Low Power UART Example with HFC

[Sivashankar]

Hi,

https://devzone.nordicsemi.com/f/nordic-q-a/68842/how-to-achieve-ble-with-beacon-low-power-uart-communication

https://devzone.nordicsemi.com/f/nordic-q-a/27147/how-to-configure-uart-with-low-power

https://devzone.nordicsemi.com/f/nordic-q-a/47578/nrf52832-uart-power-consumption

https://devzone.nordicsemi.com/f/nordic-q-a/43684/why-is-uart-without-dma-deprecated

https://devzone.nordicsemi.com/f/nordic-q-a/35510/uart-deinit-does-not-reduce-power-consumption-and-it-too-big-600ua

https://devzone.nordicsemi.com/f/nordic-q-a/26030/how-to-reach-nrf52840-uarte-current-supply-specification/102605#102605

https://devzone.nordicsemi.com/f/nordic-q-a/19284/turn-off-uart-on-nrf52832

After referring to number of low power UART discussions above I still have a question, Is there any direct low power UART example which demonstrates the electrical character as specified in Datasheet.(Just for nrf52xxx DK)

I was trying to optimize power for my app(link) which was initially consuming 6mA/1mA for Adv/Conn. After Enabling DCDC it was around 600uA/540uA or Adv/Conn.

After Just disabling UART it was just 100uA/60uA for Adv/Conn, so the UART alone consume 500uA. After all read through I disabled EasyDMA and removed UARTE(Used UART) and saved ~150uA.

So my total power now is around 435uA/360uA for Adv/Conn. After which I thought enabling Hardware flow control may save me more power, but surprisingly the current increased by 70-150uA  after enabling HFC. I don't understand why.

To be precise, the answer I'm looking for is: How do I Enable and Disable UART with Respect to RTS/CTS so that reduce active UART time and save power.

[Sivashankar]

I want UART Rx to be waked up with RTS and UART Tx at BLE events. So I don't want UART to be closed/Disabled. 

Usually I work with MSP, where I'll attach interrupt to UART_Rx which wake up and add received byte in buffer and sleep. It saves me lot of power there.

Not sure will the same kind of approach is possible here. 

[Sigurd]

Hi,

In addition to the post you have linked to, also see these:

https://devzone.nordicsemi.com/f/nordic-q-a/69357/nrf52840-uart-current-consumption-in-datasheet

https://devzone.nordicsemi.com/f/nordic-q-a/66914/uart-current-consumption/

For NCS I recommend using the LP-UART driver:

http://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.6.1/nrf/drivers/uart_nrf_sw_lpuart.html

For nRF5-SDK, the examples here might be useful: https://github.com/NordicPlayground/nrf51-UART-examples/tree/master/ble_app_uart_low_power

[Sivashankar]

Hi Sigurd,

Sigurd said:

In addition to the post you have linked to, also see these:

https://devzone.nordicsemi.com/f/nordic-q-a/69357/nrf52840-uart-current-consumption-in-datasheet

https://devzone.nordicsemi.com/f/nordic-q-a/66914/uart-current-consumption/

Thanks for the references, Question with them again is, If we want to us a GPIO for enabling and disabling UART means what's the purpose of RTS/CTS(Hardware flow control pins) and why is there increase in current after enabling HFC

Sigurd said:

For NCS I recommend using the LP-UART driver:

http://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.6.1/nrf/drivers/uart_nrf_sw_lpuart.html

I may be asking very basic questions as I'm quit new to nordic, Please excuse if I'm silly. 

1. Can I use samples/peripheral/lpuart   with my existing app, currently I'm using nrf_SDK 17.0.2, so bit confused how to import nrf_connect lib and drivers.

2. On a overview with LP-UART example(https://github.com/nrfconnect/sdk-nrf/blob/master/samples/peripheral/lpuart/src/main.c) Can I implement it with hardware flow control?

3. Is there any current measurement taken with this example (say with nrf52840 dk) ?

Sigurd said:

For nRF5-SDK, the examples here might be useful: https://github.com/NordicPlayground/nrf51-UART-examples/tree/master/ble_app_uart_low_power

Have seen this reference with many post, and ignored as it was around 7 years old reference, do you still recommend spending time, inferring this reference. 

[Sigurd]

Sivashankar said:

1. Can I use samples/peripheral/lpuart   with my existing app, currently I'm using nrf_SDK 17.0.2, so bit confused how to import nrf_connect lib and drivers.

 No, it's 2 different SDK's and cannot be combined easily.

Sivashankar said:

Can I implement it with hardware flow control?

From the doc: "The protocol used by this driver implements two control lines, instead of standard hardware flow control lines, to allow for disabling the UART receiver during the idle period. "

What is the use-case for using UART in your application? Connect to a different microcontroller, and both sending and receiving data? If yes, what microcontroller are you using, 2 different nRF52?  OR is the use-case e.g. logging?

 

[Sivashankar]

Sigurd said:

No, it's 2 different SDK's and cannot be combined easily.

If so can you recommend/refer me some examples which would make sense to app developed in nrf_SDK 17.0.2. A simple LPUART with nrf_SDK 17.0.2.

I can able to see LP_PWM in \nRF5_SDK_17.0.2_d674dde\examples\peripheral but no LP_UART.

Could you please consider this as user request to add one such example in nRF5_SDK_xx.xx.xx.

[Sigurd]

Sivashankar said:

Could you please consider this as user request to add one such example in nRF5_SDK_xx.xx.xx.

 I can forward such an request, but our focus is mainly on nRF Connect SDK(NCS) now, so most likely there will not be such an example in nRF5 SDK anytime soon

[Sivashankar]

Sigurd said:

I can forward such an request, but our focus is mainly on nRF Connect SDK(NCS) now, so most likely there will not be such an example in nRF5 SDK anytime soon

So It's recommend to start developing the application with nRF Connect SDK and stop using nRF5_SDK.