nRF5 action!

Uhrheber

So, you want to shut the CPU down, leaving only RTC and PPI running, and generate a wakeup event every 100ms, did I get that right?
I didn't dig that far into the datasheet, and also I don't have any board for testing (yet).

Also, I didn't check whether the debugger will survive a power down/up cycle.
Does it?

NeverDie

@Uhrheber said in nRF5 Bluetooth action!:

So, you want to shut the CPU down, leaving only RTC and PPI running, and generate a wakeup event every 100ms, did I get that right?

Yes. I hope to do more than only just that using the PPI while the CPU sleeps, but that does seem like the first step.

NeverDie

@Uhrheber said in nRF5 Bluetooth action!:

Also, I didn't check whether the debugger will survive a power down/up cycle.
Does it?

Don't know. I haven't started using the debugger yet.

Uhrheber

In this example from Nordic, they're using the RTC's compare interrupt:
http://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.nrf52%2Fdita%2Fnrf52%2Fapp_example%2Fsolar_beacon%2Fintroduction.html

Average current consumption is 19µA, including sensor reading, data transmission and Bluetooth advertizing.
Not too bad, I'd say.

NeverDie

@Uhrheber said in nRF5 Bluetooth action!:

In this example from Nordic, they're using the RTC's compare interrupt:

Yeah, but that part of it is running on the MCU, not the PPI.

void RTC0_IRQHandler(void)
{
    NRF_RTC0->EVTENCLR = (RTC_EVTENCLR_COMPARE0_Enabled << RTC_EVTENCLR_COMPARE0_Pos);
    NRF_RTC0->INTENCLR = (RTC_INTENCLR_COMPARE0_Enabled << RTC_INTENCLR_COMPARE0_Pos);
    NRF_RTC0->EVENTS_COMPARE[0] = 0;
    
    m_rtc_isr_called = true;    
}

NeverDie

~~Anyhow, I don't see a way to do an RFM69 style "listen mode" using just the PPI on the nRF52832. I think this may be a dead end.~~

NeverDie

Looks as though there is EVTEN, which on the RTC needs to be enabled to get the PPI to work. Shown in Figure 46.

NeverDie

Bingo! Added this, and it now works:

  NRF_RTC0->EVTENSET=1;  //enable routing of RTC events to PPI.

:)

NeverDie

More good news. As far as the PPI is concerned, an event such as OVRFLW is still just as active as if it had been cleared, even if it hasn't. Here's the proof:

  NRF_RTC0->TASKS_TRIGOVRFLW=1;

  NRF_PPI->CH[0].EEP = (uint32_t)&NRF_RTC0->EVENTS_OVRFLW;  //when RTC overflow occurs.
  NRF_PPI->CH[0].TEP = (uint32_t)&NRF_RTC0->TASKS_TRIGOVRFLW;  //set COUNTER to be near another overflow.
  NRF_PPI->CHENSET=1; //enable Channel 0.
  NRF_RTC0->EVTENSET=B10;  //enable routing of RTC OVRFLW events to PPI.

functions as follows:
https://pastebin.com/Z09e7tMK

d00616

@NeverDie said in nRF5 Bluetooth action!:

~~Anyhow, I don't see a way to do an RFM69 style "listen mode" using just the PPI on the nRF52832. I think this may be a dead end.~~

It looks like you are implementing a new radio protocol and you are coming forward.

What do you think about forking the MY_RADIO_NRF5_ESB into a new one? The nRF5 code is designed to implement additional protocols for nRF5.

If you remove the address reverse code, there are no OTA conflicts with the ESB protocol. The address width can be enhanced by 2 bits to allow better AES encryption and lager packages.

NeverDie

@d00616 said in nRF5 Bluetooth action!:

It looks like you are implementing a new radio protocol and you are coming forward.

Yes, I'm presently focused on trying to reduce the amount of energy consumed by probably the hardest case of all: a battery/solar/supercap receiver that needs to be both highly responsive (within 100ms) and listening 24/7 without running out of juice. Of course, one can always throw bigger batteries or bigger solar panels at the problem, but I'm first trying to be as ultra efficient as possible so that won't be necessary. The benefit will be smaller size, not to mention lower cost.

I am posting my findings as I go because there is precious little in the way of working examples, so I may yet still be of help to others in that way. From the view count, it does seem that people are reading this thread, even if not many are posting.

d00616

@NeverDie said in nRF5 Bluetooth action!:

I am posting my findings as I go because there is precious little in the way of working examples, so I may yet still be of help to others in that way. From the view count, it does seem that people are reading this thread, even if not many are posting.

btw. Thank you for sharing you knowledge here. In my option this is very helpful for me.

NeverDie

@d00616

I think you'll find this interesting:

  NRF_RADIO->TASKS_DISABLE=1;  //sleep the radio
  while (NRF_RADIO->STATE) {}; //wait until radio is DISABLED (i.e. STATE=0);

  NRF_RTC0->TASKS_TRIGOVRFLW=1;  //set COUNTER to trigger an overflow after 16 TICKS.

  NRF_PPI->CH[0].EEP = (uint32_t)&NRF_RTC0->EVENTS_OVRFLW;  //when RTC overflow occurs.
  NRF_PPI->CH[0].TEP = (uint32_t)&NRF_RTC0->TASKS_TRIGOVRFLW;  //set COUNTER to be near another overflow.
  NRF_PPI->FORK[0].TEP = (uint32_t)&NRF_RADIO->TASKS_RXEN;  //turn on the radio receiver
  NRF_RTC0->EVTENSET=B10;  //enable routing of RTC OVRFLW events to PPI.

  //When Radio state TXIDLE is reached, perform an RSSI sample.  There is no shortcut for this, so we must use PPI.
  NRF_PPI->CH[1].EEP = (uint32_t)&NRF_RADIO->EVENTS_READY;  //After event READY, radio shall be in state TXIDLE.
  NRF_PPI->CH[1].TEP = (uint32_t)&NRF_RADIO->TASKS_RSSISTART; //Take the RSSI sample

  NRF_PPI->CH[2].EEP = (uint32_t)&NRF_RADIO->EVENTS_RSSIEND;  //After event RSSIEND, RSSI measurement is finished and radio will be in state TXIDLE.
  NRF_PPI->CH[2].TEP = (uint32_t)&NRF_RADIO->TASKS_DISABLE; //Sleep the radio
  NRF_PPI->CHENSET=B111; //enable Channel 2, Channel 1 and Channel 0.
  sleep(1000000000);  //sleep a million seconds so as not to interfere with current measurements.

It sleeps the MCU, and using just PPI, it wakes up the radio every 16 TICKS (each tick is 100ms) and measures the RSSI. Then it puts the radio back to sleep.

So, looking at the current consumption from a macro viewpoint, it's this:

The taller peaks are when the RSSI measurements happen. Zooming in on one of the RSSI measurements, the current consumption is this:

As you can see, very little, and only for a very short time!

NeverDie

So all I need now is a way for the PPI to compare the RSSI measurement it obtained above with a threshold benchmark to decide whether or not to wake the MCU, which can take it from there. From that point onward, the regular ESB code could be used. :)

NeverDie

Nordic could have taken this a lot farther if they had included some comparison tasks, so that the PPI could make decisions about what to do next. However, I don't see that there are any that can be used for comparing an RSSI measurement against a benchmark. Too bad. :(

Uhrheber

Great that it works.

But I'm not so convinced about the usefulness of this method, anyways.
I know that a lot of receivers use simple RSSI measurement to implement a low power listening mode, but when you are in a noisy environment, the system will wake up quite often, draining the battery fast. And unless you live in a very remote area, 2.4 GHz IS a noisy environment.

NeverDie

@Uhrheber said in nRF5 Bluetooth action!:

Great that it works.

But I'm not so convinced about the usefulness of this method, anyways.
I know that a lot of receivers use simple RSSI measurement to implement a low power listening mode, but when you are in a noisy environment, the system will wake up quite often, draining the battery fast. And unless you live in a very remote area, 2.4 GHz IS a noisy environment.

And your better alternative is....?

scalz

@NeverDie said in nRF5 Bluetooth action!:

From the view count, it does seem that people are reading this thread, even if not many are posting.

I'm following your work with interest of course ;) On my side i'm pretty busy on other stuff (rpi and my HA) so i'm missing time for try..I'll be back soon on this!

@NeverDie said in nRF5 Bluetooth action!:

t what to do next. However, I don't see

I thought too, about implementing this kind of listenmode for rfm69 in my HA. What i don't like so much, is I think i would need a dedicated node for the scheduling and it complicates a bit thing. I'm not fond of using gw resources for the wakeup broadcast.
I think, maybe I'm wrong, that, ideally, the best would be "time slots" so everything would be in sync, no flooding broadcast, lost msg, collisions etc.. but that implies some work regarding the lib, and some hw issues (with simple 8bits without precise rtc).

Keep the good work!

Uhrheber

@NeverDie None, unfortunately. The manufacturer would have to take care of that, by implementing a low power mode in the receiver (maybe with reduced sensitivity), and an additional low power wakeup pattern detector.
There are transceiver that can do that, but the nRF52 can't.

Some of the simple 433MHz OOK receivers have a low current consumption, but they're pretty insensitive, high bandwidth and low speed, so of not much use except switching some battery powered lamp, or such.

Some time ago I searched for a transceiver with low current receive mode, to use it in a battery powered node, that could be woken up by rf, but found nothing.
All of the standard data transceivers are pretty power hungry.

Toyman

Interesting study regarding nrf51/nrf52 power consumption:

https://www.google.ru/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&ved=0ahUKEwiYupPV06TWAhWBJZoKHR-jCO8QFgg-MAQ&url=http%3A%2F%2Fjournal-dl.com%2Fdownloadpdf%2F5910880e3fbb6e13743d5780&usg=AFQjCNGv9O3fK4NXNSxd7MD3Rkkm2Qu7bQ

nRF5 action!

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