nRF5340 Tickless Idle

[jvr]

Hi

I'm currently evaluating the possibility of using nRF5340 in an upcoming project. As the chip is very new it's easy to understand that all specifications are not yet available. What I'm interested is the current / power consumption in tickless sleep. I would like to measure that using nRF5340-PDK (which I already have). I would need to have resolution of about 1 ms (1/1024 is fine).

I (eventually) did manage to get Zephyr toolchain and Segger Embedded Studio installed on Windows as per instructions, but couldn't figure out how to enable tickless idle. I could only reach current consumption of 1.65 mA (measured from P22, powered with coin cell, as instructed in the ). Curiously the current consumption doesn't seem to be at all by LED duty cycle or sleep time, nor 'nrf only' switch. I've been working on the 'blinky' example.

Is tickless idle supported yet?

Would you happen to have some sample project that I could try? I'm sure you have tested this many times already.

Thanks
Juho

[jvr]

One hunch would be that the network core is still active. I think the Blinky example itself could perhaps be updated to blink two LEDs, one by each core. I couldn't figure out how to achieve that yet.

[Håkon Alseth]

Hi,

 

This is what I did.

1. issue a recover to ensure clean state: "nrfjprog --recover -f nrf53"

2. take the samples/basic/blinky/ and configure it with board name "nrf5340_dk_nrf5340_cpuapp", and flash that.

3. Power cycle

4. Measure with an am-meter over P22. (I measure ~13-14 uA)

I kept the USB powered and connected. There's several buffers etc. that are not on the VDD_NRF net, including the GPIOs, so if you do not keep the VBUS present, it might leak into those connected nets, and your current consumption will then be higher than expected.

Could you try this and see if you measure in the uA range?

 

Kind regards,

Håkon

[jvr]

Hi

Thank you for the quick reply.

I actually have two PDKs and decided to try both, running recovery and flash for each.. Surprisingly enough, the original kit yields 1.70 mA in P22 while the other shows consumption close to zero (need to rerun the test with a better multimeter). The boards appear identical and have the same modifications made (=cut the solder bridges between P22 and P23 terminals). Switches are in the same position. Only difference I could see in the boards was in the number in bottom layer silk screen (top left corner): the PDK showing 1.70 mA has 44-19-946 while the other board has 44-19-969. Is that a serial number or batch? Could it be that the other PDK is defective?

Having USB connected didn't seem to make much of a difference. Actually your tip is a contradicting the instruction in Info Center (https://infocenter.nordicsemi.com/index.jsp?topic=%2Fug_nrf52832_dk%2FUG%2Fnrf52_DK%2Fhw_meas_current.html), although I do see your point.

Thanks
Juho

[Håkon Alseth]

Hi Juho,

  

jvr said:

I actually have two PDKs and decided to try both, running recovery and flash for each.. Surprisingly enough, the original kit yields 1.70 mA in P22 while the other shows consumption close to zero (need to rerun the test with a better multimeter). The boards appear identical and have the same modifications made (=cut the solder bridges between P22 and P23 terminals). Switches are in the same position. Only difference I could see in the boards was in the number in bottom layer silk screen (top left corner): the PDK showing 1.70 mA has 44-19-946 while the other board has 44-19-969. Is that a serial number or batch? Could it be that the other PDK is defective?

I do not think there's something wrong with your nRF53 device. This is a PDK, so my initial thoughts is that this might be something external to the nRF (leakage in the PDK itself for instance).

Mine showed ~3 mA until I issued a nrfjprog --recover, which could have been the network core CPU, but I cannot state that for certain.

Note, you should have the USB attached, even when using a coin-cell or any other external power:

https://infocenter.nordicsemi.com/topic/ug_nrf5340_pdk/UG/nrf5340_PDK/hw_measure_current.html?cp=3_0_3_5

 

Does the 1.7 mA kit behave equally if powered via USB vs. via coin-cell?

In any case; I'll report these findings to the PDK hardware team, so that they can look into this. 

 

Kind regards,

Håkon

[jvr]

Hi

1.7 mA kit behaves very similarly with USB vs coin cell. There's perhaps 50 µA of difference.

It seems odd that "nRF ONLY" switch doesn't seem to make any difference either.

Maybe I'll try to isolate the nRF even some more.

I ran the recovery & download process a few times, the output was identical for each board.

1.70 mA board does take about 4 mA for a few seconds after startup before it drops to 1.70.

Working board drops to 16.5 µA or so almost instantly.

Thanks
Juho