Reading signal from open drain connected to LED

[okw]

I'm trying to read the value of a charge status pin (TP4056, charge done, open drain) with LED are connected. LED anode is on the TP4056 VDD rail (USB, 5V), as I don't want the LED to draw anything when USB is not connected. However, I'm reading 2.56V when charging (status is low, LED lit) and 2.01V when charge is done (stauts floats, LED dark).
How do I solve it so MCU can read a proper low, without affecting the LEDs?

[Benta]

Put a 47 kohm resistor between your test leads, redo the measurement and come back with the voltages you measured.

[okw]

2.194V (charging) and 1.987V (done).

[Someone]

2.194V (charging) and 1.987V (done).

Seems like you'll need to provide significantly more detail. Why do you expect the chip to do anything specific when USB is not connected?

How can a pull down read a higher voltage when pulled down than when floating?

I'm reading 2.56V when charging (status is low, LED lit) and 2.01V when charge is done (stauts floats, LED dark).

[okw]

Seems like you'll need to provide significantly more detail. Why do you expect the chip to do anything specific when USB is not connected?

I don't expect that. And I don't care about the status when USB is not connected. I only care whether the battery is getting charged or not when USB is connected.

How can a pull down read a higher voltage when pulled down than when floating?

That's why I posted Nothing else is on the signal (i used to have a 200k 3.3V pull-up, but removed it). The charger (TP4056) STDBY pin --> 1k (and LED up to VCC 5V) --> MCU.
If I remove the LED it reads correct, battery in reads high, and out low.

[Someone]

How can a pull down read a higher voltage when pulled down than when floating?

That's why I posted Nothing else is on the signal (i used to have a 200k 3.3V pull-up, but removed it). The charger (TP4056) STDBY pin --> 1k (and LED up to VCC 5V) --> MCU.
If I remove the LED it reads correct, battery in reads high, and out low.

You'll need to draw a schematic of exactly what configuration you have, and details of how you're taking the measurement. Photocurrent would tend to pull the open collector up not down.

[okw]

The MCU_CHARGE_DONE goes directly to the ESP32-C3. I also have a DW01 protection circuit, which I omitted for readability.

[pcprogrammer]

That is what you get when you measure between the series resistor and the LED. Connect it like shown in the attached image and you will measure ~0 when the LED is lit.

[okw]

Thanks so much.
By the way, I see dim flickering on the red LED when charging is finished (it should be completely off). Not sure if the TP4056 is from a bad batch or what's going on. I guess they're all knock-offs anyway...
Any trick to mediate this?
Could it be cause it's connected directly to the ESP32-C3?