i2c_transfer() reads all zeros

RE: i2c_transfer() reads all zeros

Learner — Thu, 04 Nov 2021 17:06:19 GMT

Hi Simon,

Have you had a chance to look at the FIFO EMPTY bit always set problem I reported last week?

Kind regards

Mohamed

RE: i2c_transfer() reads all zeros

Learner — Fri, 29 Oct 2021 13:56:26 GMT

Good Afternoon Simon,

I just had this thought, correct me if I am wrong.

I thought the reason the EMPTY bit in the FIFO register FIFO_SRC_REG is always set is because STREAM mode does not use the FIFO. Instead I must use the status register STATUS_REG (27h) and poll one of the data ready bits e.g. ZYXDA. This works but I really must use the FIFO in the following way:

1- Only Read sensor data if FIFO is not EMPTY

2- Read FSS bits [0:4] to determine the number of samples stored in the FIFO

3- Read the data from the FIFO

Unfortunately, I cannot get past step 1 because EMPTY bit is always zero. Note, I cannot use INT1/2 interrupts, so I am polling the EMPTY bit instead.

Please check this with your design team.

Kind regards

Mohamed

RE: i2c_transfer() reads all zeros

Simon — Fri, 29 Oct 2021 13:46:50 GMT

I don't have any knowledge about the LIS2DE12, so I'm not sure why this happens:

[quote user="Learner"]Any update on my question about why I am always getting FIFO EMPTY bit set when I read the FIFO status register LIS2DE12_FIFO_SRC_REG?[/quote]

Maybe a logic trace would be useful, to figure out if the issue is on the Nordic side or the LIS2DE12

I will take a deep dive into the LIS2DE12 datasheet on Monday and see if I can get to the bottom of it.

RE: i2c_transfer() reads all zeros

Simon — Thu, 28 Oct 2021 11:22:55 GMT

I'll take a look at it👍

RE: i2c_transfer() reads all zeros

Learner — Thu, 28 Oct 2021 10:43:21 GMT

Hi Simon,

Any update on my question about why I am always getting FIFO EMPTY bit set when I read the FIFO status register LIS2DE12_FIFO_SRC_REG?

See the notes I added to this ticket yesterday.

Thank you

Kind regards

Mohamed

RE: i2c_transfer() reads all zeros

Learner — Tue, 26 Oct 2021 16:30:49 GMT

Good Morning Simon,

Thank you for sharing the link about i2c_burst_read().

I did not have to use the logic analyser because when I disabled the sensor internal filter (cleared FDS bit) I could read the sensor data.

lis2de12_writeb( LIS2DE12_CTRL_REG2,0xB8 );

changed to

lis2de12_writeb( LIS2DE12_CTRL_REG2,0x80 );

However, I still cannot read the content of the FIFO. I tried both FIFO and stream modes and neither worked. When in stream mode the FIFO seemed to always be empty (EMPTY bit always set).

I have not had a chance to try the i2c_burst_read() but I will do tomorrow.

------------------

Updated post

------------------

I have now tried to read the fifo using i2c_burst_read() but I am still finding that when I read register LIS2DE12_FIFO_SRC_REG (address 0x2F) I get 0x20 meaning the fifo is always empty. I am enabling fifo (FIFO_EN) and selecting stream mode by writing 0x80 to register LIS2DE12_FIFO_CTRL_REG.

Below is the code used to read the content of the fifo.

static int32_t lis2de12_read_fifo(uint8_t add, uint8_t *data)
{
    return i2c_burst_read( accelerometer.handle,    // i - Pointer to the device structure for an I2C controller
                           LIS2DE12_I2C_ADD,        // i - Address of the I2C device to read from
                           add,                     // i - Internal address from which the data is read
                           data,                    // o - Buffer to read the data into
                           6                    );  // i - Number of bytes to read
}


boolean_t lis2de12_getxyz_fifo(void)
{
    boolean_t   result = false;
    uint8_t     fifo_status;
    uint8_t     d[6],i;
    union {
            uint8_t  b[2];
            int16_t  i;
    } iandb;

    accelerometer.vector = accelerometer.oldvector;

    if (accelerometer.present)
    {
        lis2de12_readb( LIS2DE12_FIFO_SRC_REG, &fifo_status );
        if ( fifo_status & 0x1f )
        {
            if ( lis2de12_read_fifo( LIS2DE12_FIFO_READ_START | 0x80, d ) == 0 )
            {
                iandb.b[1] = d[0];
                iandb.b[0] = d[1];
                accelerometer.x = iandb.i;

                iandb.b[1] = d[2];
                iandb.b[0] = d[3];
                accelerometer.y = iandb.i;

                iandb.b[1] = d[4];
                iandb.b[0] = d[5];
                accelerometer.z = iandb.i;

                accelerometer.vector = (uint32_t)accelerometer.x * (uint32_t)accelerometer.x +
                                       (uint32_t)accelerometer.y * (uint32_t)accelerometer.y +
                                       (uint32_t)accelerometer.z * (uint32_t)accelerometer.z;
                printf( "[%u s] ", timer_GetOneSecondTime() ); //DBG
                printf( "STATUS_REG = 0x%02x acc_x = 0x%04x acc_y = 0x%04x acc_z = 0x%04x v = %d acc_oldv = %d\n",
                        fifo_status,
                        accelerometer.x, accelerometer.y, accelerometer.z,
                        accelerometer.vector,
                        accelerometer.oldvector                             );
                
                result = true;
            }
        }
    }

    return result;

}//lis2de12_getxyz_fifo()

-----------------------

If I don't bother to read and check the content of the FIFO source register (LIS2DE12_FIFO_SRC_REG) for the existence of data before reading then I can read the sensor data successfully. The two commented out lines are shown below.

//      lis2de12_readb( LIS2DE12_FIFO_SRC_REG, &fifo_status );
//      if ( fifo_status & 0x1f )

The data read is shown below, ignore the STATUS_REG values because it is not being read.

[16 s] STATUS_REG = 0x05 acc_x = 0x00fd acc_y = 0x00ff acc_z = 0x0042 v = 133390 acc_oldv = 133390
[17 s] STATUS_REG = 0x00 acc_x = 0x00fd acc_y = 0x00ff acc_z = 0x0042 v = 133390 acc_oldv = 133390

[18 s] STATUS_REG = 0x00 acc_x = 0x00f5 acc_y = 0x0006 acc_z = 0x00c5 v = 98870 acc_oldv = 133390
[19 s] STATUS_REG = 0x00 acc_x = 0x00f9 acc_y = 0x00f8 acc_z = 0x0042 v = 127861 acc_oldv = 98870
[20 s] STATUS_REG = 0x00 acc_x = 0x00bf acc_y = 0x00f2 acc_z = 0x00fa v = 157545 acc_oldv = 127861
[21 s] STATUS_REG = 0x00 acc_x = 0x00c1 acc_y = 0x00f3 acc_z = 0x00f9 v = 158299 acc_oldv = 157545
[22 s] STATUS_REG = 0x05 acc_x = 0x0006 acc_y = 0x00bc acc_z = 0x0006 v = 35416 acc_oldv = 158299
[23 s] STATUS_REG = 0x00 acc_x = 0x000a acc_y = 0x00bc acc_z = 0x0000 v = 35444 acc_oldv = 35416
[24 s] STATUS_REG = 0x00 acc_x = 0x000e acc_y = 0x00bd acc_z = 0x0002 v = 35921 acc_oldv = 35444
[25 s] STATUS_REG = 0x00 acc_x = 0x0010 acc_y = 0x00be acc_z = 0x0001 v = 36357 acc_oldv = 35921
[26 s] STATUS_REG = 0x05 acc_x = 0x00ff acc_y = 0x0040 acc_z = 0x00fd v = 133130 acc_oldv = 36357
[27 s] STATUS_REG = 0x00 acc_x = 0x0003 acc_y = 0x0040 acc_z = 0x0003 v = 4114 acc_oldv = 133130
[28 s] STATUS_REG = 0x00 acc_x = 0x0002 acc_y = 0x00bc acc_z = 0x0008 v = 35412 acc_oldv = 4114
[29 s] STATUS_REG = 0x00 acc_x = 0x0000 acc_y = 0x00bc acc_z = 0x000b v = 35465 acc_oldv = 35412
[30 s] STATUS_REG = 0x05 acc_x = 0x0000 acc_y = 0x00bc acc_z = 0x000b v = 35465 acc_oldv = 35465
[30 s] STATUS_REG = 0x00 acc_x = 0x0001 acc_y = 0x00bd acc_z = 0x000b v = 35843 acc_oldv = 35465
[31 s] STATUS_REG = 0x05 acc_x = 0x00fa acc_y = 0x0001 acc_z = 0x003f v = 66470 acc_oldv = 35843
[32 s] STATUS_REG = 0x00 acc_x = 0x00fa acc_y = 0x0000 acc_z = 0x0041 v = 66725 acc_oldv = 66470

Kind regards

Mohamed

RE: i2c_transfer() reads all zeros

Simon — Mon, 25 Oct 2021 22:30:26 GMT

Hey, did you capture a trace?

I'll take a closer look at this tomorrow.

What happens if you try to read the data in the same way it's done in the lis2ds12 driver, by using i2c_burst_read()?

https://github.com/nrfconnect/sdk-zephyr/blob/v2.6.99-ncs1/drivers/sensor/lis2ds12/lis2ds12_i2c.c#L28-L29

RE: i2c_transfer() reads all zeros

Learner — Fri, 22 Oct 2021 15:17:40 GMT

Thank you Simon.

I tried your suggestion to make the struct declaration static but it did not make any difference.

Hooking up a logic analyser to SDA and SCL lines was going to be my next move but I was hoping you may be able to find what could be wrong in my code without resorting to a logic analyser. I am not suspecting the hardware, are you?

The reason I am saying this is because I can read the control and status registers content without any problem. If there was something wrong with the hardware setup it would have affected them too.

Anyway, I am working from home today and the logic analyser is in the office. So, I will do it on Monday and will give you some feedback.

Kind regards

Mohamed

RE: i2c_transfer() reads all zeros

Simon — Fri, 22 Oct 2021 13:13:13 GMT

Try setting struct i2c_msg msgs[2] to static, like shown below:

static int32_t lis2de12_read_fifo(uint8_t add, uint8_t *b)
{
    static struct i2c_msg msgs[2];

    /* Send the address to read from */
    msgs[0].buf = &add;
    msgs[0].len = 1U;
    .
    .

Do you have a logic analyzer? That is quite useful to see what's actually going on, on the lines. If you have one, could you you attach it to the SDA and SCL lines and upload the trace here?

Best regards,

Simon

RE: i2c_transfer() reads all zeros

Learner — Fri, 22 Oct 2021 08:58:55 GMT

Thank you Simon.

I am looking forward to read your findings.

Kind regards

Mohamed

RE: i2c_transfer() reads all zeros

Simon — Thu, 21 Oct 2021 23:12:46 GMT

Hello,

I'll take a look at this tomorrow.

Best regards,

Simon