TXB0108 logic sifter

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borgborg
 
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TXB0108 logic sifter

Post by borgborg »

I'm trying to use a TXB0108 logic shifter 3v to 5v - and all I get is 2v instead of 5v. It goes to a stepper motor controller board. Iv'e got 5 v in but only get 2v out! Any ideas??

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paulf8080
 
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Re: TXB0108 logic sifter

Post by paulf8080 »

2v is what you get when a 5v input signal in not connected. We used to call it a floater back when I worked on computers.. Check the connection and the output enable OE pin.

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borgborg
 
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Re: TXB0108 logic sifter

Post by borgborg »

no luck. I have even tried common ground with 12v supply and pi - 5v comes from motor board. also tried 5v from pi

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paulf8080
 
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Re: TXB0108 logic sifter

Post by paulf8080 »

OOPs. Sounds like I am way off. What do you mean you tried a common ground? I'm guessing, but I may have seen that problem, too. I'm guessing that if you measure the voltage between the two grounds you will see your missing 3v. You may already know this, but 5v is not an absolute. It is a potential. Meaning 5v is a difference, not an absolute, between 5v and a reference ground. When you are measuring voltage on two pieces of equipment hooked to each other the two MUST have a common ground reference to measure voltage on both sides. Leave the black probe on the voltmeter attached to one ground and measure the other.

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adafruit_support_mike
 
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Re: TXB0108 logic sifter

Post by adafruit_support_mike »

Post a photo of the hardware and your connections and we'll take a look.

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borgborg
 
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Re: TXB0108 logic sifter

Post by borgborg »

I decided to try a 5v trinket pro instead. I'll let you Know

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