Help!~ RF transmission from PIC to PIC

rf data transmission pic

Hi all,

I have a question regarding RF transmission from PIC to PIC. Please share with me your idea and thanks a lot for your help!!

Basically I am using USART of PIC16F877 to transmit data from one PIC to another. When I use wire to transfer, everything works fine. However, when I use RF transmitter and receiver just to replace the wire in between the two PICs, the receiver PIC receive garbage value and through to LCD.

Transmitter:RF RTFQ2
Receiver: RF RRFQ2

I do not use any decoder or encoder. I connect the TX pin of one PIC to the data-in pin of RTFQ2, and data-out pin of RRFQ2 to RX pin of another PIC.


This afternoon I used the system:
PIC1 - RF RTFQ2 - RF RRFQ2 - Oscilloscope
to check the data-out pin of RF RRFQ2 and found that the input signal from PIC1 and output signal from RF RRFQ2 almost have the same shape with (1). only a little lag (2). the output signal has a 4V voltage compared to 5V of input signal.

But when I connected the output signal from RF RRFQ2 to PIC2, the LCD gave junk value...
With wire the out put is: HAAAAHAAAAHAAAA...
With RF the output is: H****H****H****... * here represent junk code and its pattern is fixed, 4 fixed junk code followed by one H



Is there any special thing I should take care of for this kind of implementation?..
Attached is the test code of transmitter and receiver in C. If you want any other

information, please tell me and I'll follow up. Thanks in advance!

pic rf transmitter

anyone to help on this? I also have this kind of problem. If I use signal generator to be the signal source, what I receive are what I send. However, if I use PIC as the signal source, what I receive are totally different from what I send. I am sure it cannot be of the reason of noise... anyone to help?
PS: I just treat the RF modules as a wire directly connect to PIC pins.

rf pic

Hi,

Actually, before sending any data you have to send a sequence of 0 and 1 in order to get the transciever and receiver synchronized.
Also, You can think of implementing a datalink layer for the application so that the receiver can reject the erronous data checkd by a simple checksum calculation for exemple.

Cheers,
Advares.

rf pic data transmission

The only thing that comes to mind is that your data rate is too high.
I see in your code 9.6kbit, while, as far as I know, the RF modules are rated to up to 4.8kbit.
Try that instead.

Arthur

rf transmission

arthur0 said:

The only thing that comes to mind is that your data rate is too high.
I see in your code 9.6kbit, while, as far as I know, the RF modules are rated to up to 4.8kbit.
Try that instead.

Arthur

Click to expand...

9.6kbit is possible according to
https://www.planetonecomponents.com/part/FM-RTFQ2-433R.phtml

pic - rf transmission

Although it is rated at 9.6KBits/Sec. I suggest lowering the data rate.Because even the data rate may play a part. Also seems to me like you have some sort of a synchronizing problem as AdvaRes says as you are able to receive the output at times.So try lowering the data rate and see what happens.

rf transmission pic

Hi all, Thanks for your advice!! I'll first lower the baud rate to check the result, then I'll try to synchronize the sender and receiver.

AdvaRes, I am quite new in the field and not quite sure what is 'a datalink layer'. Could you elaborate it to me? Thanks!!

pic rf

boywsz said:

Hi all, Thanks for your advice!! I'll first lower the baud rate to check the result, then I'll try to synchronize the sender and receiver.

AdvaRes, I am quite new in the field and not quite sure what is 'a datalink layer'. Could you elaborate it to me? Thanks!!

Click to expand...

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

pictopic

Hi all!

I have lowered the baud rate and the result is almost perfect! Thank all you guys so much!!

Hi all am new to this forum and this is my first post,
I would like to know how to low the baud rate
I had a look at the datasheet
but couldnt find it
thnks for your help.

Which PIC are you using?

Keith.