Current consumption ble

[lydie]

Hi,

I'm using nrf52832 with s132, so I don't find any information about the current consumed by the device when I'm connected by Bluetooth. I use the driver st7735 and an LCD screen. When my phone is not connected by Bluetooth and my device sleep, the current is 0.43mA. When my phone is not connected, and the LCD screen is ON, the current is around 3.4mA. Until then, everything is normal. But when I'm connected and my device is sleeping, the current is 1.5mA, and if the screen is ON the current is 0.7mA. So I don't understand why the current is increased when I'm connected and when my device is sleeping? And why the current decrease when the screen displays something. On online power profiler, the power consumes when there is a connection but the device is asleep is not indicated, so I don't know if it is normal or not. 

Thanks,

Lydie

[bjorn-spockeli]

Which specific amperemeter? What is the resolution of the amperemter? It needs to have a dynamic range able to accurately measure currents from nA to mA. 

[lydie]

I don't know, it is a multimeter. But I can see the current which decreases when my phone is not connected by Bluetooth so the problem is not the amperemeter. I disabled all timers, so if they are no advertising (on_adv_evt not called), after 10 sec (APP_ADV_DURATION  1000), sleep_enter_mode must be called, but it's not the case. I don't see what type of event can prevent sleep mode from being activated.

[bjorn-spockeli]

What is the brand and model of the muitmeter? Usually a regular multimeters do not have the dynamic range to accurately measure the current consumption of the nRF52 family ICs.  https://devzone.nordicsemi.com/nordic/short-range-guides/b/hardware-and-layout/posts/current-measurement-guide-introduction and https://devzone.nordicsemi.com/nordic/short-range-guides/b/hardware-and-layout/posts/current-measurement-guide-measuring-current-with-p

Note: An ampere-meter will measure average current drawn by the nRF52832 if:

1. The nRF52832 is in a state which draws a constant current, or, the activity on the device changing load current, like BLE connection events, is repeated continuously and has a short cycle time (less than 100ms) so the ampere-meter will average whole load cycles and not parts of the cycle.
2. The dynamic range of the ampere-meter is wide enough to give accurate measurements from a microamp to 15 milliamps.

[lydie]

Fluke 87 Handheld Digital Multimeter, 10A ac 1000V ac 10A dc 1000V dc. But as I said, the mean of measuring the current is not the problem because I can see the current variation when it goes to sleep (system ON) and when it is not connected.

[bjorn-spockeli]

OK, the resolution of the Fluke 87 V is 0,01 µA. The Fluke meter is set to uA when you're measuring the System On current right? I just want to make sure that the measurement HW is accurate enough, otherwise the current measurements can be way off, showing higher average current consumption because either the resolution or sampling rate isnt high enough.  We see a lot of measurements done with HW that is not accurate enough and the average current consumption numbers will then be all over the place. 

lydie said:

But as I said, the mean of measuring the current is not the problem because I can see the current variation when it goes to sleep (system ON) and when it is not connected.

 Are you initializing any peripherals when you get the connected event? Are you advertising when you're not connected? If so which advertisment interval? If you're expecting the nRF to sleep in between the advertising events, then you can toggle a GPIO after calling idle_state_handle(). If the nRF is only waking up from the advertisment events, then you should see the GPIO toggle at the same interval. 

If it toggles at a higher interval, then I would start putting log statements or toggeling GPIOs in event handlers to figure which event thats waking up the nRF. 

Best regards

Bjørn