I2C clock stop issue

RE: I2C clock stop issue

Jithin A — Tue, 04 Apr 2023 10:51:23 GMT

Thank you Kenneth for the reference.

I now find the issue and fixed it.

The issue is with the STOP task.

Earlier I was only waiting for the write/read task to complete and not stopping the TWIM which is still running. Now after reading the TWIM operation carefully I noticed I need to call STOP task to STOP the TWIM operation which I was not doing on my end.

Below is the fixed code

void
twim_write (const uint8_t *p_buf, size_t len)
{
    //
    // Stop previous session if any
    //
	nrf_twim_task_trigger(NRF_TWIM1, NRF_TWIM_TASK_STOP);

    //
    // Prepare for the new session
    //
	nrf_twim_tx_buffer_set(NRF_TWIM1, p_buf, len);
    nrf_twim_rx_buffer_set(NRF_TWIM1, NULL, 0);
	nrf_twim_address_set(NRF_TWIM1, DEV_I2C_ADDR);

    //
    // Start tx task
    //
	nrf_twim_task_trigger(NRF_TWIM1, NRF_TWIM_TASK_STARTTX);

    //
    // Wait until the transmission is complete, clear the event on complete
    //
	while(!nrf_twim_event_check(NRF_TWIM1, NRF_TWIM_EVENT_LASTTX));
	nrf_twim_event_clear(NRF_TWIM1, NRF_TWIM_EVENT_LASTTX);

    //
    // Write task is complete, STOP the session
    //
	nrf_twim_task_trigger(NRF_TWIM1, NRF_TWIM_TASK_STOP);
}

void
twim_read (uint8_t *p_buf, size_t len)
{
    //
    // Stop previous session if any
    //
	nrf_twim_task_trigger(NRF_TWIM1, NRF_TWIM_TASK_STOP);

    //
    // Prepare for the new session
    //
	nrf_twim_tx_buffer_set(NRF_TWIM1, NULL, 0);
    nrf_twim_rx_buffer_set(NRF_TWIM1, p_buf, len);
	nrf_twim_address_set(NRF_TWIM1, DEV_I2C_ADDR);

    //
    // Start rx task
    //
	nrf_twim_task_trigger(NRF_TWIM1, NRF_TWIM_TASK_STARTRX);

    //
    // Wait until the reception is complete, clear the event on complete
    //
	while(!nrf_twim_event_check(NRF_TWIM1, NRF_TWIM_EVENT_LASTRX));
	nrf_twim_event_clear(NRF_TWIM1, NRF_TWIM_EVENT_LASTRX);

    //
    // Read task is complete, STOP the session
    //
	nrf_twim_task_trigger(NRF_TWIM1, NRF_TWIM_TASK_STOP);
}

RE: I2C clock stop issue

Kenneth — Tue, 04 Apr 2023 09:25:20 GMT

Hello,

I suggest to look at the datasheet on the TWIM peripheral:
https://infocenter.nordicsemi.com/topic/ps_nrf5340/twim.html

There are several figures there that may be helpful.

Kenneth

RE: I2C clock stop issue

Jithin A — Tue, 04 Apr 2023 07:46:46 GMT

Hi, sorry for the delayed response.

I was working on another high priority task for which I could not see to this taks.

Let me explain my findings:

I see I can not use Zephyr RTOS in secure (TF-M) application image and this force me to use nrf lib for TWI(I2C) implementation.

I did not find any suitable example for implementing I2C in secure (TF-M) application image.

After doing some R&D on I2C I ended up with the above implementation which uses nrf lib for TWI using DMA.

I see clock on SCL even after I get NRF_TWIM_EVENT_LASTRX event.

I'll be active for this case from now as all my high priority tasks are complete.

Please guide me to any available example or correct me if I am doing anything wrong.

Thank you in advance.

RE: I2C clock stop issue

Kenneth — Tue, 28 Feb 2023 13:04:56 GMT

Hello,

I am not entirely sure what is failing here, you are working very low level.

First of all make sure you have read the TWIM chapter:
https://infocenter.nordicsemi.com/topic/ps_nrf5340/twim.html

Secondly I suggest to try to use the i2c_nrfx_twim_transfer()->twim_xfer() to setup and execute transfer, instead of the manual setup of buffers, events and tasks. If you still want to handle buffers, events and tasks manually, then look at the implementation of i2c_nrfx_twim_transfer().

What is the state of the SDA line here when SCL is low?

Best regards,
Kenenth

RE: I2C clock stop issue

Jithin A — Tue, 28 Feb 2023 02:24:48 GMT

Thank you, please let me know ASAP

RE: I2C clock stop issue

Kazi Afroza Sultana — Mon, 27 Feb 2023 18:52:40 GMT

Hello,

I am looking into few issues regarding this. I will reply you tomorrow.

Regards,

Kazi

RE: I2C clock stop issue

Jithin A — Mon, 27 Feb 2023 09:43:25 GMT

Hi,

Anyone please help me with this.