Connection with max232 hyperterminal and rf module

[luish]

Good morning.. I have a problem in a project I'm doing for college, I need to communicate two PCs via serial port using hyperterminal, max232 and rf module 433mhz. Tested only the serial connection between the two PCs with max232 and is working, the character that I type on a pc appears in the other. However, when using rf module the character I type on a pc does not arrive on the other, comes just a different character, for example, I type "t" and "T" appears (this was the closest I got to get ) or "r" appears and "@". Below is the components I'm using and the circuit. I could not find any datasheet with important information about the rf module. I need help on this, thanks.



Transmitter FS1000A (3V-12V)
Receiver XY-MK-5V
MAX232N (capacitors 1uf)

 

[betwixt]

They are rather poor quality AM (OOK) modules so don't expect good results. You probably find the receiver is picking up data even when the transimtter is unpowered.

Things to try:
1. drop the baud rate down, they are 'rated' to 9600 bauds but I suggest 2400 as maximum.
2. try inverting the transmitted and received signals, this will keep the transmitter running longer so interference at the receiver will be quietened. Wire the inverters at the TX module input pin and at the RX module output pin, not the PC side of the MAX232s.
3. check the modules work at the same frequency and you don't have one at 315MHz and the other at 433MHZ!

Brian.

 

[MUKESH.K.S]

What is the baud rate u r using? RF module does not reliably work with high baud rates
Reduce the baud rate to minimum and try again

 

[luish]

hi, I tried 9600,4800,2400,1200,300,110 (minimum) and realized that between 2400 and 1200 I have less interference, and the minimum I do not get anything. I also tried reversing the Tx and Rx cables and did not work. As the frequencies are also certain, 433 and 433MHz. I remember the tested modules with a function generator and an oscilloscope (pulse train) ... and receiver wave is coming with the width a little smaller, as shown in the figure below, this is right? I'll do some more tests here, for now thanks for the replies.

 

[betwixt]

I did not mean to reverse the TX and RX cables, I meant to invert the data on them. Try wiring an inverter (evan a simple single transistor will do) between the MAX232 and the transmitter and the same between the receiver and the other MAX232.

If that makes it more reliable there may be a software fix you can try but do the hardware trial first. The drawback to inverting is the transmitter is normally ON and goes off when data is being sent so the power consumption is a little higher but it will establish whether it is possible to kill the background interference the receiver is picking up by keeping the frequency occupied.

Brian.