UARTs and EASY DMA

[abe]

Hi, I'm trying to use two UART instances, and I have the following issues:
- I'm not be able to configure both instance using NRF_SERIAL_CONFIG_DEF macro with parameter NRF_SERIAL_MODE_IRQ. As result of nrf_serial_init function call on the UART1 instance, the init function returns err code 8 (NRF_ERROR_INVALID_STATE).
- Instead, if I use the NRF_SERIAL_CONFIG_DEF macro with parameter NRF_SERIAL_MODE_DMA the two UART instances work well.
- With EASY_DMA, the current sink in sleep mode is 300uA more. In case of UART + EASY_DMA, during sleep mode, the sink of CPU current is about 1mA.
- If the two UARTs is not enabled (do not call any initialization functions), the current sink in sleep mode is about 2uA.
Where I wrong?
How can I have few uA of CPU current comsumption even with UARTs enabled?
Many thanks for help

Abele

[Amanda Hsieh]

Hi, 

- I'm not be able to configure both instance using NRF_SERIAL_CONFIG_DEF macro with parameter NRF_SERIAL_MODE_IRQ.

 That's right. UART1 is not supported. Serial peripheral with number 1 is only UARTE1 in nRF52840 SoC.

- Instead, if I use the NRF_SERIAL_CONFIG_DEF macro with parameter NRF_SERIAL_MODE_DMA the two UART instances work well.

You also can take a look at this Serial Port Library Example with two UARTEs example. 

How can I have few uA of CPU current comsumption even with UARTs enabled?

 

if you use the UART, it needs to turn on the UART (50uA) from the Product spec + high frequency clock.

https://jimmywongbluetooth.wordpress.com/2019/04/17/overview-uart-driver-handling-at-nrf52/

My colleague did some measurements on the Legacy UART or UART with DMA.

Please also see this post. 

Could you show us who you measured the current? What is the code you use?

-Amanda H.

[abe]

Amanda,

I readed both link you sent me. In the UART driver handling article for nRF52 yuo can understand the current sink in the following two case:
- UARTE with DMA --> average 1.3mA
- UART (Legacy) --> average 373uA
These are EXACTLY the currents I have measured on my application for the two method above quoted.
I think that the only way to reduce the current sink is to disable the UART
It's right? How can I disable the UART?

[Amanda Hsieh]

You could use nrfx_uart_uninit to uninitialize the UART driver.

-Amanda H.