Nexys A7, Accelerometer, and Microblaze

[aadgl]

I have the onboard accelerometer working from VHDL, but not from microblaze with AXI Quad SPI.
> It always reads a value of 0x00, for the given settings I think it should return 0xAD
> I have tested in 2019.2 and 2021.2, same results.
> I have tried many settings for the "options" parameter:
   Status = XSpi_SetOptions(SpiInstancePtr, options);

I am thinking something is misconfigured.

Any clues or a working example would be greatly appreciated.

Thanks,
Dave

Below is the test code that was adapted from first comment:

-----

// https://chanon-khong.medium.com/zynq-reading-analog-value-from-adc-ltc2314-with-axi-quad-spi-11be59b6d693

/***************************** Include Files *********************************/
#include <stdio.h>
#include "platform.h"
#include "xil_printf.h"
#include "xparameters.h"    /* XPAR parameters */
#include "xspi.h"
#include "sleep.h"

#define SPI_DEVICE_ID        XPAR_AXI_QUAD_SPI_0_DEVICE_ID
int SpiPolledExample(XSpi *SpiInstancePtr, u16 SpiDeviceId);
static XSpi  SpiInstance;     /* The instance of the SPI device */

int main(void)
{
    init_platform();
    int Status;

    print("\r\nHello World\n\r");

    Status = SpiPolledExample(&SpiInstance, SPI_DEVICE_ID);
    if (Status != XST_SUCCESS) {
        return XST_FAILURE;
    }

    cleanup_platform();
    return 0;
}

int SpiPolledExample(XSpi *SpiInstancePtr, u16 SpiDeviceId)
{
    int Status;

    XSpi_Config *ConfigPtr;    /* Pointer to Configuration data */

    ConfigPtr = XSpi_LookupConfig(SpiDeviceId);
    if (ConfigPtr == NULL) {
        return XST_DEVICE_NOT_FOUND;
    }

    Status = XSpi_CfgInitialize(SpiInstancePtr, ConfigPtr,
                  ConfigPtr->BaseAddress);
    if (Status != XST_SUCCESS) {
        return XST_FAILURE;
    }

    u32 options = XSP_MASTER_OPTION | XSP_MANUAL_SSELECT_OPTION;
    //u32 options = (XSP_MASTER_OPTION | XSP_CLK_ACTIVE_LOW_OPTION ) | XSP_MANUAL_SSELECT_OPTION;
    Status = XSpi_SetOptions(SpiInstancePtr, options);
    if (Status != XST_SUCCESS) {
        return XST_FAILURE;
    }

    XSpi_Start(SpiInstancePtr);
    XSpi_IntrGlobalDisable(SpiInstancePtr);
    XSpi_SetSlaveSelect(SpiInstancePtr, 0x01);

    unsigned int *spibase = (unsigned int *)0x44A00000U;
    unsigned int *spicr = spibase+0x60/4;
    unsigned int d0 = *spicr;
    xil_printf("spicr = 0x%08X -> 0x%08X\r\n",spicr,d0);

    u8  WriteByte1=0x0B;    // instr = 0x0B => read accel
    u8  WriteByte2=0x00;    // addr  = 0x00 => read 0xAD
    u8  WriteByte3=0x00;    // addr  = 0x00 => dummy
    u8  ReadByte1=0xFF;
    u8  ReadByte2=0xFF;
    u8  ReadByte3=0xFF;

    for(int i=0;i<3;i++)
      {
        Status = XSpi_Transfer(SpiInstancePtr, &WriteByte1, &ReadByte1, 1);
        if (Status != XST_SUCCESS) {
            return XST_FAILURE;
        }
        XSpi_Transfer(SpiInstancePtr, &WriteByte2, &ReadByte2, 1);
        if (Status != XST_SUCCESS) {
            return XST_FAILURE;
        }
        XSpi_Transfer(SpiInstancePtr, &WriteByte3, &ReadByte3, 1);
        if (Status != XST_SUCCESS) {
            return XST_FAILURE;
        }
        xil_printf("0x%02X -> 0x%02X%    0x%02X -> 0x%02X%    0x%02X -> 0x%02X\r\n",
                WriteByte1,ReadByte1, WriteByte2,ReadByte2, WriteByte3,ReadByte3);
    }
    return XST_SUCCESS;
}

 

[aadgl]

By originator, minor change, no effect:

    for(int i=0;i<3;i++)
      {
        Status = XSpi_Transfer(SpiInstancePtr, &WriteByte1, &ReadByte1, 1);
        if (Status != XST_SUCCESS) {
            return XST_FAILURE;
        }
        Status = XSpi_Transfer(SpiInstancePtr, &WriteByte2, &ReadByte2, 1);
        if (Status != XST_SUCCESS) {
            return XST_FAILURE;
        }
        Status = XSpi_Transfer(SpiInstancePtr, &WriteByte3, &ReadByte3, 1);
        if (Status != XST_SUCCESS) {
            return XST_FAILURE;
        }
        xil_printf("0x%02X -> 0x%02X%    0x%02X -> 0x%02X%    0x%02X -> 0x%02X\r\n",
                WriteByte1,ReadByte1, WriteByte2,ReadByte2, WriteByte3,ReadByte3);
    }

[JColvin]

HI @aadgl,

What SPI clock frequency are you providing the AXI Quad SPI IP / what frequency ratio are you using in the IP itself? As per the ADXL362 datasheet in the Serial Communications section ( https://www.analog.com/media/en/technical-documentation/data-sheets/adxl362.pdf, pg 19) you will end up needing a fairly slow clock ranging between 1 MHz and 8 MHz.

Thanks,
JColvin

 

[aadgl]

Hi JColvin,

Good question!

External clock is 100 MHz
From above, I think the Frequency Divider is 16x2=32
The SPI clock would be:  100MHz/32 = 3.125MHz

I was using 16x16 and rebuilt with the above settings, no change in results.

Thanks,
Dave

Edited April 19, 2022 by aadgl