Low Power¶

FreeRTOS applications on IPRO7 can use three power-saving states: WFI (FreeRTOS tickless idle), PDS (Power-Down Sleep, Level 31, which resumes in place) and HBN (Hibernate, which wakes through a cold boot). The SDK provides PDS entry and recovery through the prebuilt low-power framework hal_lp, and automatic WFI/PDS selection through ipro_pm. On the IPRO7AI Reef EVK you can measure the IPRO7AI's own current with SW8 and JP2; none of the shipped Reef configurations enters PDS.

Low-power modes¶

Architecture¶

Configuration¶

# CONFIG_USE_PSRAM is not set
CONFIG_HAL_LP=y
CONFIG_FREERTOS_IDLE_HOOK=y
CONFIG_PLATFORM_UART_BAUDRATE=115200

.config becomes autoconf.h as written; Kconfig dependencies are not applied, so write out every related key.

Test application ipro_lp_test¶

apps/test/ipro_lp_test is a minimal application without BLE or PSRAM that tests PDS Level 31 with RTC wake-up. It is configured for the IPRO7 EVB (CONFIG_EVB=y). Its lp shell commands cover the cases on this page: lp sleep <ms> (PDS through hal_lp), lp auto on|off (PDS when idle), lp status, lp mem [ms] (which OCRAM survives), lp misc on|off (keep the MISC domain powered), lp fastboot <ms> (HBN wake through cold boot) and lp wakectx. Read its src/lp_test_cli.c alongside this page.

Programming interface¶

This flow follows apps/platform/ipro7_demo/demo/soc/peripheral/lowpower_demo.c: initialize the framework, register a wake-up hook, and enter PDS with an RTC timer.

#include "hal_lp.h"

extern void shell_uart_reinit(void);
extern void vPortSetupTimerInterrupt(void);

static int wake_reinit(int wakeup_reason, void *arg)
{
    (void)wakeup_reason;
    (void)arg;
    shell_uart_reinit();          /* PDS reset the console UART */
    vPortSetupTimerInterrupt();   /* FreeRTOS system timer */
    /* Reinitialize other peripherals (I2C, SPI, ...) here */
    return 0;
}

int sleep_ms(uint32_t ms)
{
    static int initialized;
    if (!initialized) {
        if (hal_lp_init() != 0) {
            return -1;
        }
        hal_lp_register_wakeup_hook(wake_reinit, NULL);
        initialized = 1;
    }

    hal_lp_cfg_t cfg = {
        .rtc_wakeup_en    = 1,
        .rtc_sleep_us     = ms * 1000ULL,
        .flash_power_down = 1,
        .psram_retention  = 1,     /* keep PSRAM in self-refresh when present */
        .ocram_retention  = 1,
    };
    hal_lp_result_t res;
    int ret = hal_lp_enter(&cfg, &res);   /* wake reason (HAL_LP_WAKEUP_*) or a negative error */
    if (ret == HAL_LP_ERR_ENTRY_ABORTED) {
        /* An interrupt was pending; the chip never entered PDS (same as one WFI) */
    }
    return ret;
}

• hal_lp_result_t reports the wake reason, the GPIOs that triggered it and the actual sleep time; hal_lp_get_virtual_ms() gives a time base that continues across sleeps.
• GPIO wake-up: set gpio_wakeup_en and gpio_cfg (wakeup_mask, trigger, pull) in hal_lp_cfg_t; GPIO0–31 are available.
• The FreeRTOS tick count is not corrected for you after a sleep: add the actual sleep time back with xTaskCatchUpTicks(), as ipro_lp_test does.
• HBN: after hal_lp_enter_fastboot() the chip wakes through a cold boot, so the call never returns. At boot, check hal_lp_is_fastboot_wakeup() and read the wake context with hal_lp_get_wake_context(); anything that must survive has to be in HBN RAM first.

Retention and wake-up¶

• OCRAM: with the MISC domain powered down (the default), only the first 64 KB of OCRAM is retained through PDS31; pm_pds_set_misc_keep() keeps the MISC domain powered and retains all of OCRAM. Keep the data you need after wake-up in the first 64 KB, or keep MISC on, and check the result with lp mem in ipro_lp_test.
• PSRAM: psram_retention keeps PSRAM in self-refresh during PDS, and the framework restores it on wake-up. On IPRO7AI (the Reef's SoC) the PSRAM is inside the package and must stay in self-refresh through PDS.
• HBN RAM: 4 KB, the only memory kept through HBN; the framework's parameters and the fastboot wake context live there too.
• Console: UART0 sits in a domain that PDS31 resets, so reinitialize it after wake-up (shell_uart_reinit() or platform_init()). The console RX pin (GPIO21, U6 pin 4 on the Reef) cannot wake PDS, and characters typed during sleep are lost.
• GPIO wake-up: hal_lp supports GPIO0–31. The low-level pm_pds_gpio_wakeup_set() (hal_pm.h) accepts GPIO0–41, but pins share trigger settings in groups of four and only ASYNC triggers work (the SYNC ones need a clock that PDS stops). HBN wakes only from the AON pins.
• 32 kHz clock: RC32K by default; pm_pds_set_32k_src() switches to a 32 kHz crystal when the board has one. The Reef has none and runs from RC32K; the framework includes RC32K calibration.
• Flash: with flash_power_down = 1 the flash is powered down during sleep, and the framework restores XIP on wake-up.

BLE with sleep¶

• The BLE backend of ipro_pm and PDS during a BLE connection (CONFIG_IPRO_PM_BLE, CONFIG_IPRO_PM_PDS_CONNECTED) force a source build of the BLE controller. The controller ships only as prebuilt libraries, so these cannot be built from the package. For products that need low power during BLE connections, contact INTELPRO.
• ipro_ble_remote/defconfig_reef deliberately runs without PDS: the Reef is USB-powered, and its camera and audio need the clocks.
• ipro_pdm_mic_demo (IPRO7 EVB, IPRO7AI EVK) shows BLE with tickless WFI and a manual pds [sec] command.
• For BLE controller variants, Exchange Memory size and other BLE settings, see BLE Development.

Measuring¶

• Measure in the SoC's supply path with an external meter. On the Reef, SW8 and JP2 route the IPRO7AI's 3.3 V through the meter (walk-through below); other boards are covered in Power & Current Measurement.
• Confirm how often and how long the chip actually sleeps, and log the wake reason (hal_lp_result_t). If it wakes more often than expected, look for timers and pending interrupts first (hal_lp_enter() returns HAL_LP_ERR_ENTRY_ABORTED).
• With ipro_pm, pm stats lists the residency in each mode and an estimated current. The estimate is for comparing configurations only; it does not replace a measurement.
• Compare the same firmware under WFI and under PDS, and let UART output finish before sleeping so that it is not cut off.

Hands-on on the Reef¶

Measure how much current the IPRO7AI draws while your firmware runs. No shipped Reef configuration enters PDS, so this walk-through uses the out-of-box firmware and compares an idle shell with the camera pipeline running; repeat it with your own application to get its baseline before you add sleep.

You need an ammeter (or a source-measure unit) with leads for the 3-pin JP2 header.

Next: start your own application with Create Your First Application, and check its behavior and current with Test Your Application.

Limitations in this release¶

• No shipped IPRO7AI Reef EVK configuration enters PDS or HBN; ipro_lp_test and the ipro7_demo low-power commands target the IPRO7 EVB.
• PDS during a BLE connection cannot be built from the package (controller source build).
• No low-power modes under Zephyr RTOS (pm_state does not enter PDS or HBN); see Zephyr RTOS.
• CONFIG_IPRO_PM_IDLE_PDS (PDS entered by the idle task) has no shipped example; validate it on your board before use.
• The low-power memory layouts cannot be combined with the HOTCODE options.

Related documents¶

• IPRO7AI Reef EVK: SW8, JP2 and the current-measurement procedure.
• Power & Current Measurement
• BLE Development
• Build System & Configuration
• Zephyr RTOS