how to connect this RFID connector to RS232 interface?

i have got a RFID mi-fare reader. i cant connect it to the computer .it has green (txt),white (rxd),yellow gnd. & red,black(power).can you show me how to connect this item to computer using rs232(com port)...it will be a great help to me..


thank you guys

You need a MAX232 chip to interface it with RS232..

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**broken link removed**

i made the circuit and i coundnt find the answer...whats the meaning of Vcc..i gave it 5v

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are the any solutions ????

https://en.wikipedia.org/wiki/IC_power_supply_pin

Vcc is the positive power supply pin, your connection is correct.

Alex

If not working, then do a loop back test to know if the MAX232 side is working..
For that, connect the Rx and Tx (max232) together and then type some thing on a hyperterminal or any terminal emulator and if you can see what you have typed on the received section, that side is okay... Also, try it without connecting the Rx and Tx and see the difference....

Now, you try connecting the RF module as in above figure.. Don't get confused that the Tx marked in above figure is the Tx of the MAX232. But it is the Tx of the other device, ie in your case , the RF module... Hope you understood....
Also, set the baud rate in PC same as that of the RF module... Hope you may be knowing how to opetate the RF module... If not, read the data sheet of your module...

Are we sure that the RS232 interface on the RFID module is TTL level? The module seems to have options for RS232 or RS485 (on different models) going from the sales literature I've found. I would have guessed that it means real RS232 levels, not 5V. I've not found a proper manual for the module so I don't know for sure.

If the module can be opened up, a photo might help determine that...

Are we sure that the RS232 interface on the RFID module is TTL level? The module seems to have options for RS232 or RS485.

Click to expand...

You're absolutely right. I really can't understand how people are guessing about TTL or RS-232 from a nothing but a signal name RxD and TxD. In this case, RS232 seems more likely.

I guess however, that the module is shipped with slightly more information...

FoxyRick said:

Are we sure that the RS232 interface on the RFID module is TTL level? The module seems to have options for RS232 or RS485 (on different models) going from the sales literature I've found. I would have guessed that it means real RS232 levels, not 5V. I've not found a proper manual for the module so I don't know for sure.

If the module can be opened up, a photo might help determine that...

Click to expand...

I don't understand where is this referring to, I didn't see any post in this thread that suggests a direct connection , there is only a schematic that shows the connection from the mcu to the 232 port using MAX232 and not directly.

Alex

FvM said:

I guess however, that the module is shipped with slightly more information...

Click to expand...

I would hope so; I wonder if the OP has it, and has read it...

alexan_e said:

I don't understand where is this referring to, I didn't see any post in this thread that suggests a direct connection , there is only a schematic that shows the connection from the mcu to the 232 port using MAX232 and not directly.

Click to expand...

What I'm trying to say is:

The OP hasn't provided any more information than a pinout labelled TXD, RXD and power.

Some people seem to assume that the module uses TTL-level RS232; I see no evidence to base this assumption on. If someone has actual experience with the module then that is different, but I'm not sure anyone so far has experience of it.

I've searched for literature on the module and can only find sales literature. This literature states that the module is available in RS232, RS485 and some other versions. Some of the photographs show it with a standard 9-pin D connector. Also, it is intended for remote placement from the controlling PC.

All of the above suggests to me that it does, in fact, use real RS232 levels, not TTL. Thus it simply requires a direct connection to the PC.

If it were mine, I would put an oscilloscope on the TXD line and see what the levels are, or open the module and look at the circuitry, before connecting it to the PC. Just to make sure I am correct. I imagine that the module could be damaged by the real RS232 levels if I am wrong, so I am wary of simply saying 'wire it directly' without further information.

Does that make sense?

OK, now I get it , the OP asked for a PC connection and the schematic was for an MCU connection.

If the schematic was intended as an interface between the device and PC and the mcu side is supposed to be connected to the RFID device while the RS232 to the PC then you are correct.

I just misread the schematic as a suggestion of how to connect an mcu to the RS232 of the RFID device.