It could be a voltage level issue as RS232 specification was originally 12V and the Philips RFX is only 5 V.
The fact that the Arduino is having issues as well points me in this direction.
You might try a voltage level shifter. (search amazon) between the 2 ports and use +12V as a reference. You could also try using a MAX232 (again search amazon) and use +12V as input to that board.
I found this. Maybe it will help?[Link: forum.allaboutcircuits.com]
Last edited by Lyndel McGee on December 12, 2020 17:37.