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ISO15693 Read Inventory Issue Resolution - Technical Analysis

Steps taken to address the problem of extra bytes read through SPI interface on TRF796x for ISO15693 Read Inventory operation, including required modifications and root cause analysis.

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ISO15693 Read Inventory Issue Resolution - Technical Analysis

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  1. ISO15693 Analysis Erick Macias TI Confidential - Internal Only

  2. Problem Overview • ISO15693 Read Inventory: • 2 extra dummy bytes were read through the SPI interface from the TRF796x. • The problem was successfully recreated on the TRF7961 EVM as shown in the next slide.

  3. Original ISO15693 Read Inventory Root Cause Extra 2 0’s

  4. Modified ISO15693 Read Inventory Modified SPI.c

  5. Required Changes • SPI.c modifications: • Remove the reading of extra 2 bytes in SpiReadCont(). • Reset the SPI module before modifying the control registerNote: When the MCU was not resetting the SPI module it was causing the MOSI line to stay high till the next clock cycle.

  6. Required Changes (cont.) • trf796x.c modifications: • Read the FIFO status register before reading the FIFO registerNote: The TRF796x has a FIFO (12 bytes long), thus when the interrupt would fire with an IRQ status value of 0x60 – the TRF796x has received data (9 bytes) into the FIFO, but is not complete yet. However, I would recommend to read the FIFO status register first, to ensure that we read the FIFO based on the FIFO status register.

  7. Thank you

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