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Topic: Problem with TXS0108E Logic Level converter (Read 839 times) previous topic - next topic

TomGeorge

Hi,
Can you please post your code and a picture of your project so we can see your component layout?

Thanks.. Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

psychoboss


dlloyd

#17
Nov 22, 2020, 06:41 am Last Edit: Nov 22, 2020, 06:46 am by dlloyd
The response from here seems really helpful ...

These chips are not as simple as they seem because they have to sense which side is driving the signal and change direction as required. Both sides have pullup resistors so you will see high levels on all the pins even with no inputs.

Unless you actively drive one side low, the chip may think that pin is an output. So grounding input A should drive B low and grounding input B should drive A low. Anything else results in a high on both A (3.3V) and B (5V).


I think the "B" pins need to be persuaded to be inputs.
As a test, disconnect B1 from the Arduino and connect it to GND, then power up the device ... does A1 read  low (0V)?

If it does read low, then instead try a 1K pulldown resistor from B1 to GND, then power up the device ... does A1 read  low (0V)?

If it does read low, then reconnect B1 to the Arduino (do not remove the pulldown resistor). Test your code ... does the PWM signal pass through?

If it does, then you could probably eliminate the pulldown resistor and just initially drive the signal low in your setup prior to starting the PWM.

Did you try reply#9? (6v6gt)
See question by TomGeorge.

psychoboss

I connected it like you said. The Output(B) side drives the pin always low, no matter how the other pins are connected.

dlloyd

Quote
I connected it like you said. The Output(B) side drives the pin always low, no matter how the other pins are connected.
If you mean B1 drives A1 low, no matter how the other pins are connected, then that's great news!


From your original post...
Quote
There was no output at the low voltage side all the time.
I assumed here that the converter pulled the outputs constantly high (3.3V) on the low voltage side. Right?

psychoboss

Nope, the converter pulled it always low

nimo

#21
Dec 16, 2020, 01:15 am Last Edit: Dec 16, 2020, 01:44 am by nimo
So you tried this?

I tried this and it worked.... I have spent so many hours trying to "debug" this and actually ended up using a logic level shifter (4 input) for an earlier project.
This worked right out of the bat for me. I had earlier tired OE floating, OE pull up, OE pull down.... Just had never though of connecting OE both to 3.3V as well as GND (Via resistor).

PS: I am not using an arduino, it is being driven off an ESP8266, if that matters.

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