Lowest Power Mode nRF52840

[Jigar]

Hello,

I have been trying different mode under SYSTEM ON configurations and I can not get anything below 1mA. 

My application required to keep nRF52840 (I use BMD-340) ON all the time with lowest power consumption with Active BLE.

Once I get connection from central BLE , I need to do following

1> Wake up external micro to transfer data over UART

2> Transfer Data to central BLE

3> Go back to low power mode.

Can someone please  help me out with best solution available?

I would be really grateful if you provide any type of Example.

Thanks

Jay  

[Jigar]

Hello,

Once I disable UART using 

uint32_t err_code = app_uart_close();
if ( err_code == NRF_SUCCESS ) {
NRF_UART0->TASKS_STOPTX = 1;
NRF_UART0->TASKS_STOPRX = 1;
NRF_UART0->ENABLE = 0;
/* Workaround by disabling the UART peripherals due to Nordic SDK15.0 issue */
*(volatile uint32_t *)0x40002FFC = 0; /* Power down UARTE0 */
*(volatile uint32_t *)0x40002FFC;
*(volatile uint32_t *)0x40002FFC = 1; /* Power on UARTE0 so it is ready for next time */

It works Great. But Then when I try to enable UART module after SLeep using following code

// Re-enable UART
NRF_UART0->ENABLE = UART_ENABLE_ENABLE_Enabled << UART_ENABLE_ENABLE_Pos;

// Enable UART transmission and reception
NRF_UART0->TASKS_STARTRX = 1;
NRF_UART0->TASKS_STARTTX = 1;

But It does not activate UART. Can you please advise? I have to re-initialize UART using UART_init()? Which Init FIFO_UART buffers also.

Thanks

Jay

[Einar Thorsrud]

Hi Jay,

Yes, you need to re-init the UART driver after doing the writes to 0x40002FFC, and re-init it completely afterward. The reason is that the workaround you use effectively power-cycles the peripheral, so you must configure it again before it can be used.

[Jigar]

Thanks Einar,

Do I need to Re-Init any other peripheral? Also, Is it OK to call FIFO every time when we re-init? It may cause some problem. Is there any other solution?

Thanks

Jay