I2C8 level-shifted to 3.3V

Another question, this time mostly idle curiosity.

Almost all GPIO/I2C/SPI is routed directly from the RK3399 to the Edge fingers without level shifting. One exception is I2C8 which you level-shift from 1.8V to 3.3V before you bring it out on EF1 and the FPC connector.

Is there a reason for doing this - did you have a specific application in mind for I2C8?

Slightly surprising consequence is that of 11 IO lines on the FPC connector (and therefore the Edge IO), there are three different voltage conventions: 4 GPIO and an SPI at 1.8V, 2 GPIO at 3.0V and a dedicated I2C bus at 3.3V.

1 Like

Hi Chris:
The reason why I2C8 need to shift to 3.3V is because the MCU need 3.3V level:

We define the FPC connector with both 1.8V, 3.0V and 3.3V for simple expandable board like Edge-IO or other applications with just FPC cable instead a carrier board over the MXM3 connector(higher cost)

Have fun!


Aha! I missed that. Makes sense, thanks!