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Help:PC parallel port to SPI voltage shift circuit

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smithchart

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spi voltage

Hi,

Anyone have the reference design/recommendations for an interface circuit between the PC parallel port and a device using SPI protocol? The main purpose of the interface circuit is to convert +5V output of PC parallel port to +3.3V which is going to be used by SPI protocol.

Thanks in advance.
 

IanP

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parallel port spi

Here is a simple level translator/buffer that will convert levels from, in this case, 3.3V to 5V and vice versa ..

Regards,
IanP
 

    smithchart

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smithchart

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pc parallel port spi

Hi, IanP:

Thanks a lot for your help!

It would be better if you can give more details on this figure such as suitable parts(part number) of the transistor.

Actually, after intesive searching on the Internet, I also found similar circuits that used Philips BSNxx series MOSFET to implement the general purpose bi-directional voltage shifter. In addtion, there are a lot of ICs that can achieve this kind of goal, in order to benefit everyone who viewed this post, I'd like to share some of the applications as below.

Best regards,
 

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jhbbunch

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pc port circuit

From Ian's slick little voltage translation circuit, 10 k resistors and 3.3 and 5 volt levels aren't going to generate a milliamp of current so any cheap general purpose NPN transistor like a 2n3904 of pn2222 will work fine. Any low power NPN bipolar transistor with a gain of over 100 and a current rating of over 100 milliamps should be safe (hundreds of transistors meet that criteria). That circuit is like 10 cents to make, but if you want to spend bucks on Maxims level conversion stuff be my guest.
 

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