CC2640R2F: SPI receive the same data every time (it's the register who_am_i)

Hi Tania,

What SPI parameters are you using?  Please reference the spimaster example and SPI TI Driver reference. The transferMode should be SPI_MODE_BLOCKING based on the code you've provided thus far.  I highly recommend using a logic analyzer or oscilloscope to monitor your SPI lines.  What is received if registers other than WHO_AM_I are read first?  Try switching the order to view its effect, and/or evaluate the addition of a delay between SPI reads.

Regards,
Ryan

Hi Ryan,

I'm using this parameters:

SPI_Params_init(&spiParams); // Initialize SPI parameters
spiParams.transferMode = SPI_MODE_BLOCKING;
spiParams.mode = SPI_MASTER;
spiParams.bitRate = 400000;
spiParams.dataSize = 8;
spiParams.frameFormat = SPI_POL0_PHA0;

and for each register the receive is who am i register (0x33).

Best regards,

Tania

The LIS2DH datasheet SPI slave timing diagram suggests a SPI_POL1_PHA1 format, which is why visually recording and observing the SPI communication could effectively debug this interface.  Have you interacted with this accelerometer before using a different master device, or do you have any online examples to reference?

Regards,
Ryan

When I used the other options of "POL and PHA" I got no response only on "SPI_POL0_PHA0" so I used that one. This is my first time with this accelerometer and SPI in CCS.

I'm using the SPI driver of CCS and datasheets of microcontroller and accelerometer.

Have you tried changing the order of registers read to determine whether you can ever receive something other than 0x33?  It may be a coincidence that this value matches the WHO_AM_I register.  You should also verify your hardware connections to ensure that the VCC, GND, MOSI, MISO, CLK, and CS pins are all connected properly.  It will not be possible to further assist with debugging a third-party sensor without SPI line monitoring.

Regards,
Ryan

I'm using the STEVAL-MKI135V1 board with just the next connections:

• MOSI to SDA
• MISO to SDO
• CLK to CLK
• CS to "Low" "0"
• ADC1, ADC2 and ADC3 to GND
• VDD to 3.3V
• VDD_IO to 3.3V

I got the following response when I was trying to read the CTRL_REG1 in first place (it's the same case with others register).

Step 1: Read "CTRL_REG1"

It only receives 0x33 from the "who am i" register when it is the first register read but when I try another register later the register "who am i" the following responses were obtained:

Step 1: Read "WHO_AM_I"

Step 2: Read "CTRL_REG1"

Hi Tania,

I think what you are seeing after writing the CTRL_REG1 register is normal. If you read the accelerometer x, y, z and you still see 0x33, then there is a problem. Try also communicating with I2C and see if you are getting the same results.

Another issue with ST accelerometer chip is the availability to buy in mass quantities. 

-kel

Hi Ryan,

Thank you for your help.

Regards,

Tania