USB Rx/Tx LED indicator

[debojitacharjee]

I need to make a LED light up whenever there is a data transfer between a USB storage device and the PC.

During the data transfer the voltage in the Rx/Tx lines is about 1 volts.

So, how do I make an LED light up after detecting that voltage?

Can it be done using a MOSFET?

 

[Harald Kapp]

USB has no Tx/Rx. USB is bidirectional using D+ and D-.
Do you mean the UART interface that is used together with a UART<>USB converter on many microcontroller boards (e.g. Arduino)?

 

[Harald Kapp]

This thread my interest you.

 

[debojitacharjee]

USB has no Tx/Rx. USB is bidirectional using D+ and D-.
Do you mean the UART interface that is used together with a UART<>USB converter on many microcontroller boards (e.g. Arduino)?

I mean the data lines (D+, D-), and whenever there is a data transfer, there is a voltage flow. So, I need a simple circuit that will make the LED glow when voltage will flow in the D- and D+ lines.

 

[Harald Kapp]

there is a voltage flow.

Voltage doesn't flow. Electrons flow which is called current.

You will have to monitor the voltage differential (V_D+ - V_D- fpr activity, e.g. using a comparator. Then use the output of the comparator to drive an LED. Possibly a monostable multivibrator could be added to keep the LEd on for a longer time to increase visibility.

However, you will not get information about actual data transfer over the USB connection as USB is a polling protocol and there wil be constantly data traffic even without any actual payload data being transferred, see e.g. here. You will not be able to distinguish between payload data and polling packets.

 

[debojitacharjee]

Voltage doesn't flow. Electrons flow which is called current.

You will have to monitor the voltage differential (V_D+ - V_D- fpr activity, e.g. using a comparator. Then use the output of the comparator to drive an LED. Possibly a monostable multivibrator could be added to keep the LEd on for a longer time to increase visibility.

However, you will not get information about actual data transfer over the USB connection as USB is a polling protocol and there wil be constantly data traffic even without any actual payload data being transferred, see e.g. here. You will not be able to distinguish between payload data and polling packets.

Thanks! I know electrons flow but that was just a unofficial language of mine. I don't want to monitor the packets of the data lines but I jest need an indicator whenever there is a data transfer. So, do you know the circuit diagram for that? Can it be done using a MOSFET or is there any IC for this?

 

[Harald Kapp]

that was just a unofficial language of mine.

Please use the official language of the trade. No one else here knows your personal lingo.

I jest need an indicator whenever there is a data transfer.

Understood. But as stated before: on USB there is constantly data transfer because it is based on polling. An LED indicator will not be of much use. You will need a USB analyzer to distinguish between the periodic polling packets and the payload data.

you know the circuit diagram for that?

I have no diagram for this.

Can it be done using a MOSFET

Most certainly.

is there any IC for this?

I doubt it. I don't know one, which doesn't mean there isn't one.

 

[Delta Prime]

Oh, this is homework and you gave him all the answers!

 

[debojitacharjee]

Oh, this is homework and you gave him all the answers!

No, he didn't. He only gave me some clues but it's not a complete solution to my homework. Without a circuit diagram it can't be that easy.

 

[Delta Prime]

No, he didn't. He only gave me some clues but it's not a complete solution to my homework

My gratitude for the correction.
I shall be more diligent in the future.