nrf9160 uart Pull-Up and power consumption

[MosheSmartAmr]

hi all,

i'm trying to disable uart for lower power consumption, i've disables it with:

NRF_UARTE1->TASKS_STOPTX = 1;
NRF_UARTE1->TASKS_STOPRX = 1;

but when i measure the voltage on the rx pin i see 1.8V  (this seems to consume current on the device on the other side of the uart interface - which is turned off )
i assume its in pulled up state, so i'm trying to change it's state to no-pull:

nrf_uarte_txrx_pins_disconnect(NRF_UARTE0);
gpio_pin_configure(uart_wifi, 18, GPIO_PUD_PULL_DOWN);
gpio_pin_configure(uart_wifi, 19, GPIO_PUD_PULL_DOWN);
gpio_pin_write(uart_wifi, 18,0);
gpio_pin_write(uart_wifi, 19,0);

 but it doesnt seem to have any effect.

how can i set this pin to 0, and back to 1 when I need it , on runtime?

Thanks

Moshe

[Vidar Berg]

Hi Moshe, 

Is the external IC power gated? It should drive the RX line to 'high' when it's inactive and powered. So that may explain why you see the current draw when you set the output to 0. 

Also, from your code snippets, it appears that you are stopping UART instance 1 while nrf_uarte_txrx_pins_disconnect() call takes instance 0 as an argument. Not sure if this is intended or not.

Best regards,

Vidar

[MosheSmartAmr]

Hi Vidar,

Thanks for your answer, 

1. I called `nrf_uarte_txrx_pins_disconnect()` on both UARTs (didnt copy it into the snippet).

2. I test this while the external IC is powered off  (it is gated ) . 

3. Just to be clear, even when I  disable UART from the SW, I still measure 1.8v on the TX pin . I guess it is still pulled up . 

Thanks and BR

[Håkon Alseth]

Hi,

 

This should not affect the PSM mode, but it might affect the application in terms of sleep routines.

Is there anything specific that happens when you have disabled the UART? Are you able to see if the nRF9160 is awoken from sleep by anything unpredictable?

 

Kind regards,

Håkon

[MosheSmartAmr]

I don't see any reason that the NRF91 will be awaken once I disable uart. 

could the uart module do that internally? is there a way to disable the uart's module ability to interrupt the NRF91 from sleep ?

[Håkon Alseth]

You can clear the events that are set (EVENTS_*), disable the interrupts (Write 0xFFFFFFFF to NRF_UARTEx->INTENCLR), and see if this has any effect.

[MosheSmartAmr]

unfortunately that did not work. 

still getting the same consumption

[Håkon Alseth]

If the current consumption does not come from VDD_IO, then it should not be related to the IO settings at all, but more in the program flow.

Is there any functions running after disabling the uart which tries to use it again? So that the firmware goes into a bad state, causing the high current consumption?

 

If you're unsure if this comes from VDD_IO, could you try setting it to a input instead of output?

// Input, connected, with pull-down
NRF_P0_NS->PIN_CNF[pin_used] = 0x4;

 

Kind regards,

Håkon

[MosheSmartAmr]

Thanks  Hakon,

Your last answer seemed to direct me to the answer, 

there was an issue with the SW flow,

which leaves the question, is there a way to get an event / interrupt when leaving sleep mode (so I can re-enable uart) ? 

Kind Regards ,

Moshe

[MosheSmartAmr]

also how do I re-enable uart after the code you suggested above.

(specifically after setting NRF_P0_NS->OUTCLR = (1 << TXD_PIN);)

[Håkon Alseth]

Hi,

  

MosheSmartAmr said:

also how do I re-enable uart after the code you suggested above.

 You store the INTENCLR mask, then set that via INTENSET, and the same goes to all other parameters that are "unset" from the disable function. Note that you strictly do not need to clear the PSEL registers. Then you start the TX and RX via its respective tasks.

 

There are events that can be generated when entering/exiting sleep, in the POWER peripheral:

https://infocenter.nordicsemi.com/topic/ps_nrf9160/power.html?cp=2_0_0_4_2_0

However; they are not really meant to enable interrupts on, as that would again wake you up, thus it'll defeat the purpose if you hook onto these events to do CPU processing. They are however very useful to see how often the CPU sleeps if you set/clear a GPIO on these events via PPI and GPIOTE, and look at it using a logic analyzer.

 

Kind regards,

Håkon

[MosheSmartAmr]

Hi Hakon,

Do I need any special handling if I am using the UART DMA? 

it seems to go wrong when I disable and enable it .

i.e. 

1. if I disable UART  before sending/receiving, i get stuck on  while(NRF_UARTE1->EVENTS_RXTO==0); after stopping RX.

2. lf it is disabled after an initial connection, I receive garbage from the uart.

any suggestions? 

[Håkon Alseth]

Could you post your enable and disable routine? 

MosheSmartAmr said:

if I disable UART  before sending/receiving, i get stuck on  while(NRF_UARTE1->EVENTS_RXTO==0); after stopping RX.

Try setting the event to 0 before stopping the RX: 

NRF_UARTEx->EVENTS_RXTO = 0; 
NRF_UARTEx->TASKS_STOPRX = 1; 
while(NRF_UARTEx->EVENTS_RXTO==0);

 

Kind regards,

Håkon