I have a GPSDO that needs a 'real' (as in -ve and -ve voltages) RS232 and the Prolific cable that I bought causes all kinds of weird issues. I looked around but real RS232 adapters are not easy to find and many have flakey drivers or fake FTDI chips.
I also use the USB-Serial Geekcreit style PCBs a lot (see picture) but I bought a bunch from Banggood and they all had the same serial number! - I ended up buying FT232 ICs (which cost more than the original PCBs) and replacing the fake ones.
So I came up with this project idea, it's kinda a 3 in 1:
1. Stand-alone replacement for the Geekcreit style board
2. Optional MAX3227 RS232 voltage IC
3. Optional to have 5V isolation of the 5V supply to the MAX3227 with digital isolators in the TX/RX lines (not yet shown on attached schematic)
I'm thinking that 2 & 3 will be on a snappable PCB extension and the isolators will be optional on that PCB.
This design includes a feature to allow use with Arduino where the DTR pin allows an Arduino target to auto-reset when a new Sketch is downloaded.
I will bring all pins out to 0.1" headers, not sure if I'll include a DB9 connector, maybe I'll include as I already have the footprint but if not, I'll have a hi-voltage 0.1" header.
Attached is the very first cut (vn 1a) of the schematic for consideration, let me know if anyone has suggestions, request for changes, errors spotted, etc. I'm going to place a PCB order in about a week so please give me ideas & input ASAP.
[EDIT] I'm going to share this design with you guys for free use in case you were wondering. If anyone wants a PCB, let me know and can can order extra as needed.
Ted