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Merge pull request #77 from sparkfun/lowPower
Add examples demoing low power config
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‎libraries/Examples/examples/Advanced/LowPower/LowPower.ino

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/*
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Artemis Low Power: How low can we go?
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By: Nathan Seidle
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SparkFun Electronics
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Date: October 17th, 2019
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License: This code is public domain. Based on deepsleep.c from Ambiq SDK v2.2.0.
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A big thanks to robin_hodgson for pointing out the HFRC shutdown requirement.
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SparkFun labored with love to create this code. Feel like supporting open source hardware?
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Buy a board from SparkFun! https://www.sparkfun.com/products/15376
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How close can we get to 2.7uA in deep sleep?
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This example shows how decrease the Artemis current consumption to less than ~2.5uA in deep sleep.
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Note that Artemis modules with revision A1 silicon will use ~30uA. Please see the
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Ambiq errata for more information: https://www.ambiqmicro.com/static/mcu/files/Apollo3_Blue_Errata_List_v1_0_external_release.pdf
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To monitor the current to the Edge cut the MEAS jumper, solder in headers, and attach
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a DMM via IC hooks (https://www.sparkfun.com/products/506).
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The USB to serial bridge draws some current:
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Serial Basic C - ~1.2uA (https://www.sparkfun.com/products/15096)
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FTDI Basic - ~5.5uA (https://www.sparkfun.com/products/9873)
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The various components on the Edge2 can be powered on/off as well
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PDM microphones (2) - ~50.9uA
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Accelerometer (POR mode) - ~79.7uA
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Camera regulator enabled (no camera) - ~96.8uA
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*/
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void setup()
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{
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Serial.begin(115200);
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Serial.println("Low power sleep example");
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#if defined(ARDUINO_SFE_EDGE2)
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pinMode(ACCEL_VDD, OUTPUT);
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digitalWrite(ACCEL_VDD, LOW);
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pinMode(MIC_VDD, OUTPUT);
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digitalWrite(MIC_VDD, LOW);
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pinMode(CAMERA_VDD, OUTPUT);
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digitalWrite(CAMERA_VDD, LOW);
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#endif
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//Turn off ADC
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power_adc_disable();
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// Initialize for low power in the power control block
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am_hal_pwrctrl_low_power_init();
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// Stop the XTAL.
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am_hal_clkgen_control(AM_HAL_CLKGEN_CONTROL_XTAL_STOP, 0);
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// Disable the RTC.
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am_hal_rtc_osc_disable();
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// Disabling the debugger GPIOs saves about 1.2 uA total:
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am_hal_gpio_pinconfig(20 /* SWDCLK */, g_AM_HAL_GPIO_DISABLE);
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am_hal_gpio_pinconfig(21 /* SWDIO */, g_AM_HAL_GPIO_DISABLE);
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// These two GPIOs are critical: the TX/RX connections between the Artemis module and the CH340S on the Blackboard
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// are prone to backfeeding each other. To stop this from happening, we must reconfigure those pins as GPIOs
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// and then disable them completely:
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am_hal_gpio_pinconfig(48 /* TXO-0 */, g_AM_HAL_GPIO_DISABLE);
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am_hal_gpio_pinconfig(49 /* RXI-0 */, g_AM_HAL_GPIO_DISABLE);
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// The default Arduino environment runs the System Timer (STIMER) off the 48 MHZ HFRC clock source.
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// The HFRC appears to take over 60 uA when it is running, so this is a big source of extra
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// current consumption in deep sleep.
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// For systems that might want to use the STIMER to generate a periodic wakeup, it needs to be left running.
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// However, it does not have to run at 48 MHz. If we reconfigure STIMER (system timer) to use the 32768 Hz
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// XTAL clock source instead the measured deepsleep power drops by about 64 uA.
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am_hal_stimer_config(AM_HAL_STIMER_CFG_CLEAR | AM_HAL_STIMER_CFG_FREEZE);
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// This option selects 32768 Hz via crystal osc. This appears to cost about 0.1 uA versus selecting "no clock"
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am_hal_stimer_config(AM_HAL_STIMER_XTAL_32KHZ);
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// This option would be available to systems that don't care about passing time, but might be set
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// to wake up on a GPIO transition interrupt.
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// am_hal_stimer_config(AM_HAL_STIMER_NO_CLK);
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// Turn OFF Flash1
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if (am_hal_pwrctrl_memory_enable(AM_HAL_PWRCTRL_MEM_FLASH_512K))
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{
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while (1)
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;
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}
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// Power down SRAM
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PWRCTRL->MEMPWDINSLEEP_b.SRAMPWDSLP = PWRCTRL_MEMPWDINSLEEP_SRAMPWDSLP_ALLBUTLOWER32K;
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Serial.println("Going to sleep...");
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delay(100); //Wait for print to complete
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Serial.end(); //Disable Serial
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am_hal_sysctrl_sleep(AM_HAL_SYSCTRL_SLEEP_DEEP);
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//We should never get here.
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}
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void loop()
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{
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//Do nothing
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}

‎libraries/Examples/examples/Advanced/LowPower_WithWake/LowPower_WithWake.ino

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/*
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Artemis Low Power: How low can we go?
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By: Nathan Seidle
4+
SparkFun Electronics
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Date: October 17th, 2019
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License: This code is public domain. Based on deepsleep_wake.c from Ambiq SDK v2.2.0.
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A big thanks to robin_hodgson for pointing out the HFRC shutdown requirement and
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turning off the SWD pins.
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SparkFun labored with love to create this code. Feel like supporting open source hardware?
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Buy a board from SparkFun! https://www.sparkfun.com/products/15376
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How close can we get to 2.7uA in deep sleep?
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This example shows how decrease the Artemis current consumption to ~2.4uA in deep sleep
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with a wake up every 5 seconds to blink the LED. The RTC is used to trigger an interrupt
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every second.
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Note that Artemis modules with revision A1 silicon will use ~30uA. Please see the
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Ambiq errata for more information: https://www.ambiqmicro.com/static/mcu/files/Apollo3_Blue_Errata_List_v1_0_external_release.pdf
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To monitor the current to the Edge cut the MEAS jumper, solder in headers, and attach
22+
a DMM via IC hooks (https://www.sparkfun.com/products/506).
23+
24+
The USB to serial bridge draws some current:
25+
Serial Basic C - ~1.2uA (https://www.sparkfun.com/products/15096)
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FTDI Basic - ~5.5uA (https://www.sparkfun.com/products/9873)
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*/
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static uint32_t g_RTCseconds = 0;
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void setup()
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{
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Serial.begin(115200);
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Serial.println("Low power sleep example");
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pinMode(LED_BUILTIN, OUTPUT);
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//Turn off ADC
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power_adc_disable();
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// Set the clock frequency.
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am_hal_clkgen_control(AM_HAL_CLKGEN_CONTROL_SYSCLK_MAX, 0);
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// Set the default cache configuration
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am_hal_cachectrl_config(&am_hal_cachectrl_defaults);
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am_hal_cachectrl_enable();
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// Initialize for low power in the power control block
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am_hal_pwrctrl_low_power_init();
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// Disabling the debugger GPIOs saves about 1.2 uA total:
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am_hal_gpio_pinconfig(20 /* SWDCLK */, g_AM_HAL_GPIO_DISABLE);
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am_hal_gpio_pinconfig(21 /* SWDIO */, g_AM_HAL_GPIO_DISABLE);
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// These two GPIOs are critical: the TX/RX connections between the Artemis module and the CH340S on the Blackboard
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// are prone to backfeeding each other. To stop this from happening, we must reconfigure those pins as GPIOs
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// and then disable them completely:
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am_hal_gpio_pinconfig(48 /* TXO-0 */, g_AM_HAL_GPIO_DISABLE);
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am_hal_gpio_pinconfig(49 /* RXI-0 */, g_AM_HAL_GPIO_DISABLE);
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// The default Arduino environment runs the System Timer (STIMER) off the 48 MHZ HFRC clock source.
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// The HFRC appears to take over 60 uA when it is running, so this is a big source of extra
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// current consumption in deep sleep.
65+
// For systems that might want to use the STIMER to generate a periodic wakeup, it needs to be left running.
66+
// However, it does not have to run at 48 MHz. If we reconfigure STIMER (system timer) to use the 32768 Hz
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// XTAL clock source instead the measured deepsleep power drops by about 64 uA.
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am_hal_stimer_config(AM_HAL_STIMER_CFG_CLEAR | AM_HAL_STIMER_CFG_FREEZE);
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// This option selects 32768 Hz via crystal osc. This appears to cost about 0.1 uA versus selecting "no clock"
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am_hal_stimer_config(AM_HAL_STIMER_XTAL_32KHZ);
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// This option would be available to systems that don't care about passing time, but might be set
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// to wake up on a GPIO transition interrupt.
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//am_hal_stimer_config(AM_HAL_STIMER_NO_CLK);
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//Turn OFF Flash1
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if (am_hal_pwrctrl_memory_enable(AM_HAL_PWRCTRL_MEM_FLASH_512K))
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{
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while (1)
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;
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}
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// Power down SRAM
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PWRCTRL->MEMPWDINSLEEP_b.SRAMPWDSLP = PWRCTRL_MEMPWDINSLEEP_SRAMPWDSLP_ALLBUTLOWER32K;
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setupRTC();
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Serial.println("Going to sleep...");
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delay(100); //Wait for print to complete
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Serial.end(); //Disable Serial
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// Enable interrupts to the core.
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am_hal_interrupt_master_enable();
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}
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void loop()
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{
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// Go to Deep Sleep.
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am_hal_sysctrl_sleep(AM_HAL_SYSCTRL_SLEEP_DEEP);
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}
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void setupRTC()
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{
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// Enable the XT for the RTC.
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am_hal_clkgen_control(AM_HAL_CLKGEN_CONTROL_XTAL_START, 0);
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// Select XT for RTC clock source
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am_hal_rtc_osc_select(AM_HAL_RTC_OSC_XT);
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// Enable the RTC.
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am_hal_rtc_osc_enable();
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// Set the alarm repeat interval to be every second.
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am_hal_rtc_alarm_interval_set(AM_HAL_RTC_ALM_RPT_SEC);
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// Clear the RTC alarm interrupt.
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am_hal_rtc_int_clear(AM_HAL_RTC_INT_ALM);
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// Enable the RTC alarm interrupt.
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am_hal_rtc_int_enable(AM_HAL_RTC_INT_ALM);
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// Enable RTC interrupts to the NVIC.
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NVIC_EnableIRQ(RTC_IRQn);
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}
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extern "C" void am_rtc_isr(void)
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{
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// Clear the RTC alarm interrupt.
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am_hal_rtc_int_clear(AM_HAL_RTC_INT_ALM);
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// Check the desired number of seconds until LED is toggled.
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if (++g_RTCseconds >= 5)
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{
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// Reset the seconds counter.
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g_RTCseconds = 0;
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// Toggle LED
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digitalWrite(LED_BUILTIN, HIGH);
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delay(100);
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digitalWrite(LED_BUILTIN, LOW);
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}
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}

‎variants/SparkFun_Edge2/config/variant.cpp

+2-2
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@@ -24,7 +24,7 @@ SOFTWARE.
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// Apollo3 pads 30 and 46 are not exposed by Artemis module
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const ap3_gpio_pad_t ap3_variant_pinmap[AP3_VARIANT_NUM_PINS] = {
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AP3_GPIO_PAD_UNUSED,
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0, //Mic VDD
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AP3_GPIO_PAD_UNUSED,
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AP3_GPIO_PAD_UNUSED,
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AP3_GPIO_PAD_UNUSED,
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AP3_GPIO_PAD_UNUSED,
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39, //Qwiic SCL
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40, //Qwiic SDA
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AP3_GPIO_PAD_UNUSED,
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41, //Accel VDD
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42, //Accel SCL
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43, //Accel SDA
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44, //GPIO 44

‎variants/SparkFun_Edge2/config/variant.h

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@@ -57,4 +57,8 @@ extern Uart Serial;
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#define MIC_DATA 29
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#define MIC_CLOCK 12
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#define MIC_VDD 0
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#define ACCEL_VDD 41
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#define CAMERA_VDD 32
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#endif // _AP3_VARIANT_H_

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