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LPC51U68: Need help with SPI slave bytes shift issue

Question asked by John Zhou on Oct 31, 2019
Latest reply on Nov 7, 2019 by xiangjun.rong

Hello my friends:

 

I’m new for LPC51U68. Now I’m migrating from LPC111x to LPC51U68 and encounters some issues, one of major issue is SPI slave byte shift.

 

Environment:

1.Modified LPC1114 example SSPMaster, sends 64 Bytes per frame and 82ms idle between 2 frames(in a while loop).

2.Modified LPC51U68 NXP example spi_polling_b2b_transfer_slave ,64 Bytes per frame, and data starts from 0x00, 0x01 till 0x3F. I also put transfer statements into while loop.( following screen capture shows what I have changed from the original file)

3.Connect LPC1114 Pin 0.6 to LPC51U68 P0.11, and conn P0.4 on LPC51U68 to GND and power up both boards then captures transfer with Saleae.

 

51U68 slave data always shifts header byte(1 or 2 bytes) from the second transfer in while loop.(Only 3rd frame corrects one time)

 

 

How can I fix this make SPI slave always starts from 0x0 and ends with 0x3F? Thanks a lot!

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