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Altera_Forum
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12 years ago

Getting data from a rtc device through I2C

Hi all, I would like to retrieve information from a RTC device which is directly connected to a GPIO, using the i2c protocol. So, the first step was to load the i2c-gpio driver with this piece ...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
12 years ago

Hi,

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So I eventually succeed in detecting my i2c device (RTC) despite I still get some half-amplitude i2c signals. Actually it was not a software issue but rather a FPGA configuration problem. To explain it simple:

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If you still observe the half-amplitude i2c signals on your SDA, I strongly recommend you to check again whether your SDA pin is open-drain or not. The half voltage at the ACK phase means that someone is driving your SDA line high despite your rtc is driving it low. In normal case, only the pull-up resistor can make the SDA line high and it's force is not so strong because you are using 4k7.

Kazu