Serout/serin issues, advice required

[skimask]

2 PICs, both running on the internal clock, TX'ing and RX'ing 2400 baud serial...
Almost sounds like a recipe for 'no worky' to me.
Any way you can modify the circuit to plug in a crystal or resonator and try it out that way?

[Agent36]

Hi Skimask,
I had the simple data tx/rx working ok over wireless on the internal clock, I could try it on crystals (once I order some). Does the code look ok apart from that? Have not used serin/out much.
regards Nick

[skimask]

I'll take a better look at the code later on...(heading out the door)...
I think the fact that it was working and now it's not working is just luck. Internal freq varies with temp, voltage, humidity, sun spot cycle, color of pants, you name it, it varies because of it...ok maybe not everything
Moral of the story, usually internal osc's are hit/miss when using serial.

[Bruce]

SerOut txout, n2400, [ $aa,Manch ] is only sending $aa followed by the low byte of Manch.

SerOut txout, n2400, [ $aa,Manch.LowByte,Manch.HighByte] will send both bytes of Manch.

Modify the receive routine also. SerIn rxin, n2400, [$aa], Manch.LowByte,Manch.HighByte.

[Agent36]

Hi Bruce,
Thanks for that, was not 100% sure if I could send a word out in a single statement, just looked at the serout command in the manual and found the answer on the 2nd line.
I will modify the code later tonight and see what happens.
regards Nick

If anyone uses the code I have posted you need to change-- Manch var byte--to--Manch var word---in the Tx code. This have me stumped for 10 mins..lol.

[Agent36]

Hi Skimask and Bruce,
Thanks for the info, I now have my project up and running. The only other changes I had to make apart from the ones already listed, was to change the variables used in the ADC result and PWM output.
regards Nick

[BrianT]

If your system loses or gains half a bit time due to noise, clock slip, whatever, then Manchester goes out of sync and stays out for the rest of the message. BiPhase on the other hand is brought back into sync with the arrival of the very next '1' bit. BiPhase does not propagate errors. The code for biphase is virtually identical to manchester. Manchester needs very high accuracy clocks at both ends. BiPhase is much more tolerant of clock differences. The downside of biphase is that the channel needs a somewhat wider bandwidth.

Search for biphase code in the forum. I have posted on it before.

HTH
BrianT