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  

[WestCoastDaz]

jigar

Are you measuring the 1mA with a power profile kit?  If not how are you measuring this?

The BLE peripheral examples in the SDK folder are power optimized to some extent so they are always a good place to start.

Cheers,

Darren

[Jigar]

Hello,

I have 1 Ohm in series at VCC to measure total current for BMD-340 module. I have tried using Nordic SDK and one exmple power management but that is System OFF example and still I did not see huge difference. Can you please advise if i am doing something wrong?

I want possible lowest power while my BLE is ON and based on Connection I can turn ON/OFF my GPIO.

Thanks

Jay

[Jigar]

Hello,

I tried your solution and it is in uA. (So, H/W Looks OK) I have also verified NRF_LOG_ENABLED  is set to 0.

Here is how my code looks like.

main

uart_init();
log_init();
timers_init();
buttons_leds_init(&erase_bonds);
power_management_init();
ble_stack_init();
gap_params_init();
gatt_init();
services_init();
advertising_init();
conn_params_init();
nrf_delay_ms(1000);

// Start execution.
// printf("\r\nUART started.\r\n");
// NRF_LOG_INFO("Debug logging for UART over RTT started.");
err_code = advertising_start();
disabled_uart();
// Enter main loop.
for (;;) {
idle_state_handle();

In Above case my current is 1.3mA.

If I comment  uart_init() my current is 300uA.

Even tough, I have disabled_uart() which is as below It does not disable UART

uint32_t err_code = app_uart_close();
// APP_ERROR_CHECK(err_code);
NRF_UART0->TASKS_STOPTX = 1;
NRF_UART0->TASKS_STOPRX = 1;
NRF_UART0->ENABLE = 0;

Please advise.

Thanks

Jay

[Einar Thorsrud]

Hi Jay,

The UART peripheral should be disabled when not used, if not it will cause a high current consumption, as you mention. When you write that the current consumption is 300 uA when you comment out uart_init(), I assume you comment out all other UART related code as well (e.g. writing to UART0 registers)?

It is a bit difficult to follow the code snippets in the last post, since I don't see the full context, but I do not see anything obvious other than UART that we have already discussed. One possible relevant point is if any LED's are lit on the board? If not, can you simply comment out everything and then start uncommenting again to narrow down which part of the code causes the high current consumption (the 300 uA after UART is disabled)?

Einar

[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