power line communication project

[milanino]

I am doing a PLC Project.
I use the PLC modem LM1893 and microcontroller 18f458 . The LM1893 work with frequency until 125KHZ
I don't know what is the frequency of the data send from the µPic to the Lm1893 it must be 125khz ??
please help

 

[Kripton2035]

if I remember you can go to 1200 bauds with this circuit
in fact not more than 1/10th of the carrier (but it's still too much for that circuit)
please note that the lm1893 is an obsolete circuit.

 

[milanino]

What's mean obsolete circuit??
i need to know if the quartz of the µpic must be 125khz so that this data will be adaptable with the Lm1893

 

[Kripton2035]

no the pic has its own quartz 8 - 16 20 MHz.
the lm1893 has a RC local oscillator to make a 125KHz - look at the datasheet.

 

[milanino]

it means i only link the pic and the lm1893 without adjust the frequency ??

 

[Kripton2035]

you use the uart of the pic (pins tx and rx) and you set the baud of the uart to 1200 maximum (300 is less error)

 

[milanino]

i link the tx of the pic in the data in of the lm1893 and the rx with data out ??
It's only what i need?? there are no adjustements for the frequency or other parameters??

 

[Kripton2035]

think of the lm1893 as a tunnel over the mains wiring.
on the other lm1893 you will have the signals you entered on the first lm1893
the two pics must know how to talk to each other
but the pic just have to talk at a lower (< 1/10th) frequency than the lm1893
the lm1893 datasheet says it can handle up to 4800 baud (but surely with 500KHz carrier frequency)
so if you stay at 1200 or even 300 baud it will be ok

 

[milanino]

i work with 1200 baud in the two pics . right??

 

[Kripton2035]

yes and if 300 baud between the pic is fast enought for your application, then go for it you will less framing errors.