Confused by power usage changes in firmware

RE: Confused by power usage changes in firmware

mkurtzsd — Tue, 18 Jan 2022 23:08:38 GMT

Hi Simon,

Thank you for this information. It was very helpful. I found the when my peripheral booted up it initialized the time-sync code and turned the radio on which is why it immediately was pulling ~11mA after boot. When the device disconnected, the time-sync mode was turned off which is why the power stayed low after the initial connection. I have modified this behavior to only enable time-sync when needed and the idle power draw is now down around 3.6mA.

Thanks for the clarifications on what/how the time-sync code actually handles the radio power.

-Mike

RE: Confused by power usage changes in firmware

Simonr — Fri, 14 Jan 2022 13:27:28 GMT

Hi again

So I see what's happening here. It took me a moment to understand what the readme actually says, but it describes it correctly.

By default, the examples (both peripheral and central) is in receiver mode by default, and will continuously scan (drawing ~10-11mA). If you press button 1 on the DK, it will switch to transmitter mode and only advertise. The transmitter will begin toggling a GPIO and all 4 onboard LEDs will light up, and the current consumption will go down drastically (to ~2.7mA) as the device will only be advertising and toggling this one GPIO.

However I'm not able to see the current consumption going down as you describe initially. It is either around 10-11mA in receiving mode, or ~2mA in advertising mode. It will also stay the same if I connect to the board with my nRFConnect app for Android. Are you sure you put the device to advertising mode and that it doesn't actually try to scan for other timesync peripherals while it is not connected on your end, as it does indeed advertise while in receiver mode as well by default.

Below are snippets from the Power Profiler application where you can see the two current consumption modes I'm able to replicate with the as-is timesync example project on an nRF52832 DK. You will see some dips in the current consumption in receiving mode, this seems to be because of some timeslots in the application where it sets off some ms to do an advertising event in receiver mode.

Default receiver mode:

Advertising mode:

Best regards,

Simon

RE: Confused by power usage changes in firmware

mkurtzsd — Thu, 13 Jan 2022 15:10:35 GMT

Hi Simon,

My device is the peripheral end connecting to an iPhone and I do control advertising via a button press. When the board first boots and I see the high current, it is not advertising. When I start advertising the current goes up a little less than a mA as expected. Once it connects and begins notifying, the current consumption drops and then never goes back up to initial power on connection levels.

I am powering my board using an Instek PSS-3203 power supply in place of the battery and measuring the current by placing a Keysight 34461A digital multimeter between the power supply and the board. I'll need to investigate if I can output any type of continuous current measurements from the Keysight. I read that a multi-meter is not the best tool to profile the current consumption of the nRF5; but, it is sufficient for my purposes as the change is so dramatic.

A little more detail from some experiments I've done. It appears that when the peripheral is connected and is acting as the time-sync slave, that power is higher until the time-sync master starts sending packets. That is, while the slave is waiting for time-sync packets; it's power draw is 2x what it is once it has received at least one sync packet. If the peripheral is put into time-sync master mode; it's power immediately drops. So, there seems to be an issue with the setup before the time-sync has been established. Perhaps something in the timeslot event handler that changes when a time-sync packet has been received vs. when it hasn't?

Best regards,

-Mike

RE: Confused by power usage changes in firmware

Simonr — Thu, 13 Jan 2022 10:58:47 GMT

Hi again Mike

I'll test this on my end tomorrow (I don't have the right equipment at my home office) and see if I can reproduce and hopefully explain this current consumption better.

Is this the timesync peripheral or central example that you see the high current consumption in? I don't see you mention advertising, scanning or what role the application has specifically. Also, how are you measuring the current consumption? If you're using our PPK or PPK2, can you export and upload the file from the nRFConnect Power Profiler application in a .zip here on DevZone so I can review the current consumption on my end? The looks of it might give an idea of what specifically is drawing this current (although only the radio comes to mind that can draw that amount of current).

Best regards,

Simon

RE: Confused by power usage changes in firmware

mkurtzsd — Wed, 12 Jan 2022 17:14:03 GMT

Hi Simon,

Thank you for the information and the link. I will read Scott's guide and see what I can apply. I'm still a bit baffled about why the current drops so much after the first connection. The power draw is just upon startup initialization until the first connection. After the first disconnect, if I restart advertising, connect, time sync, sample, notify, etc... the current does not rise back up. 🤔

Again, thanks for the investigation starting point.

-Mike

RE: Confused by power usage changes in firmware

Simonr — Wed, 12 Jan 2022 12:42:15 GMT

Hi Mike

This (very high) overall current consumption would be due to the BLE timesync demo not being optimized for power at all I'd imagine. The sd_radio_request() requests a timeslot, which should not increase the power consumption by itself, but the consumption will depend on what is done within the timeslot. This sample seems to request a timeslot that use the radio. Advertising also generally draws more current than a device already in a connection, which explains the drop once you have connected to the device, as it doesn't transmit/receive data as often as if it is advertising constantly.

For example, if the radio is set to transmit continuously it will draw ~11mA (see snippet from the PS below), and so if the advertising interval is low (it advertises very often) there will be few spaces of low current consumption. The post disconnection current of ~4.5mA is likely the CPU running and not much else.

If you need to minimize the current consumption in general in your project, my colleague Scott has made a guide that covers both HW and SW here.

Best regards,

Simon