Hello,
I am working on a custom PCB with a nRF52832 and I've been unable to get the ON IDLE power under 480uA. Here are the basics regarding the setup
- nRF52832 Rev 1
- SDK 12.1.0
- Soft Device 132, revision 3.0.0
- FreeRTOS port from SDK w/ a few customizations
- NOTE! We are using tickless idle in FreeRTOS -- added by edit on Mar-17-2017
- Using TWI1, UART0, GPIO with port events, and a COMP peripheral
- All 3 RTCs in use (RTC0 for Soft Device, RTC1 for FreeRTOS, and RTC2 for "alarm timers").
- 32kHz Crystal Oscillator, 20 PPM accuracy
- 32MHz Crystal Oscillator
- DCDC converter is enabled due to HW design
- Using SAADC to make a battery level measurement
Other than the use of RTC2, the DCDC converter, and the COMP peripheral this is a very similar setup to a nRF51 project we did previously and was very low power. I am suspicious that I have done something wrong setting up the clocks as my most likely cause of the extra power burn. I'll describe the basic scenario below.
What I have found is that as the system is coming up the 32kHz OSC is first turned on (using the CLOCK driver), for our BSP to drive a 1 second heartbeat "alarm". It then is enabled again as FreeRTOS is brought up to drive the OS timer system. Lastly we enable the soft device through the call to sd_softdevice_enable(); in softdevice_handler_init();. It is immediately after that call that the ON IDLE power jumps from ~50uA to ~500uA and stays that high. Even the 50uA is too high for us, but I'm focused on the bigger issue here first.
I've been through the data sheet, the errata, the nRF51 -> nRF52 migration guide, and the forum and so far have had no luck reducing or even identifying my power culprit. I've implemented the work around for PAN-89 even though we don't use EASYDMA on the TWI. I've stepped through every peripheral to make sure only the ones I want are on. I've verified that the LF and HF clocks appear to be starting and the external HF clock is being used. The device is advertising, connectable and performs all of the other operations expected of it.
My next step is to neuter our app and FreeRTOS on our board and see if just bringing up the Soft Device by itself with a simple blinky style application results in the same power burn. In the mean time I was hoping if anyone had any ideas if they could respond to this post. I'm particularly interested in why the power consumption jumps when the Soft Device is enabled.
The nRF51 documentation used to have a very nice couple of tables of peripherals, the clocks they needed and the resulting power consumption. That would be very useful for the nRF52. It is possible I've missed it.
Thanks, John
