Okay, here it is. My board can be found here, the uxcell DB9 RS232 Serial Female Port to TTL Converter Module Adapter DC 3.3-5V: https://www.amazon.com/Serial-Female-Converter-Module-Adapter/dp/B00R1LYEPS/ref=sr_1_8?ie=UTF8&qid=1500563647&sr=8-8&keywords=uxcell+RS232+to+ttl
The sensor is the AliCAT Whisper, manual here
And here is the wiring diagram of what I tried. This set up, when attached to a usb-rs232 converter, will give the correct output on putty. However, I see no response from my photon. If I switch the wires labeled “RS232 Input” and “RS232 Output” I still see nothing on my Photon and I also get no results when I attach a usb-rs232 converter
The only times it has worked is when I accidentally touched the lines of the “RS232 Input” and “RS232 Output” like this:
Let me know if that is more clear. Thank you for your interest