Concepts First

• Low-power modes: when the chip has nothing to do, it "sleeps" and turns off most circuits to save power. BL616/BL618 mainly provide PDS (light sleep, peripherals powered down) and HBN (hibernate, only the AON domain runs).
• Timed wake-up: the 32K clock keeps running during sleep; the RTC wakes the chip after the configured time. The example wakes every 1 second.
• Wake-up sources: the "alarms" that can wake the chip — RTC timer, GPIO edges/levels, BOD brown-out detection, etc. The example masks all sources with pm_pds_mask_all_wakeup_src() and enables the RTC timer via the sleep-time argument of pm_pds_mode_enter.
• Sleep-time unit: pm_pds_mode_enter's sleep_time is in 32K clock cycles (32768 cycles = 1 second); the example uses 32768 * 1.

Example Overview

This page is based on the pds_rtc example in the official Bouffalo SDK (examples/pmu/bl616/pds_rtc), which demonstrates PDS deep sleep + RTC timed wake-up:

• Before sleeping: disables the USB PHY power switch, masks all wake-up sources, floats the RF LDO15 output, and masks HBN pin wake-ups;
• Prints enter pds mode, then calls pm_pds_mode_enter(PM_PDS_LEVEL_15, 32768 * 1) to enter PDS level 15, the deepest sleep level;
• Wakes every 1 second via the RTC timer and re-runs the main flow — a periodic wake-up loop;
• To measure power, put a multimeter in series with the supply and observe the sleep current (far lower than normal operation).
• Sibling examples (examples/pmu/bl616/): hbn_rtc (HBN deep sleep + RTC wake-up), hbn_io_wakeup (HBN + GPIO wake-up), pds_io_wakeup (PDS + GPIO wake-up).

Note

Serial output pauses during sleep and only appears at the wake-up moment; that is normal. Do not unplug the debug cable while observing, since the debug power may affect current measurements.

Operation Steps

1

Enter the Example Directory

No external wiring is needed for this page. Open a terminal and enter the SDK PDS sleep example directory (prerequisite: set up the environment as in Quick Start (Linux) or Windows):

cd examples/pmu/bl616/pds_rtc

2

Build the Project

Run the build command. The Ai-M62 (BL616) and Ai-M61 (BL618) belong to the same series, so both use bl616:

make CHIP=bl616 BOARD=bl616dk

3

Flash the Firmware

Connect the board with a USB cable, hold the BOOT button (IO2 on the Ai-M61-32S-Kit), briefly press EN/RST to enter download mode, then flash (replace the serial port with the one on your computer):

make flash CHIP=bl616 COMX=/dev/ttyUSB0

4

Run and Verify

Open a serial tool (baud rate 2000000). The program prints enter pds mode and enters PDS deep sleep; the RTC timer wakes it 1 second later, it prints the same message, and sleeps again — a 1-second wake-up loop you can observe on the serial port.

Code Execution Flow

The complete flow from startup to sleep and timed wake-up is shown below (loop arrows mean repeated execution):

APIs Used by the Example

BL_RD_REG / BL_CLR_REG_BIT / BL_WR_REG(base, reg / bit / val)

Register bit macros: BL_RD_REG reads a register, BL_CLR_REG_BIT clears a bit, BL_WR_REG writes back. The example uses them to disable the USB PHY power switch bit PDS_REG_PU_USB20_PSW.

Parameters:

• base: register base (PDS_BASE in the example)
• reg: register offset (PDS_USB_PHY_CTRL in the example)
• val: value / bit number

Return: BL_RD_REG returns the register value; the macros return nothing

pm_pds_mask_all_wakeup_src()

Masks (disables) all PDS wake-up sources to avoid spurious wake-ups. The example then enables RTC timed wake-up only through the sleep-time argument of pm_pds_mode_enter.

Parameters: none

Return: none

AON_Output_Float_LDO15_RF()

Floats the LDO15 output that powers RF, reducing power further during sleep.

Parameters: none

Return: BL_Err_Type (SUCCESS is 0)

HBN_Pin_WakeUp_Mask(0xF)

Masks HBN (AON) pin wake-ups: 0xF masks all four wake-up pins (IO16–IO19).

Parameters:

• maskVal: pin mask; bits set to 1 disable wake-up on that pin

Return: BL_Err_Type

pm_pds_mode_enter(pds_level, sleep_time)

Enters PDS sleep. sleep_time is in 32K clock cycles (32768 = 1 second); 0 disables RTC timed wake-up, so another source (e.g. GPIO) must wake the chip.

Parameters:

• pds_level: sleep level, PM_PDS_LEVEL_15 (deepest) in the example
• sleep_time: sleep duration in 32K cycles, 32768 * 1 (1 second) in the example

Return: none

Complete Code

The complete source below matches the official example (examples/pmu/bl616/pds_rtc) verbatim. Collapsed by default, click to expand:

📜 Click to expand pds_rtc/main.c full code

#include "bflb_mtimer.h"
#include "board.h"
#include "log.h"
#include "bl616_glb.h"
#include "bl616_pds.h"
#include "bl616_hbn.h"
#include "bl616_aon.h"
#include "bl616_pm.h"

int main(void)
{
    uint32_t tmpVal = 0;
    board_init();

    /* rf808_usb20_psw_rref output off */
    tmpVal = BL_RD_REG(PDS_BASE, PDS_USB_PHY_CTRL);
    tmpVal = BL_CLR_REG_BIT(tmpVal, PDS_REG_PU_USB20_PSW);
    BL_WR_REG(PDS_BASE, PDS_USB_PHY_CTRL, tmpVal);

    pm_pds_mask_all_wakeup_src();
    AON_Output_Float_LDO15_RF();
    HBN_Pin_WakeUp_Mask(0xF);

    printf("enter pds mode\r\n");
    bflb_mtimer_delay_ms(100);

    /* Wake up every 1 seconds by pds15 */
    pm_pds_mode_enter(PM_PDS_LEVEL_15, 32768 * 1);

    while (1) {
    }
}

FAQ

The chip never wakes up

Check the wake-up configuration: if sleep_time in pm_pds_mode_enter is 0 there is no timed wake-up — you must enable a GPIO or another wake-up source. Also make sure you did not mask everything with pm_pds_mask_all_wakeup_src() and forget to enable the source you need.

The wake-up period is not 1 second

sleep_time is in 32K cycles. If the 32K clock is inaccurate (uncalibrated RC 32K), the interval drifts; for high accuracy use an external 32.768 kHz crystal or calibrate with pm_rc32k_auto_cal().

What is the difference between PDS and HBN

PDS is lighter and wakes faster; peripherals lose power but SRAM contents are kept. HBN (hibernate) keeps only the AON domain and consumes the least power. Battery-powered periodic reporting often combines both: HBN most of the time, waking into PDS to handle tasks.

Have questions?

For any other questions, visit the unified Q&A and discussion board: Ai-Thinker Discussions