I was thinking of using a BMP085 pressure/temp sensor with a 5V arduino and I started looking into level shifting. There are at least two breakout boards (one from Adafruit and one from Sparkfun) and a several ICs with 4050 somewhere in their names. I'm confused. I want to connect the BMP085 to the i2c bus along with a 16x4 i2c screen and DS1307 RTC both operating a 5V.
What's the best (bi-directional?) level shifter to use to connect BMP085 (which has to operate a 3.3V) to the i2c bus with the other two 5V devices?
I was thinking of using a CD74HC4050E which I think is pretty much the same as the 4050 level shifter in the Nokia 5110 tutorial.
I did that tutorial with CD74HC4050E and checked that the signal (on my DSO quad) going into the Nokia screen was getting pulses about 2/3 as big as the stuff coming out of the arduino pins. (I never bother to calibrate the DSO, b/c it seems like I get annoyed and try another firmware like every other day.) So it seems to work fine. Will this shifter work with i2c?
the best level shifter? why are there so many?
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Re: the best level shifter? why are there so many?
Have a look at the product description for our 4-channel I2C-safe Bi-directional Logic Level Converter.
It says this:
So, actually, if you're using an I2C device, our I2C-safe Bi-directional is the gizmo you want.
It says this:
The 74LVC245 is a unidirectional device similar to the 4050.We do have some other handy level shifters in the shop, from the DIP 74LVC245 to the fancy bi-directional TXB0108. However, neither of these are happy to work with I2C, which uses a funky pull-up system to transfer data back and forth. This level shifter board combines the ease-of-use of the bi-directional TXB0108 with an I2C-compatible FET design following NXP's app note
So, actually, if you're using an I2C device, our I2C-safe Bi-directional is the gizmo you want.
Please be positive and constructive with your questions and comments.