CC3120: DTIM and LSI influence on power consumption

Hi Lenio,

I found an article that explains the effect on power consumption with different DTIM intervals.  Please take a look at the link below:

Austin,

I understand how the DTIM works. My question is DTIM + LSI. As I originally posted, with an LSI of 300, I expect the CC3120 to wake up every 300ms. If I change DTIM from 1 to 3, I would assume no difference in current consumption, but that is not the case according to the current measurement. That is where I need an explanation.

Thanks.

Hi Lenio,

A few questions about the measurement:

• Which tool is used for the current measurement?
• What is the length of time for the measurement?
• What is the beacon interval with the AP used in this test?  This translates into the DTIM period.
• Also, I'm assuming you have verified LSI is properly configured?
• Have you tried any other DTIM values?

Austin,

I can obtain those details later today after my visit to the customer.

Here is a snapshot of the current consumption. The yellow signal is with a DTIM of 3 and the blue is with a DTIM of 1.  The average current is between the large spikes. 

Can I infer from your questions that this is an unexpected result? In other words, as I would expect, the different DTIM should not affect power consumption? If so, we will dig deeper in the methodology of testing. However if we have a plausible explanation for that difference beyond the test procedure, we will concentrate resources in a different direction. 

Thank you!

Hi Lenio,

Yes, we would expect the power consumption to be about the same between the two trials above. It would be great to dig into the questions asked above for more information.

After visiting the customer, I suspect we have an issue with the LSI configuration. I will try to reproduce it in my setup. Here is the function setting up the LSI:

/******************************************************************************
* Function Name : wifiPlatformSetPowerPolicy
* Description   : sets the power policy
* Arguments     : None
* Return        : wifiPlatformStatus_t
* Pre-requiste  : wifiStart()
* Function type : Global /WiFi platform API
******************************************************************************/
wifiPlatformStatus_t wifiPlatformSetPowerPolicy(void)
{
    int32_t              status = -1;
    wifiPlatformStatus_t returnStatus = WIFI_PLATFORM_STATUS_SUCCESS;
    SlWlanPmPolicyParams_t PmPolicyParams;

    memset(&PmPolicyParams,0,sizeof(SlWlanPmPolicyParams_t));
    PmPolicyParams.MaxSleepTimeMs = WIFI_PLATFORM_WLAN_SLEEP_INTERVAL;
    status = sl_WlanPolicySet(SL_WLAN_POLICY_PM , SL_WLAN_LONG_SLEEP_INTERVAL_POLICY,
                             (_u8*)&PmPolicyParams,sizeof(PmPolicyParams));
    if(status < 0)
    {
        returnStatus = WIFI_PLATFORM_STATUS_SET_MODE_FAILURE;
    }

    return returnStatus;
}

I believe we narrowed the issue down to the inability to make the LSI setting work. I have tried in my setup using the MSP432P401R + CC3120BOOST. I was careful to update CCS to version 7.4, the Wi-Fi plugin to version 1.55.00.42, and the MSP432 SDK to version 1.60.00.12. The example I used is the power_measurement_MSP_EXP432P401R_tirtos_ccs, the TI-RTOS version. I have played with the LSI setting in power_measure.c, line 107:

#define LSI_DURATION_IN_MSEC        (300)

Regardless of the number with which I compile the code, the result is always the same:This is a snapshot of my data acquisition system, which shows an interval of 200ms:

Can you please try the same exercise and let me know if it works?

Thank you!