Hi Geethu,
“I am doing a project on RFID based shopping cart…but now am having a few problems. I am having trouble connecting RFID module to the microcontroller(AT89S52) am using.
The RFID module i purchased consists of EM-18 reader module and it has been connected to max232 and then to RS-232…so the module has rs232 output..now can i connect directly from rs232 to tx pin of microcontroller? or is there another way?”
No you can’t connect the module directly. You must use another MAX232 between the module and the MCU
“Also, I have a transmitter for which am using MO-SAWR-ASK transmitter. That is to be connected to my microntroller (AT89S51). Is it ok to connect its data pin directly to the Tx pin of uc?”
Go through the datasheet of the transmitter and find out what is the maximum data rate at which it can operate. If you are directly connecting to the Tx pin of MCU, make sure that the baud rate which you have coded for the serial communication is less than the maximum data rate of the device
I think baud rate of 1200 will work with common transmitter modules
“And the receiver OX-RX02-ASK recieves the data and this is to be connected to a second microntroller. Can i directly connect its data pin to Rx pin?”
The baud rate setting should be considered here as well
“I also have to recieve the same to a PC or laptop. Now a days laptops dont have RS232 port, so how to receive the same in pc?”
Connect to the USB port of your laptop using serial-usb converter. Available in all electronic shops.
“can i use a 3rd uc, so that receiver is connected to uc, then to max232 then rs232, but then how to connect from rs232 to pc/laptop?”
If you use a serial-usb conveter then no need of a third MCU. Always try to keep the hardware as simple and compact as possible.