To be fully on safe side it makes sense to apply voltage buffers between 2.5 V and 3.3V
signals. But one can try to analyze carefully acceptable low and high voltage levels of the signals,
using their hardware specs : perhaps there are no problems. For example - minimal output
high voltage level of 2.5V part is greater than minimal input high level of 3.3V device.
Have a great day,
Yuri
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