strange behavior when trying to read from AM2315 I2C device

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1

I am having some trouble with the AM2315 Temp\Humidity sensor. I have it hooked up to my BeagleBone Black as described below with the addition of a 10k resistor from White to red and another one from yellow to red. When its all hooked up and I run i2cdetect, it loads up to 5B really fast and then it slowly (about 1 per second, in red below) loads each address after that until it gets to the end… but never shows the AM2315 at 5C. I have tried multiple i2c buses and 4.7k resistors but get the same thing. Any ideas?

Red: 3v3
White: P9_21
Yellow: P9_20
Black: GND

i2cdetect -y -r 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: – -- – -- – -- – -- – -- – -- –
10: – -- – -- – -- – -- – -- – -- – -- – --
20: – -- – -- – -- – -- – -- – -- – -- – --
30: – -- – -- – -- – -- – -- – -- – -- – --
40: – -- – -- – -- – -- – -- – -- – -- – --
50: – -- – -- – -- – -- – -- – -- – -- – --
60: – -- – -- – -- – -- – -- – -- – -- – --
70: – -- – -- – -- – --

root@arm:~# i2cget -y 1 0x5C 0x03 b
Error: Read failed

2

The fact that this isn’t a 3.3V part may not be helping

http://www.adafruit.com/products/1293#Technical_Details - “3.5 to 5.5V power and I/O”

3

oh… This whole time I was thinking it was 3.3-5v. Thanks for pointing that out… I completely missed that. So how would I connect it to the bbb safely? Resistor divider on the data line?

4

You would want something like this.

http://www.adafruit.com/products/757

5

DeKay <darrylkacher@...> writes:

You would want something like this.http://www.adafruit.com/products/757On

Friday, 4 October 2013 06:52:28 UTC-6, jos... <at> gmail.com wrote:oh..
This whole time I was thinking it was 3.3-5v. Thanks for pointing that
out.. I completely missed that. So how would I connect it to the bbb
safely? Resistor divider on the data line?On Thursday, October 3, 2013
10:22:49 PM UTC-4, DeKay wrote:The fact that this isn't a 3.3V part may not
be helpinghttp://www.adafruit.com/products/1293#Technical_Details - "3.5 to
5.5V power and I/O"On Thursday, 3 October 2013 09:37:15 UTC-6,

I am having some trouble with the AM2315 Temp\Humidity sensor. I have it

hooked up to my BeagleBone Black as described below with the addition of a
10k resistor from White to red and another one from yellow to red. When its
all hooked up and I run i2cdetect, it loads up to 5B really fast and then it
slowly (about 1 per second, in red below) loads each address after that
until it gets to the end.. but never shows the AM2315 at 5C. I have tried
multiple i2c buses and 4.7k resistors but get the same thing. Any ideas?Red:
3v3White: P9_21Yellow: P9_20Black: GNDi2cdetect -y -r 10 1 2 3 4 5 6 7 8 9 a
b c d e f00: -- -- -- -- -- -- -- -- -- -- -- -- -- 10: -- -- -- -- -- -- --
-- -- -- -- -- -- -- -- -- 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
-- 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 40: -- -- -- -- -- --
-- -- -- -- -- -- -- -- -- -- 50: -- -- -- -- -- -- -- -- -- -- -- -- -- --
-- -- 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 70: -- -- -- -- --
-- -- --

root <at> arm:~# i2cget -y 1 0x5C 0x03 b
Error: Read failed

I don't have a Beagleboard. I am using a bus pirate to do I2C. It has an
I2C address scanner. The AM2315 would respond every other scan. Then I
looked more closely at the spec sheet and it says that you have to "wake up"
the device, then talk to it. The Spec sheet can be found at Adafruit.com
FYI, I am running at 5V with 4.7K resistors. I have not yet been able to
read data from it yet. I just got it today.