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FRDM-KEAZ and SPI

Question asked by Walter Appel Employee on Feb 16, 2016
Latest reply on Feb 19, 2016 by xiangjun.rong

Sorry if this is not an appropriate forum for this question. If there is a better place to post it, please let me know.

 

I am using a FRDM-KEAZ128Q80 to create a sample SPI program that uses the SPI0 module in master mode to get data from a Bosch BMP280 pressure sensor slave. An example of the type of operation I need to do is read a series of registers in the pressure sensor. It should be pretty easy because on register reads, the pressure sensor receives a control byte (the register address), then it autoincrements and sends the register contents for the first register and any subsequent registers until the chip select signal goes high.

 

Unfortunately, the Kinetis SPI module tends to set the chip select to high between transmissions. How can I either force the chip select to stay low or use a GPIO as the chip select. I am sure I am missing something really obvious but when I setup an GPIO as a chip select, how do I trigger the SPI module to activate its output clock, serial data out, and serial data in pins?

 

Thanks in advance for any guidance!

 

Walt

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