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I'm using the Raspberry PI to communicate with various sensors and other circuits that input and output 5V logic level. The Raspberry Pi itself has 3.3V GPIOs, so i need to convert the logic levels.

I found the following chip, with this capability: http://www.farnell.com/datasheets/1635559.pdf

I'm quite new to hardware development and would like to know if I have to purchase any other components to use this chip. The datasheet mentions pull-up resistors for instance.

I also found this ready to go chip that I think uses the same component. I can see various other components on it, but I would like to use the breadboard version :

http://ee.farnell.com/adafruit-industries/395/logic-level-converter-8ch-arm-development/dp/2301650?dimVals=110514096

Can anyone provide me with a circuit to hook up the SN74LVC245AN safely and effectively on a breadboard.

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  • \$\begingroup\$ Do your GPIOs ever change between input and output? \$\endgroup\$ – Ignacio Vazquez-Abrams Nov 1 '13 at 21:01
  • \$\begingroup\$ Also, the breakout uses a completely different chip. \$\endgroup\$ – Ignacio Vazquez-Abrams Nov 1 '13 at 21:03
  • \$\begingroup\$ During operation I don't intend to change GPIO modes from input to output. I use different GPIO pins for input and output. I do however think I need two of these chips, 3.3v to 5v and vice versa. \$\endgroup\$ – Ollusaurus Nov 1 '13 at 21:28
  • \$\begingroup\$ The '245A won't help you then, since it won't do 3V3 and 5V output at the same time. Look at the '07 or TXB01nn instead. \$\endgroup\$ – Ignacio Vazquez-Abrams Nov 1 '13 at 21:31
  • \$\begingroup\$ As I understood the '245A can do conversion both ways (not at the same time.) I can use two of these chips and get the job done. The main problem is that I don't know what kind of circuit to use with the chips. \$\endgroup\$ – Ollusaurus Nov 1 '13 at 21:44
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Sparkfun has two logic level translator boards. One is $3.95 and the other $6.95. The cheaper one is based around the TI TXB0104 chip, and has 4 bi-directional channels. I have successfully used this chip in a commercial product where I had to translate back and forth between 3.3v to 1.8v for a cell module.

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I wouldn't think pull-up resistors would be needed unless you are using an I2C bus. Their site has a nice hookup guide for this breakout board, including a sample for connecting a device to an Arduino. Note: Just opposite of what you are trying to do, since the Arduino is 5v and the peripheral is 3.3v)

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