I want to detect that the esp32 is outputting the signal out of the intended pin.

The following circuit will light up both LEDs if its input has both high and low signals. It can be implemented using any one of a number of IC chips with multiple inverters capable of driving LEDs.

^{simulate this circuit – Schematic created using CircuitLab}

There are many variations that can be made to this circuit.

Depending on the logic family, it may be implemented with only two inverters. The example I show uses four because a) there are many IC chips that have multiple inverters and the cost of using an extra inverter is small and b) there may be concern that the LEDs will load the output of the inverter preventing it from properly triggering a following stage, so LEDs are only connected to "final" stages.

In some cases, one may want to place a current limiting resistor in series with the LEDs. I have used a circuit such as this using LSTTL logic, and never bothered with resistors. It worked fine. But if the LEDs are particularly power hungry, or if the logic family has "weak" outputs, you may want to use resistors.

Also, in some cases, it may be preferable to connect the LEDs to Vcc and have the inverters sink current, rather than source it. It all depends on what kind of inverters you have available.

Another useful circuit is to have a few parallel out counters, such as 74xx590's driving LED bar displays. Each LED bar will toggle on and off, but as one moves through the frequency dividers, the frequency gets lower, and eventually one reaches a point where the toggling is visible. This can give an indication of the frequency of the digital signal.

I want to detect that the esp32 is outputting the signal out of the intended pin.

The following circuit will light up both LEDs if its input has both high and low signals. It can be implemented using any one of a number of IC chips with multiple inverters capable of driving LEDs.

^{simulate this circuit – Schematic created using CircuitLab}

There are many variations that can be made to this circuit.

Depending on the logic family, it may be implemented with only two inverters. The example I show uses four because a) there are many IC chips that have multiple inverters and the cost of using an extra inverter is small and b) there may be concern that the LEDs will load the output of the inverter preventing it from properly triggering a following stage, so LEDs are only connected to "final" stages.

In some cases, one may want to place a current limiting resistor in series with the LEDs. I have used a circuit such as this using LSTTL logic, and never bothered with resistors. It worked fine. But if the LEDs are particularly power hungry, or if the logic family has "weak" outputs, you may want to use resistors.

Also, in some cases, it may be preferable to connect the LEDs to Vcc and have the inverters sink current, rather than source it. It all depends on what kind of inverters you have available.

Another useful circuit is to have a few parallel out counters, such as 74xx590's or 74HC4040's driving LED bar displays. Each LED bar will toggle on and off, but as one moves through the frequency dividers, the frequency gets lower, and eventually one reaches a point where the toggling is visible. This can give an indication of the frequency of the digital signal.

I want to detect that the esp32 is outputting the signal out of the intended pin.

The following circuit will light up both LEDs if its input has both high and low signals. It can be implemented using any one of a number of IC chips with multiple inverters capable of driving LEDs.

^{simulate this circuit – Schematic created using CircuitLab}

There are many variations that can be made to this circuit.

Depending on the logic family, it may be implemented with only two inverters. The example I show uses four because a) there are many IC chips that have multiple inverters and the cost of using an extra inverter is small and b) there may be concern that the LEDs will load the output of the inverter preventing it from properly triggering a following stage, so LEDs are only connected to "final" stages.

In some cases, one may want to place a current limiting resistor in series with the LEDs. I have used a circuit such as this using LSTTL logic, and never bothered with resistors. It worked fine. But if the LEDs are particularly power hungry, or if the logic family has "weak" outputs, you may want to use resistors.

Also, in some cases, it may be preferable to connect the LEDs to Vcc and have the inverters sink current, rather than source it. It all depends on what kind of inverters you have available.

I want to detect that the esp32 is outputting the signal out of the intended pin.

The following circuit will light up both LEDs if its input has both high and low signals. It can be implemented using any one of a number of IC chips with multiple inverters capable of driving LEDs.

^{simulate this circuit – Schematic created using CircuitLab}

There are many variations that can be made to this circuit.

Depending on the logic family, it may be implemented with only two inverters. The example I show uses four because a) there are many IC chips that have multiple inverters and the cost of using an extra inverter is small and b) there may be concern that the LEDs will load the output of the inverter preventing it from properly triggering a following stage, so LEDs are only connected to "final" stages.

In some cases, one may want to place a current limiting resistor in series with the LEDs. I have used a circuit such as this using LSTTL logic, and never bothered with resistors. It worked fine. But if the LEDs are particularly power hungry, or if the logic family has "weak" outputs, you may want to use resistors.

Also, in some cases, it may be preferable to connect the LEDs to Vcc and have the inverters sink current, rather than source it. It all depends on what kind of inverters you have available.

Another useful circuit is to have a few parallel out counters, such as 74xx590's driving LED bar displays. Each LED bar will toggle on and off, but as one moves through the frequency dividers, the frequency gets lower, and eventually one reaches a point where the toggling is visible. This can give an indication of the frequency of the digital signal.