LIS3DH SPI 3/4 wire not work properly

[maxim23]

Posted on April 01, 2013 at 16:19

Hello.

I use LIS3DH accelerometer with 4-wire SPI interface.

I attached schematic of accelerometer connection (AccelSch.pdf).

ACL_VDDIO = 3,3 V

ACL_VDD = 3,3 V

Other ACL signals connect to microcontroller pins.

R9A=R9B=R9C=R9D = 100 Ohm.

When I configured accelerometer to work in 4-wire mode I saw that accelerometer send data on SDI pin 6. (SPI_Data_Transfer_4wires_Mode_Img1.jpg and SPI_Data_Transfer_4wires_Mode_Img2.jpg).

Yellow signal - clock (SCL pin 4).

Green signal - SDI pin 6 on net ACL_SDA/SDI/SDIO.

When I configured accelerometer to work in 3-wire mode I saw that amplitude of signal on SDI pin 6 increased (SPI_Data_Transfer_3wires_Mode.jpg).

Why accelerometer send data in 4-wire mode?