what is the purpose NSBC114EDP6 IC in tx pin

[Iraianbu]

I try to debug the circuit here I face a problem that the transmitter pin from MCU is connected to the NSBC114EDP6 (SMD marking code 7A) input pin 2 and the output pin from pin 3 is connected to another MCU receiver pin.

I have scoped the input and output data form the IC NSBC114EDP6. There is no voltage difference and i have attached scoped image below.

channel_1 (yellow) - Input NSBC114EDP6 IC
channel_2 (green) - output NSBC114EDP6 IC

I want know what is the purpose of using NSBC114EDP6 IC.

 

[KlausST]

Hi,

There´s something wrong here.

NSBC114EDP6 has no "input" nor "output" ... To avoid confusion I recommend to use pin names as shown in the schematic / datasheet.

Next is that the scope shows both voltages above 3.6V, while the STM32 is specified for 3.6V only.

So please provide more details. Like application information, where the circuit is from, is it a real circuit at all. Maybe some photos (100kBytes should be sufficient).

Klaus

 

[FvM]

I want know what is the purpose of using NSBC114EDP6 IC.

Ask the guy who created the schematic.

I try to debug the circuit here I face a problem that the transmitter pin from MCU is connected to the NSBC114EDP6 (SMD marking code 7A) input pin 2 and the output pin from pin 3 is connected to another MCU receiver pin.

Which problem?

It's a dual "digital" transistor. Two inverting buffers are producing a non-inverted copy of the input signal, not surprizing so far.

--- Updated Oct 7, 2022 ---

There´s something wrong here.

Not particularly, just a badly readable schematic.

Next is that the scope shows both voltages above 3.6V, while the STM32 is specified for 3.6V only.

That's how Proteus works. It does functional, not electrical simulation of uC, assuming a default logic voltage of 5V. You can probably edit the logic voltage, don't know I'm not so interested in the details of this tool.

 

[KlausST]

Hi,

Not particularly, just a badly readable schematic.

I did understand the schematic.
I miss this "the output pin from pin 3 is connected to another MCU receiver pin."
But I guess I have misinterpreted it as "another pin on the same MCU".

Even on "another MCU", it would be informative what exact MCU and it´s power supply.

That's how Proteus works.

Is the "Keysight scope" a proteus tool? I thought it is a real scope.

Klaus

 

[FvM]

Is the "Keysight scope" a proteus tool? I thought it is a real scope.

Good point. I guess STM32 is just a dummy CPU, real circuit uses different TxD source.

Anyway, we don't know what the actual problem is. The circuit is operating as expectable, why they inserted the buffer - we don't know.

 

[KlausST]

Hi,

my idea: a level converter.
But the given scope view then makes no sense.

Klaus

 

[FvM]

A possible explanation would be a wired AND connection of multiple outputs to create a kind of "poor mans" UART bus, also the pull-up resistor series diode is suggesting this interpretation.

 

[Iraianbu]

Good point. I guess STM32 is just a dummy CPU, real circuit uses different TxD source.

Anyway, we don't know what the actual problem is. The circuit is operating as expectable, why they inserted the buffer - we don't know.

Yes STM32 is dummy mcu

 

[KlausST]

Hi,

so ...
Neither the schematic is correct / complete
nor the scope picture is valid?

Nor do you want to provide missing informations?

I like to help, but how can I?

Klaus