Basic Question: LED to see a signal

[KansaiRobot]

Hello and thanks always

Other than doing the projects I do (and in which I get so much help from you guys, always appreciate it) sometimes I have very basic questions. I would be grateful if someone can help me on this too.
They are very basic questions though.

In this occasion, I would like to ask about this situation

Say I have two ICs, or an IC and a component. One of the pins of part 1 is connected to one pin of part 2.
Part 1 transmit a 1 or a 0 uinidirectionally to part 2

My question is: How can I put a LED there, so that this indicates me when a 1 is being transmitted??

The parts I am using is a 3.3 V PIC for part 1 but the question is in general for a 5V PIC or any other component. Part 2 this time is a LCD, but again the question is in general

 

[audioguru]

The datasheet for the LED you want to use tells you its range of forward voltage and its maximum allowed current.
The datasheet for the PIC you want to use tells you how much is its output voltage and current.
See if they can go together with a series current-limiting resistor and make the LED bright enough.
If the LED is not bright enough then add a transistor to drive it.
It the duration that the LED is turned on is less than 30ms then it appears dimmed. Add a pulse stretcher to make it bright.

 

[KansaiRobot]

Thank you.
You mean something like this?

by the way, can I do something like the line with the oscilloscope to see the signal? I guess I can, just asking just in case

 

[audioguru]

Why does your block diagram show TWO microcontrollers but no power supply?
Why does your oscilloscope have only one input wire?

 

[KansaiRobot]

Why does your block diagram show TWO microcontrollers but no power supply?
Why does your oscilloscope have only one input wire?

Oh, I just made the draw to illustrate my point. (ergo, no power supply, oscillators, etc). I am connecting one pin from the left to the B0 pin of the PIC and transmitting 1's on left-right direction. (wanted to make sure I understood what you explained about the LED

about the oscilloscope, the input wire connects to the pin and ground wire connects to ground.

 

[JimB]

A bit more like this:

JimB

 

[audioguru]

When your microcontroller is loaded by the LED's current, is its voltage high enough to be a logic 1 to the PIC?
The datasheet of the PIC will say what is its minimum input high voltage and your oscilloscope will show the actual voltage.
Then you should also measure the actual voltage at RB0.
What is the duration of the pulses?

 

[KansaiRobot]

A bit more like this:

View attachment 95550


JimB

really?! You mean a LED in parallel?? going to ground... thank you I will experiment with that

 

[audioguru]

Of course the LED must be connected to ground if its current-limiting resistor is powered from a logic "1".