LSM6DS3 SPI Communication Problem

Sensors IMU & Motion
1

I tried to work with mbed LPC1768 and LSM6DS3-Dev-Board from Sparkfun.

The connections:

uC - LSM6DS3

VOUT 3V3 regulated Out - 3V3

GND-GND

SCLK-SCL

MOSI-SDA (SPI SDI)

MISO-SA0

CS-CS

    #include "mbed.h"
     
    Serial pc(USBTX,USBRX);
    SPI spi(p11, p12, p13); // mosi, miso, sclk
    DigitalOut cs(p14);
     
     
    int main() {
        pc.baud(115200);
        pc.printf("Start");
        spi.format(8,3);
        spi.frequency(100000); 
        // Select the device by seting chip select low
        cs = 1;
        wait(1); 
        
        //Set Register to Default Mode
        //Set SPI to 4 Wire-Mode
        cs = 0;
        spi.write(0x12);
        spi.write(0x04);
        cs = 1;
        wait_ms(1);
        
        uint8_t result;       
        while(1){
            //Select chip
            cs = 0;
            //address
            spi.write(0x8F);
            // send a dummyvalue of 0 to read the first byte returned:
            result = spi.write(0x00);
            //deselect chip
            cs = 1;
            // Send 0x8f, the command to read the WHOAMI register
            printf("WHOAMI register = 0x%X  \n ", result);
             wait_ms(1);
        }
    }

It returned 0x7F every time.

So I checked all bits with the Osziloskop.

Channel 1 - yellow, Channel 2 - blue

Name _

In the zip are all pictures (there are more than 2)…

OSzi.rar (126 KB)

SDA_SDI.jpg
SDA_SDI.jpg1694×1200 148 KB

SCL_SDI.jpg
SCL_SDI.jpg1694×1200 167 KB

2

Hello, and thanks for your post!

Couple of things you might check.

1- The board ships configured for I2c rather than SPI. If you haven’t changed the mode, it’s not going to work. You can enable SPI by opening the address select jumper on the top of the board.the board in SPI.

2- Make sure your any boar you’re using has 3.3 volt I/O. I’m pretty sure the mbed is a 3.3 volt board, but if you test with another controller, it needs to have 3.3 volt logic as well or you risk damaging the board

Also, we don’t support this board under the mbed, you might try using our [hookup guide and code on an Arduino Uno first and then when you have things working, move back over to the mbed.](LSM6DS3 Breakout Hookup Guide - SparkFun Learn)