Problem with Multiple I2C devices on Due
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Problem with Multiple I2C devices on Due

by nataku on Mon Feb 17, 2014 10:10 pm

Hi,
I am having problem connecting 2 I2C devices on the Due. All shields and bidirectional level shifter from Adafruit.
The problem is like this :
I have RGBLCDShield and RTC DS1307 Shield that I want to connect into the Due.
I can only get the 2 devices communicate to the Due correctly if I connect the RTC Shield to SCL 21 and SDA 21 and the RGB LCD Shield to SCL1 and SDA1.
If I try connecting both shields on SCL21 and SDA21, then only the RTC Shield works but the LCD Shield does not work.
If I try connecting both shields on SCL1 and SDA1, then only the LCD works but the RTC Shield does not work.
If I swap the SCL21 and SDA21 so they are connected to the RGB LCD Shield, and SCL1 and SDA1 to the RTC Shield, then none of them work.

I tried them with and without pull up resistors (10K). Same results.

I am using bidirectional level shifter to go from the 5V side logic from the shields to the 3.3V side logic of the SCL and SDA inputs in the Due.

Does anyone have any clue on what to check?
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Re: Problem with Multiple I2C devices on Due

by adafruit_support_mike on Tue Feb 18, 2014 12:47 am

The symptoms are wierd enough that my first hunch is to look at the wiring. Could you post a photo of how you have things connected please?
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Re: Problem with Multiple I2C devices on Due

by nataku on Wed Feb 19, 2014 12:55 am

I am attaching the fritzing file. I is pretty close to what I have. You may have to rename the extension back to .fzz
Attachments
i2c multiple device on DUE.txt
rename extension of this file to fzz
(5.07 KiB) Downloaded 3 times
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Re: Problem with Multiple I2C devices on Due

by nataku on Wed Feb 19, 2014 12:57 am

The devices I used in the fritzing file I sent you are not exactly what I have since Fritzing does not have those equipment library model. but I think you will be able to understand my wiring. Imagine the LCD shield there is Adafruit RGBLCD and the 2 wires are the SDA and SCL inputs.
The LCD are powered using 5V. and the RTC clock also are powered using 5V from the Due. I did not show this.

Thanks.
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Re: Problem with Multiple I2C devices on Due

by adafruit_support_mike on Wed Feb 19, 2014 1:15 am

I'm looking for non-schematic information about the actual wiring and the connections. A schematic shows what you think is there, a photo of the hardware shows what's really there.
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Re: Problem with Multiple I2C devices on Due

by nataku on Thu Feb 20, 2014 12:09 am

How do you even post a jpg here?
The jpg file is not accepted as a valid file.
I just rename the jpg and upload need. You need to rename it back to jpg.
Attachments
photo.txt
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Re: Problem with Multiple I2C devices on Due

by adafruit_support_mike on Sat Feb 22, 2014 12:04 am

Thank you.

Given that setup, there are a couple of ways to share the I2C bus. You can make A1 the SCK input and connect both the RTC and LCD SCK lines to B1, and do the same with SDA, A2, and B2. You can also leave the RTC and LCD jumpers where they are and use jumpers to copy the SCK/SDA signals from A1/A2 to A3/A4.

Which version did you do when testing the connections?
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Re: Problem with Multiple I2C devices on Due

by nataku on Sat Feb 22, 2014 12:19 am

1.5.5,
I'll give it a try and I'll let you know.
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