RF and Manchester

[Bruce]

Here's a simple set of manchester encode/decode routines.

inbyte	VAR	BYTE
outword	VAR	WORD
inword	VAR	WORD
outbyte	VAR	BYTE
i	VAR	BYTE

Begin:
    CLEAR
    inbyte = 12	       ' byte for test
    GoSub Encode       ' convert to Manchester word
    inword = outword
    GoSub Decode       ' convert from Manchester word
    outbyte = 0
    goto begin
    
Encode:
	For i = 0 to 7 ' loop for 8-bits
	  outword.0[(i*2)] = ~inbyte.0[i] ' Get bit value for bits 0,2,4,6,8,10,14 in outword
	  outword.0[(i*2)+1] = inbyte.0[i]' Get bit value for bits 1,3,5,7,9,11,13,15 in outword
  	Next i  ' 
Return

Decode::
	For i = 0 to 7			' loop for 8-bits
	  outbyte.0[i] = ~inword.0[i<<1]	' outbyte bits 0-7 = inword bits 0,2,4,6,8,10,14
	Next i  ' Inverts each 2nd bit position in inword I.E. 01 = 0, 10 = 1
Return

[Pesticida]

HI,
Bruce thank you verymuch,now I can good sleep :-).
I must now this test !
Now I understand how word modifier are working.
Thank you .
Thank you.

Regard Pesti.

[Pesticida]

Hi,
I have another question Bruce how can I compare 2 or more bytes when I just a example receive from transmitter byte0 = 241 byte1= 246 on the decoder output?
Can I do that like this:
if (outbyte = $F1) & (outbyte = $F6) then hserout [outbyte]

Thanks.
regard Pesti.

[Bruce]

Hi Pesti,

Your example should work fine.

[Pesticida]

Hi Bruce,
I have analysed the data from my transmitter I become this when i push the button:
24124625025424224224824225424124625025424224224824 2254

But when I dont push the button ,the receiver send to PIC this"I think this is just noise or Alien data :-)" :
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romHERE2412462502542 42242248242254241246250254242242248242254ToHere"24 224224324124024.............

I must to filter the data what I need :2412462502542422422482422542412462502542422422482 42254
I try this: if (outbyte = $F1) & (outbyte = $F6) then hserout [outbyte] but dont work !


How can I do this Bruce, simple as possible :-)

Thanks.
Regard Pesti

[Bruce]

A few things to consider.

1. If you do not clear a variable it will retain the last value placed in it.
2. Most inexpensive or sensitive RF receivers will output random noise spikes when the transmitter is idle.

Try sending data in packets of a specific size, and using some form of synchronization byte at the start of each packet. Receive your data in a specific number of bytes. If the first byte is not the synch value or character, dump the data packet.

It's rare that you'll see a solid RF application just flinging random data at a receiver.

[Pesticida]

Hi,
Did some one know how can I separate from a word bytes,Example :
I receive with serin 10 bytes,how can i show this bytes with serout.

Regard Pesti.