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.