Interfacing SPI between SBC MC33905S5 and MCU MPC5643L without Levelshifters

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Interfacing SPI between SBC MC33905S5 and MCU MPC5643L without Levelshifters

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ahauschild
Contributor I

Hello,

I am new to the forums and currently developing a customized hardware based on the MTRCCBP5643L.

Key elements in this DevKit are the SBC MC33905CS5 (VDD=5V) and MCU MPC5643L.

While checking the reference schematic I noticed that the SBC is interfaced directly to the MCU and checked the datasheets for voltage levels. It seems to me, that the voltage levels of the SBC for SPI are referred to VDD: 0,3xVDD=1,5V for Logic Low and 0,7xVDD=3,5V for Logic High.

The only information I found for the MCU are that all I/Os have the same voltage as the external supply (3.3V nominal).

Under normal circumstances I would assume that levelshifters (5V<->3.3V) would be needed.

Is there an explanation why there are none in the reference design? Did I miss anything explanatory/ crucial in the datasheets?

Regards

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lukaszadrapa
NXP TechSupport
NXP TechSupport

Hi,

it looks like serious mistake in the design. You are right, this version of SBC is 5V, MPC5643L is 3.3V only. The SPI signals and also CAN/LIN signals should not be connected directly.

The author of this design is not working for this company anymore but I will ask the apps team if they are aware of this issue.

Regards,

Lukas

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