Hello, I'm new here.
I'm trying to connect a rfid reader device to my Arduino mega. It has a USB connector which works when connected directly to the USB on the computer. However, I want the RFID reader to interact with my Arduino, and plan to use the RS 232 pins to do so.
The reader has RS 232 TXD and RXD. Question is, can i connect the RS 232 TXD RXD to Arduino's TX RX pins?
Thank you in advance!
I'm trying to connect a rfid reader device to my Arduino mega.
Which one?
The reader has RS 232 TXD and RXD. Question is, can i connect the RS 232 TXD RXD to Arduino's TX RX pins?
Not directly. If they really are RS232 levels, the voltage is wrong and inverted.
It will be far simpler to get an RFID reader that can be directly connected to the Arduino. SeeedStudio and Sparkfun both have them.
Yes,
you will need an RS232 shield that is compatible with your mega.
Thanks for the replies!
I got to use this particular RFID reader because its UHF, i can read far distances like >30cm, while those on Sparkfun are mostly 125kHz readers and only good for a couple cm. It's a aliexpress-bought RFID reader (http://www.aliexpress.com/item/usb-to-uart-rfid-uhf-reader-module-ISO18000-6C/32411250075.html?spm=2114.031010208.8.35.yA7Jm1 <- am i allowed to post urls?)
Can a RS 232 shield work? I'm really hoping to make this RFID compatible with my arduino because its quite expensive 
If the RFID module is genuinely RS232 it should work with the shield.
But a lot of people confuse RS232 with async serial from a UART, even those who should know better like people selling hardware gadgets.
So you need to find out if it is actually using RS232 voltages (+-12v), or is it really just serial at 0-5v.
A link to a manufacturer's site is far more useful than a link to a site that can do no more than take a picture of something that they haven't a clue about.
Power up the reader from a pc and measure the voltages on the rs232 pins using a multimeter. I would guess the voltages are 5v instead of 12v since it is normally USB powered. You can make a simple rs232 to TTL inverter using a transistor and two resistors.
Wow, thanks a lot guys! Will keep you updated