I'm following the Initialization Sequence in the Applications Section 10.4 of the Data Sheet. ( http://www.ti.com/product/ADS131A04/datasheet/ Everything is good up until I issue the UNLOCK command. The device always spits out the same thing... 0xFF04. I never see 0x2204 ( or x0655 i.e. UNLOCK ACK response) I have checked all SPI signals against the timing spec's (i.e. CS, SCK, MISO, MOSI) and everything looks in order. I'm using the STM32F407 processor to communicate with the ADS131A04 . The STM32F407 SPI is configured and operating as follows: // Initialize SPI1 registers SPI_InitTypeDefStruct.SPI_Direction = SPI_Direction_2Lines_FullDuplex; SPI_InitTypeDefStruct.SPI_Mode = SPI_Mode_Master; SPI_InitTypeDefStruct.SPI_DataSize = SPI_DataSize_16b; SPI_InitTypeDefStruct.SPI_CPOL = SPI_CPOL_Low; SPI_InitTypeDefStruct.SPI_CPHA = SPI_CPHA_2Edge; SPI_InitTypeDefStruct.SPI_NSS = SPI_NSS_Soft; SPI_InitTypeDefStruct.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_8; SPI_InitTypeDefStruct.SPI_FirstBit = SPI_FirstBit_MSB; SPI_Init(SPI1, &SPI_InitTypeDefStruct); I'm sending the proper ULOCK command (i.e. 0x0655) MSB first. The SCK period and pulse duration's are in spec per the ADS131 data sheet (Section 7.10 Timing Requirements for Synchronous Slave Interface Mode) The ADS131 only supports SPI mode 1 ( CPOL = 0 and CPHA = 1 ). My STM32 SPI initialization is doing that correctly. I don't see any obvious hardware or firmware errors. Thoughts?
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