ST25R3914-AQWT MISO signal is shifted to 1.2V

I am Using ST25R3914-AQWT NFC chip as a Slave Device and Renesas RL78 as Master device for SPI communication.

When I tried to interface both controller MISO signal is shifted to 1.2V

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Best answer by Travis Palmer

Hello PSHAH.1,

A schematic diagram would be indeed helpful.

Our chip sets typically have the VDD_IO supply. It sources the internal level shifter. VDD_IO should be at the MCUs SPI level.

e.g. if the MCU is running at 3.3V, also VDD_IO should be put to 3.3V. VDD of the ST25R can be set to any value specified in the datasheet.

If the MCU is supplied via 3.3V and VDD_IO is driven by 5V, it could explain a shift in the MISO signal.

please let me know, if this helped!

BR Travis

Graduate II

Would suggest you're wiring it wrong.Show a wiring diagram or schematic.

ST Employee

A schematic diagram would be indeed helpful.

Our chip sets typically have the VDD_IO supply. It sources the internal level shifter. VDD_IO should be at the MCUs SPI level.

e.g. if the MCU is running at 3.3V, also VDD_IO should be put to 3.3V. VDD of the ST25R can be set to any value specified in the datasheet.

If the MCU is supplied via 3.3V and VDD_IO is driven by 5V, it could explain a shift in the MISO signal.

please let me know, if this helped!

BR Travis

Visitor II

Thank you for reply this issue is resolved. there was some stack issue now SPI is working perfectly ok

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