sd_app_evt_wait() doesn't give microamps consumption

RE: sd_app_evt_wait() doesn't give microamps consumption

Stefan Birnir Sverrisson — Tue, 26 May 2015 07:53:12 GMT

Hi Jarmo

I have updated the current consumption guide, UART section, in order to better address your concerns.

I assume that current consumption is not important for you when you are debugging. Therefore, you can just make a condition to have the UART enabled constantly when debugging.

RE: sd_app_evt_wait() doesn't give microamps consumption

Jarmo — Tue, 26 May 2015 05:13:11 GMT

Thanks for that update! Yes, I know there's leakages in the external circuitry, at some point we have to study the reasons. I looked your guide and it looks good :) However, could you quickly answer how do I need to re-enable UART after getting back from sd_app_evt_wait()? I mean that if I do as follows:

NRF_UART0->TASKS_STOPTX = 1; NRF_UART0->TASKS_STOPRX = 1; NRF_UART0->ENABLE = 0; sd_app_evt_wait(); NRF_UART0->ENABLE = 1;

Is that enough to continue operating with UART, e.g. using your simple_uart_put() example code? Yes, no doubt this is a trivial question and there's comprehensive documentation, but just to save a bit of my time... :)

In my case I want to have debug access from UART (+FTDI/USB) but still want to minimize current consumption, of course.

RE: sd_app_evt_wait() doesn't give microamps consumption

Stefan Birnir Sverrisson — Fri, 22 May 2015 09:41:59 GMT

Hi Jarmo

All peripherals are per default off, and only peripherals that have been explicitly enabled will be on at any time. I have updated the current consumption guide, section "Setup of SPI, UART, TWI interfaces" to more specifically address your concerns.

If you get 48uA in System OFF, that is not normal, that should be ~0.6uA. This leads to that you have leakage current either on a connected GPIO or programming interface. Try to disconnect all external circuits from the nRF51 and disconnect any potentially connected programmer. Have you gone through all the points in the "Troubleshooting" section in the current consumption guide.

RE: sd_app_evt_wait() doesn't give microamps consumption

Jarmo — Thu, 21 May 2015 10:17:12 GMT

Thanks, it looks like UART was using most of the power. Now I can achieve acceptable level :)

Yes, you are right that underscores are the traditional coding style for plain C. I got familiar with those at around 1988. It is really partially matter of what you get used to, but having read different kind of coding styles all these years, I personally favor camelCase. For my eyes, it is just more readable i.e. consumes less brain power... ;-) (I guess the difficulty to distinguish between a space and an underscore causes the incoherence.)

RE: sd_app_evt_wait() doesn't give microamps consumption

RK — Wed, 20 May 2015 13:03:19 GMT

If you read the product spec you'll see that while TX or RX are 'START'ed it needs the HF Clock which consumes lots of power (how much is in the product spec too). Using the simple uart code you'll see if you hunt through it that RX is started when you start the uart but only stopped when the uart deactivate call is called, and what that is depends a bit on which driver you're using. look for the TASKS_STOPRX task being written, that's what disables it again.

And the underscores are a very long-standing C convention. CamelCaseIsForJavaAndObjectiveCProgrammers. It's not modern, it's just different, and I'm sure you'll get very used to reading the underscores after a while.

RE: sd_app_evt_wait() doesn't give microamps consumption

RK — Wed, 20 May 2015 12:53:50 GMT

NRF_TWI->POWER=0
NRF_UART->POWER=0

etc. turns modules entirely off

Of course once they are truly off they aren't going to do anything at all, send out data, send interrupts etc. Usually you don't want to power them off in order to enter app wait() (which is really just __wfe) but you want to power them off when they have finished doing their current task.

RE: sd_app_evt_wait() doesn't give microamps consumption

Jarmo — Wed, 20 May 2015 12:35:37 GMT

It looks like at least UART is causing part of the issue. If I leave away this call: simple_uart_config(RTS_PIN_NUMBER, TX_PIN_NUMBER, CTS_PIN_NUMBER, RX_PIN_NUMBER, false)

The consumption drops to 100 uA and below. But since I need UART, I would like to know how to switch it off before entering sd_app_evt_wait()?

(By the way, those old-fashioned underscores make your code very hard to read because of visual unclarity. Consider switching to modern coding style, like SdApp_evtWait()...)