C code for Manchester encoding and decoding a byte of data

[Munib]

manchester coding

Can some body give me C code to Manchester encode and decode a byte of data .
I am using PIC18F452 mcu and C18 compiler.

I need a function like

Encode(byte in)
{
return (byte [2] manchester);
}

Decode(byte [2] manchester)
{
return(byte out);
}

 

[rfmw]

mcu manchester coding

Thats really simple:

Encode your logic 1s as a 01 and your logic 0s as a 10 (or vice versa ... logic 1 = 10 and logic 0 = 01).

Example:

encoding a byte "11010001" results into MSB:"01011001" + LSB:"10101001"

simple enough?

 

[Munib]

manchester coding sample

Yes its really very simple to manchester encode and decode the data manually by ourself or by using a lookup table in a mcu
But what i want is some function to encode/decode the data in a mcu

 

[NoXuS]

mcu manchester decode

Maybe this website can be helpfull to you.

**broken link removed**

Note: I haven't used manchester coding myself but the implemetation looks fairly straightforward.

 

[Buriedcode]

Re: Manchester coding

Hi, just thought I'd add my $0.02

I've used manchester (similar to biphase) coding in a PIC16F818 to test the BER of an RF link. I did it by splitting my input byte into two 4-bit nibbles, and used a LUT of 16 entries (1 for every possible 4-bit combination). I think its only used a total of 10 lines of code, plus the LUT.

Pseudocode:
Move inbyte to temp register
Move to W
And with 00001111 ; gets rid of the four MSB's
Call look-up table
Move result to outbyte1
Swap nibbles in temp (swapf temp,W)
And with 00001111
Call look-up table
Move result to outbyte2

Note: outbyte2 is the 4-MSB, outbyte1 the 4-LSB.

And there it is, the LUT is simple as well: ie: 00000000 -> 10101010
with the last entry being: 00001111 -> 01010101
If you're unsure what to put in the LUT, theres plenty of info on the net about manchester encoding.

I think thats right, but I'm rusty. I did it ages ago, and maganged to get 1.5MB/s out of the PIC (with the aid of a shift register).

As for decoding, bit more tricky. A clever use of interupts could be used, since a '1' is an upward transistion, and a '0' a downward one. You'll need to add a preamble in your packet to train your decoder so it knows where to sample. (check for rising edge and transmit all 1's).

Hope this helps,

BuriedCode