My previous post (Pictures from the previous post as well)
So far all of the answers and comments yielded no solution to my problem.
This post offers a different method to communicate serially with the reader.
I bought a serial to USB connector cable.
I connected this to my reader and then to my PC's USB port. I opened the Arduino serial monitor and behold my amazement I was reading data correctly. So I thought why couldn't I strip the USB connector and expose the Vcc, GND, TX and RX wires. So I did.
I then connected the Vcc to +5V (Arduino), GND to GND (Arduino), RX to TX and TX to RX. I then opened up the serial monitor after uploading the serial code but still no data. I then changed the RX to RX and TX to TX and still no data.
However, when I connected the serial to USB cable straight to my PC (before striping the USB connector) the serial data was been correctly transmitted and viewed from the serial monitor. So why when I put my Arduino as the "middle man" the data does not go to my PC serial monitor?
The baud rate was 115200. I cannot change this baud rate because it is the spec of the reader. Additionally, I transmitted data successfully at 115200 by using my PC as the host (using Putty at 115200). So the baud rate is not the issue.
Best Answer
I suspect that much of the trouble you're having is from trying things haphazardly and/or not communicating very well here what you've tried and/or not understanding or following suggestions made here and in your previous question.
You have established that your RFID reader is communicating over its serial port by connecting it to your PC using the USB-to-RS232 adapter cable. This is a good start.
Do you have access to another USB-to-RS232 adapter which you haven't unfortunately mutilated (or are you confident that you could to a really good job repairing the one you cut the end off)?
It would be good if you could similarly establish that your Arduino can talk to your PC through the RS232-TTL adapter and USB-RS232 cable - and this step may also require a "null-modem" cable/adapter to swap the TX & RX pins on the RS232 side of the connection between the 2 adapters (NOT on the Arduino/TTL side).
For clarity - the "Gender Changer" adapter you show in the pics is almost certainly not a "null-modem".
You may have to try swapping the TX and RX lines between the adapter and your Arduino, as well as using or not-using a "null-modem" adapter between the TTL adapter and the USB adapter.
Note that there a 4 different configurations here which you may need to try! If you see this working - do not change the Arduino to TTL adapter connections again as this is now the only correct configuration.
If you're not able to complete the above step due to lack of suitable hardware it's not the end of the world, but there's less certainty going forward that you don't have some other issue on the Arduino end of things.
So now you're at the stage where (hopefully) you know that your Arduino can talk through the RS232-TTL adapter. The only piece of uncertainty left it whether or not you need a "null-modem" between that and your RFID reader to swap the RS232 TX & RX lines. There are only 2 options here - either with the "null-modem" or without it. One of those should work. If you weren't able to verify your Arduino comms earlier, then there's also the possibility that you need to swap the Arduino-TTL adapter TX & RX lines - another 2 options. So there are again 4 possible configurations - make sure you try them all!