1/3-2/3 pulse decoding library for PIC ?

hi
does somebody have 'drag and drop' asm library for decoding 1/3-2/3 pulses ?
bit 0 is 1/3 x total period logic level 0 and 2/3 x total period 1
bit 1 is 2/3 0 and 1/3 1
this code can be inverted, no matter
thx

Hi tgq,

Seems like you are trying to decode Manchester Code. Don´t know about 1/3-2/3 pulse decoding, pls drop a line about your application.

humber555

tgq: I'm using a simple code what is nothing else then a seriell bit shifter.
In my application I get a coded data stream with 13bits. I trigger on the first edge this give me the sync, the frequency is known so I only have to poll the input pin every bit period.
Some things to keep in mind:

1. Sample in the middle of the bit, maybe the reference isn't stable so the bit timing is changing a few percent.

2. The above use method only works in clean enviroment, if you have a lot of noise use oversampling. In some RF applications I also do a bit measuring to get timeout's (if the bit is to long).

3. A other way to survive in noise enviroments, use a ADC and othersample the signal. With some small filters you can get good results.

Regards

PS: Take a look at the microchip application notes for decoding a Keeloq encoder with a pic.

Hi Humber
its not a manchester code but a keeloq or MM53200-like code (see picture)

Hi MrProgrammer
yes at this point i've made start bit measure/discriminator, code bit decoder with resynch, time-out and 3 samples/bit (3 samples/bit found in keeloq appnotes :lol: )
but i have to make recynch pulse detector (not easy if jitter), improve bit noise immunity with oversampling, adjust bit pulse length vs start bit length (i may have +/- 50% shift between 2 RC oscillators) etc