Serial Monitor 3V3 ttl to RS232

thingiverse

openscad sources included. Rename file rs232-hwhs.pdf-data to rs232-hwhs.pdf for a full resolution schematic. This project is a small box that sits inline in a TTL to RS232 cable. The project monitor 4 signals in the cable and displays the signals on a series of LEDs. The signals monitored include the RX and TX lines as well as the hardware handshake lines RTS and CTS. The DSR/DTR/DCD lines are shorted together allow the PC end of the line to be detected and to show as online in your serial communication package. One item to note: the small board shown in project came from china and contained a defective MAX3232 chip (bad Chinese clone??). It worked on the RX and TX lines, but when I tried to use the 2 spare channels for RTS/CTS conversions... setting the CTS line high caused the TX data to levels to crowbar to 1V (invalid). The system did not recover until the PC end of the cable was unplugged. I ended up rebuilding the convertor electronics using a real MAXIM 3232 chip on a small piece of perf board. There have been numerous complaints online about fake max3232 chips and I think I found one!.