The progress on SPI has been held up by waiting for hardware. We finally found and purchased solderless headers. Once those arrive I should be able to finish setting up the connection between the chip and the Raspberry Pi.
This week I read papers on the multilateration algorithm.
Next week I will be working on the multilateration algorithm. And depending on when the solderless headers arrive I might be able to finish getting the communication between the chip and the Raspberry Pi working.