Datalogger shield with 3.3v i2c devices

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brimus
 
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Joined: Sun Aug 07, 2011 2:35 am

Datalogger shield with 3.3v i2c devices

Post by brimus »

Reading on the BMP085 i2c page it is a 3.3v device. The RTC (DS1307) is a 5v i2c device. I plan on using the data logger shield , a BMP085 and the TSL2561 all together. The pages for the BMP085 and TSL2561 state to remove the pull up resistors that are on the data logger for the 5v RTC. From the schematic it appears that R1 and R2 are the resistors that need to be removed. I want to verify this before I start modifying the board as it works fine now without the other i2c devices.

Also I wat to verify that once I remove the resistors that I should not run the data logger without one of the other i2c devices or it may damage the RTC. Is there a way to be able to use or not use the 3.3v i2c devices with the data logger without having to worry about the RTC ?

Do you know of a humidity i2c device? I have not found one on your sire nor on any other but would like to get one rather than use the DHT22 digital device.

I hope these questions made sense.

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adafruit_support_bill
 
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Re: Datalogger shield with 3.3v i2c devices

Post by adafruit_support_bill »

R1 and R2 are the pullups. Trying to run without them should not cause damage to the RTC.

The SHT11 humidity sensor uses a similar 2-wire interface that is only partly compatible with the i2c bus.
http://forums.parallax.com/showthread.p ... on-I2C-bus

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