flanks (measured with digital oscilloscope). Input is via a 1k/3k voltage divider, which does not make the RX line 5V tolerant! Connection needs a 3.3V RS232 level shifter, or can be directly done with, e.g., the Bus Pirate. Pins on the connector in the photo are from the left TX-RX-GND-3V3, as expected.
I measured RS-232 (UART) output from MAX485 using voltemetter on PC side and incomming data has about 5V.
How can I reduce 5V output to 3.3V only in one direction. Can I use resistor? Or must I have complicated part as MAX232 (some version for 3.3V)?
Thank you for your help!