Unusual serial comunication

[mat janssen]

maybe this is what you need.
Make the communication so that if there is no communication the powersupply is 5 volt.

[MegaADY]

Thanks for your schematic. It does not work ... in fact I have some curent pulses in the collector of BC547 ... but no valid data . I am using T300 picbasic mode. Any ideea where the problem might be ?

[mat janssen]

Then put a big capacitor in the neighborhood of the BC547. The collector resistor of the bc547 must be at the stable site of the supply.
The 2x100 ohm resistors for the data switch might be higher in value if the supply current of the PIC1 is low.
You have to play with it, because I don't know what you are making. It was yust an example of an idea.

[MegaADY]

Thank you , it is working finally, I put 26ohm resistors instead of 100ohm.
The pics are communicating to each other, but the main slave device, don't.
It doe not have enough power ! The slave device is powered by the master device with 5v and it drains about 500mA. Pic1 inside the slave device is satisfied with 3v but the main device don't ... hmmmm .... what can I do in this situation ?

[mat janssen]

The main pic gets alway's 5 volt or did you make an other circuit than I drew?
Or your 7805 is broken. or your main supply is not strong enough.
Or did you build sommething else. if so please let me see the drawing then.

[MegaADY]

hm .. can I talk with you ? Can you give me a messenger address where I can explain you everyting more detailed ? thank you

[mat janssen]

I don't have a messenger adres. Only an email adres.