PIC-PIC RF Comms

[rhino]

If you look at what im sending you will notice that it already in machester format:

$55,$55,$66,$95 = 01010101 01010101 01100110 10010101

Not sure I agree with this statement. I'm no RF engineer by any means, but I think the manchester equivelent for this would be:

0110011001100110 0110011001100110 0110100101101001 1001011001100110

Melanie explains it HERE very well.

[Kamikaze47]

What im saything there is it is allready encoded. If you encode 1111 1111 1010 0111, you get 01010101 01010101 01100110 10010101 which is what im transmitting. The numbers you worked out is what you get if you encode 1111 1111 1010 0111 twice

[rhino]

OK... gotcha.... what, you don't want superdooper redundant encoding? Just kidding.

[languer]

You want to try and figure out if SERIN2 is hanging on the wait qualifier or if it is receiving garbage after the qualifier. You could try something like this:

start1:
Serin2 PORTB.1,16572,[qual]     ' wait for $66, then store data
if qual=$66 then start2
goto start1

start2:
Serin2 PORTB.1,16572,[recvd]     ' once qualifier is recieved store data new data
if recvd=$95 then High PORTB.0              ' if recvd=1 turn on LED
if recvd=$99 then Low PORTB.0               ' if recvd=2 turn off LED
goto start1                                  ' loop

This will not hang the SERIN2 command on waiting for $66, it's kind of crude and it will not be great if it misses sync (i.e. receives $95 before 66$). To properly do this you want to have what is referred to as a ring buffer (good topic for search).

[Kamikaze47]

Ive tried adding the "DEFINE CHAR_PACING 1000" line, but it dosnt seem to have made much difference either.

The range is still about 15m with obsticles, or 30m line of sight... That might be as good as it gets?

[Ioannis]

These modules you are using should get further but long time ago, I run a test on these and was disappointed by their behaviour. Then switch to Aurels and after that I am building my own modules for superegenarative and hyperodyne ones.

I would suggest if you don't need many, to try some other brand.

Ioannis

[mikem]

I'm using the same receiver transmitter combo and I reliably obtain 200 feet indoors and over 300 outdoors running the transmitter at 5 volts using 1/4 wave antennas at each end.

Here is what I found; in 2 installations that I did I found that the receiver needed to be tuned to the particular transmitter.

As a result I wrote a short program to continuously send a simple serial signal consisting of a pre-amble character, the letter H for example, and a data value such as a string of 01010101.

I sent these basic commands only to Keep things simple at first when tuning the receiver.

I then moved the receiver board away from the transmitter until the signal level as indicated by a flashing LED on the receiver board went away. Next I slowy adjusted the tuning coil on the receiver board until the LED came back on. This is a very very sensitive adjustment so do not move the tuning slug more than 1/2 turn in either direction.

I repeated this each time increasing the distance between the transmitter board and the receiver board until the LED went out. I found the tuning to be very very sensitive, even a 1/8 turn of the tuning slug resulted in a loss of the demodulated signal.

Next I took 2 untuned receivers to work and measured their input impedance on my HP network analyzer and I found a very narrow match on each one.

Both of the unalaigned receivers as they came from the factory were either tuned below 432.85MHz or above 434.5 Mhz. between 433.2 to 434 .25 Mhz they had a match of over 2.5 :1 VSWR which is a poor match for these modules.

I compared these to the 2 that were tuned using the method above and the 2 tuned receivers were showing a near 50 + J0 match at 433.75 and 433 .95 Mhz respectively.

When I get some more playing time I plan on running some further test using My HP spectrum analyzer to try and determine, dB wise, how sensitive the receivers tuning adjustment actually is.

Mike