Active low transmitter question

[mpgmike]

I suppose it boils down to how much "oomph" the transmitter packs. If it's a weak signal, it may not be able to overcome the 10k pull-up. If it has sufficient amp capability, then you're golden. The best answer will be given from your test. It either works or it doesn't. As posted, not enough information to go on.

[LEDave]

Thanks for the reply mpgmike

Wouldn't making pin3 on the pic go low for say 50ms make the transmitter which transmits when 'active low' transmit as the Tx pin on the transmitter is on the same line as the pic pin3 set Output LOW 50ms in code?

[mpgmike]

WHAT??? Your transmitter is "Talking" and your PIC should be "Listening"; or receiving. In order for your PIC to receive/listen, your pin3 must be configured as a digital (ANSEL Register reads 0 for that pin) input (TRIS Register set to 1 for that pin). For you to have your PIC make that transmission line low, you have to clear the TRIS bit to make it an output, then use either the PORT or LAT Register to make the pin3 low.

WHAT DOES ANY OF THIS HAVE TO DO WITH RECEIVING A TRANSMISSION??!!?!?!??? What do you hope to accomplish??

[LEDave]

"WHAT DOES ANY OF THIS HAVE TO DO WITH RECEIVING A TRANSMISSION??!!?!?!??? What do you hope to accomplish??"

mpgmike - I've never mentioned or talked about 'RECEIVING A TRANSMISSION??!!?!?!???' Exactly the opposite. I'm asking if pin3 on the pic is pulled low in code, there will be a wire from pin3 on the pic to the Tx pin on the RF transmitter, the transmitter operates when the Tx pin goes low so I'm asking if I pull pin3 LOW for say 50ms that should make the transmitter transmit.

All I'm trying to do is replicate and replace a push button from the transmitter Tx pin to ground by using a pic to send the Tx line LOW. The 10k resistor being added to keep the line High to stop any floating voltage causing a 'false' transmit.

[mpgmike]

If your question is, "Can the PIC safely overcome the 10k pull-up resistor?", the answer is absolutely yes. Again, will it do what you want, you'll just have to try it and see.

[LEDave]

Thanks for your help mpgmike, anyone else have any thoughts on this?

[richard]

anyone else have any thoughts on this?

using a resistor to drive a pin to a default logic level is not an uncommon practice.
so common that i would not be surprised that your [type not disclosed ] transmitter has such a pullup
resistor already installed. the only reason i could see for an additional pullup would be if the pic was routinely disconnected
from a device that did not have a built in pullup or that an open drain/collector pic pin was in use.
summing up with the detail[almost non existent] you have provided it seems to be a pointless waste of a component
that could easily be eliminated with good programming practice.