NRF52832/52810 System OFF wakeup issue

RE: NRF52832/52810 System OFF wakeup issue

Einar Thorsrud — Fri, 14 Jun 2019 11:02:03 GMT

Hi,

The key thing is that the nRF GPIO can be configured with internal pull-up, pull-down or no pull resistor at all. This gives you full flexibility, so it is all up to you to design this. Please refer to my post from yesterday for suggestions about how you can do it.

RE: NRF52832/52810 System OFF wakeup issue

bevis — Fri, 14 Jun 2019 10:45:30 GMT

What should we do? Are you talking about the high impedance state as pull-down input or something else? On the other hand, if I take an external pull-up input, in order to trigger the edge, my MCU must set no pull or pull down.

RE: NRF52832/52810 System OFF wakeup issue

Einar Thorsrud — Fri, 14 Jun 2019 08:50:27 GMT

Hi,

The internal pull resistor is optional. You can disable it if you like, and in that case, the input is high impedance (virtually no leakage). So, it is entirely up to you to design the HW to match your needs.

RE: NRF52832/52810 System OFF wakeup issue

bevis — Fri, 14 Jun 2019 08:40:04 GMT

I have tried 10K, voltage is 1.7V, shaking can produce 1.7V - > 3V rising edge pulse, but when the sensor is still off, leakage is about 200 ua. When I increase to 100K, voltage is 2.6V, shaking can produce 2.6 - > 3V rising edge, although the leakage current is reduced to 100ua, setting high sense at this time will lead to no access to s. System off, if sense low is set, the system will not wake up. Was the system off designed without considering that some sensors were on?Because this sensor is always on, it causes the leakage of the pull-up input. I changed to turn on mode when dormant 1.9ua, but the wake-up conditions I still need to induction logic level pulse, or to face the leakage problem, I do not know how to deal with now.

RE: NRF52832/52810 System OFF wakeup issue

Einar Thorsrud — Fri, 14 Jun 2019 07:54:23 GMT

I see. As mentioned, the nRF GPIO input is high impedance (unless you count the optional pull resistor, which is ~13 kΩ), so it is up to you to design a circuit that provided valid logic levels to the nRF.

RE: NRF52832/52810 System OFF wakeup issue

bevis — Thu, 13 Jun 2019 13:54:07 GMT

RE: NRF52832/52810 System OFF wakeup issue

bevis — Thu, 13 Jun 2019 13:51:59 GMT

As you said, the voltage between Rser and Rpull is logical low level < 0.7*VDD = 2.1. I'm adjusting 1.7V. When shake the vibration sensor, GPIO can detect the rising edge pulse to 1.7V - > 3V, because I set GPIO as the pull-up input. Because of setting up pull-up input, Rpull and GND generate a 100-200ua leakage current. This is very troublesome when it comes to system off. By the way, the sensor is also connected to GND.

RE: NRF52832/52810 System OFF wakeup issue

Einar Thorsrud — Thu, 13 Jun 2019 13:26:13 GMT

Hi,

I am not sure I understood you correctly, but from what I understood you have connected the sensor as shown below, via a serial resistor and then the pull-down resistor:

This constitutes a voltage divider, so depending on the resistor values, you will get an invalid voltage level at the input on the nRF.

I don't know any details of your design, but generally, you can fix this in one of the following ways:

Make sure that Rser is much smaller then Rpull, so that the voltage between will still be within the valid region.
Remove Rser (if it is not needed)
Use an external pull resistor and move Rpull before Rser. The nRF GPIO input is high impedance and draws virtually no current, so it should not have much impact on the voltage in this case.

RE: NRF52832/52810 System OFF wakeup issue

bevis — Thu, 13 Jun 2019 07:16:08 GMT

My shake sensor is connected in series with a resistor connected to GND. The input is set to a pull-up input. One problem is that when my sensor off, the detection pin is pulled down. At this time, I set it to a high level to detect NRF_GPIO_PIN_SENSE_HIGH.(Resistance changes during vibration increase the level of pin detection),it works. But when the sensor off, because of the direct connection to GND and the pull-up input relationship, the leakage current is 200 ua, and the pull-down resistance isolation is at least 100 + ua, which will lead to the level mismatch and can not wake up normally. What can I do to solve the leakage problem? Or is there any better way to wake up?

RE: NRF52832/52810 System OFF wakeup issue

Einar Thorsrud — Tue, 21 May 2019 12:30:19 GMT

[quote user="Z388225"]Does it mean that when the external input signal remains high or low, the system will always be awakened and unable to sleep?[/quote]

No. You configure the sense mechanism to detect one level. For instance, if the pin state is normally low and you want to wake up when it is high, then you use NRF_GPIO_PIN_SENSE_HIGH. And vice versa. You should of course also make sure that the pin is never floating. So if there is not always a input signal, then you must use a (internal) pull resistor.

RE: NRF52832/52810 System OFF wakeup issue

bevis — Tue, 21 May 2019 12:22:13 GMT

“Sense on the other hand is a GPIO feature that allows the pin to detect/sense a voltage level (high or low) and wake up form system OFF when it does.” Does it mean that when the external input signal remains high or low, the system will always be awakened and unable to sleep?

RE: NRF52832/52810 System OFF wakeup issue

Einar Thorsrud — Tue, 21 May 2019 12:16:55 GMT

Hi,

The GPIO sense mechanism is unrelated to the GPIOTE peripheral. GPIOTE requires a clock, and cannot be used in system OFF. Sense on the other hand is a GPIO feature that allows the pin to detect/sense a voltage level (high or low) and wake up form system OFF when it does. The sense mechanism is configured for instance with nrf_gpio_cfg_sense_set(), or using nrf_gpio_cfg_sense_input() to set up everything with a single function. Essentially this writes the configuration to the corresponding PIN_CNF register.

RE: NRF52832/52810 System OFF wakeup issue

bevis — Tue, 21 May 2019 11:55:15 GMT

Thank you for your prompt. By the way, what's the difference between nrf_drv_gpiote_in_init and nrf_gpio_cfg_sense_set? The former is familiar to me, and the latter has been exploring???

RE: NRF52832/52810 System OFF wakeup issue

Einar Thorsrud — Tue, 21 May 2019 11:50:13 GMT

Hi,

I did not fully understand the question, so please elaborate and ask again if the following does not answer it.

The GPIO sense mechanism can be used as a wake up source from system off mode, and it can detect either a high or a low level. This pulse can be quite short (exactly how short is not documented) and wake up the device from system off. So if you have a bit of noise on the input, then this will typically wake up the system.