nRF52832 with MPU9250 using i2c (TWI) on SDK15.2, SD132, Segger Embedded Studio

RE: nRF52832 with MPU9250 using i2c (TWI) on SDK15.2, SD132, Segger Embedded Studio

usmanmehmood55 — Tue, 19 Jan 2021 18:30:13 GMT

I actually did click the verify answer button, but didn't wait for it to actually update before closing the browser. That's my bad.

RE: nRF52832 with MPU9250 using i2c (TWI) on SDK15.2, SD132, Segger Embedded Studio

awneil — Tue, 19 Jan 2021 18:26:20 GMT

RE: nRF52832 with MPU9250 using i2c (TWI) on SDK15.2, SD132, Segger Embedded Studio

haakonsh — Tue, 19 Jan 2021 08:40:18 GMT

Glad to hear, good job! :D

RE: nRF52832 with MPU9250 using i2c (TWI) on SDK15.2, SD132, Segger Embedded Studio

usmanmehmood55 — Tue, 19 Jan 2021 06:36:27 GMT

I managed to make it work. Thank you so much for your help.

RE: nRF52832 with MPU9250 using i2c (TWI) on SDK15.2, SD132, Segger Embedded Studio

awneil — Fri, 15 Jan 2021 14:15:25 GMT

[quote userid="13562" url="~/f/nordic-q-a/70466/nrf52832-with-mpu9250-using-i2c-twi-on-sdk15-2-sd132-segger-embedded-studio/289409#289409"]It's a SW vs HW implementation[/quote]

hence the _sw_ and _hw_ in the file names!

RE: nRF52832 with MPU9250 using i2c (TWI) on SDK15.2, SD132, Segger Embedded Studio

haakonsh — Fri, 15 Jan 2021 12:46:38 GMT

It's a SW vs HW implementation, use the HW one.

RE: nRF52832 with MPU9250 using i2c (TWI) on SDK15.2, SD132, Segger Embedded Studio

usmanmehmood55 — Fri, 15 Jan 2021 11:43:39 GMT

Hi. I'm looking at Nordic's twi_master.h library. And there is something very confusing.

There are two .c fies. One is twi_hw_master.c and other is twi_sw_master.c

Now, each of these files contain their own definitions of the functions twi_master_transfer, and twi_master_init. And the functions are not being overloaded either. They have the same return type, same inputs.
For example, here's twi_master_transfer:
In twi_hw_master.c

bool twi_master_transfer(uint8_t address,
                         uint8_t *data,
                         uint8_t data_length,
                         bool issue_stop_condition)
{
    bool transfer_succeeded = true;

    transfer_succeeded &= twi_master_issue_startcondition();
    transfer_succeeded &= twi_master_clock_byte(address);

    if (address & TWI_READ_BIT)
    {
        /* Transfer direction is from Slave to Master */
        while (data_length-- && transfer_succeeded)
        {
            // To indicate to slave that we've finished transferring last data byte
            // we need to NACK the last transfer.
            if (data_length == 0)
            {
                transfer_succeeded &= twi_master_clock_byte_in(data, (bool)false);
            }
            else
            {
                transfer_succeeded &= twi_master_clock_byte_in(data, (bool)true);
            }
            data++;
        }
    }
    else
    {
        /* Transfer direction is from Master to Slave */
        while (data_length-- && transfer_succeeded)
        {
            transfer_succeeded &= twi_master_clock_byte(*data);
            data++;
        }
    }

    if (issue_stop_condition || !transfer_succeeded)
    {
        transfer_succeeded &= twi_master_issue_stopcondition();
    }

    return transfer_succeeded;
}

And in twi_sw_master.c

bool twi_master_transfer(uint8_t   address,
                         uint8_t * data,
                         uint8_t   data_length,
                         bool      issue_stop_condition)
{
    bool transfer_succeeded = false;
    if (data_length > 0 && twi_master_clear_bus())
    {
        NRF_TWI1->ADDRESS = (address >> 1);

        if ((address & TWI_READ_BIT))
        {
            transfer_succeeded = twi_master_read(data, data_length, issue_stop_condition);
        }
        else
        {
            transfer_succeeded = twi_master_write(data, data_length, issue_stop_condition);
        }
    }
    return transfer_succeeded;
}

This seems very strange to me. Which one is the code supposed to use?

RE: nRF52832 with MPU9250 using i2c (TWI) on SDK15.2, SD132, Segger Embedded Studio

awneil — Thu, 14 Jan 2021 11:28:06 GMT

[quote userid="94615" url="~/f/nordic-q-a/70466/nrf52832-with-mpu9250-using-i2c-twi-on-sdk15-2-sd132-segger-embedded-studio/289150#289150"]I was hesitant to make my own R/W functions,[/quote]

That's just implementing the basic I2C bus access - for these, what Slave you use is irrelevant.

so see the I2C drivers & examples in the SDK

https://infocenter.nordicsemi.com/topic/sdk_nrf5_v17.0.2/twi_scanner_example.html

https://infocenter.nordicsemi.com/topic/sdk_nrf5_v17.0.2/twi_sensor_example.html

https://infocenter.nordicsemi.com/topic/sdk_nrf5_v17.0.2/twi_transaction_mgr_example.html

https://infocenter.nordicsemi.com/topic/sdk_nrf5_v17.0.2/twi_master_with_twis_slave_example.html

RE: nRF52832 with MPU9250 using i2c (TWI) on SDK15.2, SD132, Segger Embedded Studio

usmanmehmood55 — Thu, 14 Jan 2021 11:08:27 GMT

Indeed.

RE: nRF52832 with MPU9250 using i2c (TWI) on SDK15.2, SD132, Segger Embedded Studio

usmanmehmood55 — Thu, 14 Jan 2021 11:08:10 GMT

Hi.

I will try to do that as well.

I was hesitant to make my own R/W functions, but I might have to do it in the end.

Can you please give me a guide/advice on how to do so?

Regards.

RE: nRF52832 with MPU9250 using i2c (TWI) on SDK15.2, SD132, Segger Embedded Studio

haakonsh — Thu, 14 Jan 2021 10:45:54 GMT

I suggest you ask Invensense for their driver and libraries, you should only need to implement the R/W functions with our TWI driver API.

-Edit:

From the invensense website: "Note: The MPU-9250 is marked as EOL and is not recommended for new designs".

https://invensense.tdk.com/products/motion-tracking/9-axis/mpu-9250/

There's also little stock left at distributors.

RE: nRF52832 with MPU9250 using i2c (TWI) on SDK15.2, SD132, Segger Embedded Studio

awneil — Thu, 14 Jan 2021 10:19:54 GMT

[quote userid="94615" url="~/f/nordic-q-a/70466/nrf52832-with-mpu9250-using-i2c-twi-on-sdk15-2-sd132-segger-embedded-studio/289112#289112"]Yes, I did[/quote]

Jolly good.

Amazing how many people don't seem to think of that.

😞

RE: nRF52832 with MPU9250 using i2c (TWI) on SDK15.2, SD132, Segger Embedded Studio

usmanmehmood55 — Thu, 14 Jan 2021 09:54:57 GMT

Yes, I did. But no reply so far. I figured someone here must've done this before, so I asked here as well.

RE: nRF52832 with MPU9250 using i2c (TWI) on SDK15.2, SD132, Segger Embedded Studio

awneil — Thu, 14 Jan 2021 09:53:47 GMT

Have you tried raising a GitHub issue on any of those? Or contacting the authors?

RE: nRF52832 with MPU9250 using i2c (TWI) on SDK15.2, SD132, Segger Embedded Studio

usmanmehmood55 — Thu, 14 Jan 2021 09:42:42 GMT

Hi.

I have tried the following libraries:

https://github.com/Martinsbl/nrf5-mpu-examples

https://github.com/e27182/nRF52832_pesky

https://github.com/simondlevy/MPU

https://github.com/loopj/i2c-hal

None of them compiled. I should correct that in the question, sorry about that.

Thanks for the help. :)

Regards

RE: nRF52832 with MPU9250 using i2c (TWI) on SDK15.2, SD132, Segger Embedded Studio

awneil — Thu, 14 Jan 2021 09:33:06 GMT

[quote userid="94615" url="~/f/nordic-q-a/70466/nrf52832-with-mpu9250-using-i2c-twi-on-sdk15-2-sd132-segger-embedded-studio"]I have found various libraries[/quote]

What libraries, exactly?

Would help if you said what you've tried - so people don't just repeat ones you've already looked at.

[quote userid="94615" url="~/f/nordic-q-a/70466/nrf52832-with-mpu9250-using-i2c-twi-on-sdk15-2-sd132-segger-embedded-studio"]Most of them have compilation errors[/quote]

So what about the one(s) that build OK? What testing / debugging / investigation did you do to find out what's going on and, thus, what's wrong?

Remember that the MPU9250 neither knows nor cares what microcontroller you use - all it sees is the transactions on the I2C bus.

Therefore key to this is being able to check what's happening on the I2C bus - and verify that it's correct, or see where it's going wrong.

So do you have an oscilloscope or analyser to see what's happening on the I2C bus?