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fix(lis2dw): Re-initialize accelerometer after waking from sleep (#16)

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* fix(lis2dw): Re-initialize accelerometer after waking from sleep

The LIS2DW accelerometer was not being re-initialized correctly after the device woke from sleep mode. When entering sleep, `watch_enter_sleep_mode` disables peripherals and pins, including those for I²C, to conserve power.

Upon waking, the `app_setup` function was designed to re-initialize the hardware. However, the logic only performed the I²C device check once on the initial boot. On subsequent wakes, the `movement_state.has_lis2dw` flag would prevent the I²C bus and the LIS2DW driver from being set up again. This caused any watch face functionality that relied on the accelerometer, such as the countdown face's tap detection, to fail after a sleep/wake cycle.

This commit refactors the initialization logic within `app_setup`. It now uses a static boolean `lis2dw_initialized` to ensure the sensor is detected only once at boot time. On subsequent wakes, if the sensor was originally found to be present, the I²C bus is explicitly re-enabled and the driver is re-initialized with `lis2dw_begin()` before its configuration is reapplied. This ensures the accelerometer is reliably available after every wake-up.

* fix(lis2dw): only check for accelerometer presence once per boot

Previously, devices without the LIS2DW sensor would re-enable I2C and attempt to detect the sensor on every wake from sleep, wasting power and CPU cycles. This change introduces a static `lis2dw_checked` flag that is set after the first detection attempt, regardless of whether the sensor is found. Now, the presence check and I2C enable/disable only occur once per boot, ensuring that devices without the sensor do not repeatedly attempt detection, improving efficiency and battery life.
This commit is contained in:
Daniel Bergman 2025-06-25 15:18:33 +02:00 committed by GitHub
parent 918549a462
commit 7f9a00ef35
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GPG Key ID: B5690EEEBB952194
1 changed files with 48 additions and 41 deletions
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movement.c
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@ -716,53 +716,60 @@ void app_setup(void) {
watch_register_interrupt_callback(HAL_GPIO_BTN_ALARM_pin(), cb_alarm_btn_interrupt, INTERRUPT_TRIGGER_BOTH);
#ifdef I2C_SERCOM
// if accelerometer was already detected and set up, no need to set it up again.
if (!movement_state.has_lis2dw) {
static bool lis2dw_checked = false;
if (!lis2dw_checked) {
watch_enable_i2c();
if (lis2dw_begin()) {
movement_state.has_lis2dw = true;
lis2dw_set_mode(LIS2DW_MODE_LOW_POWER); // select low power (not high performance) mode
lis2dw_set_low_power_mode(LIS2DW_LP_MODE_1); // lowest power mode, 12-bit
lis2dw_set_low_noise_mode(false); // low noise mode raises power consumption slightly; we don't need it
lis2dw_enable_stationary_motion_detection(); // stationary/motion detection mode keeps the data rate at 1.6 Hz even in sleep
lis2dw_set_range(LIS2DW_RANGE_2_G); // Application note AN5038 recommends 2g range
lis2dw_enable_sleep(); // allow acceleromter to sleep and wake on activity
lis2dw_configure_wakeup_threshold(32); // g threshold to wake up: (THS * FS / 64) where FS is "full scale" of ±2g.
lis2dw_configure_6d_threshold(3); // 0-3 is 80, 70, 60, or 50 degrees. 50 is least precise, hopefully most sensitive?
// set up interrupts:
// INT1 is wired to pin A3. We'll configure the accelerometer to output an interrupt on INT1 when it detects an orientation change.
/// TODO: We had routed this interrupt to TC2 to count orientation changes, but TC2 consumed too much power.
/// Orientation changes helped with sleep tracking; would love to bring this back if we can find a low power solution.
/// For now, commenting these lines out; check commit 27f0c629d865f4bc56bc6e678da1eb8f4b919093 for power-hungry but working code.
// lis2dw_configure_int1(LIS2DW_CTRL4_INT1_6D);
// HAL_GPIO_A3_in();
// next: INT2 is wired to pin A4. We'll configure the accelerometer to output the sleep state on INT2.
// a falling edge on INT2 indicates the accelerometer has woken up.
lis2dw_configure_int2(LIS2DW_CTRL5_INT2_SLEEP_STATE | LIS2DW_CTRL5_INT2_SLEEP_CHG);
HAL_GPIO_A4_in();
// Wake on motion seemed like a good idea when the threshold was lower, but the UX makes less sense now.
// Still if you want to wake on motion, you can do it by uncommenting this line:
// watch_register_extwake_callback(HAL_GPIO_A4_pin(), cb_accelerometer_wake, false);
// later on, we are going to use INT1 for tap detection. We'll set up that interrupt here,
// but it will only fire once tap recognition is enabled.
watch_register_interrupt_callback(HAL_GPIO_A3_pin(), cb_accelerometer_event, INTERRUPT_TRIGGER_RISING);
// Enable the interrupts...
lis2dw_enable_interrupts();
// ...and power down the accelerometer to save energy. This means the interrupts we just configured won't fire.
// Tap detection will ramp up sesing and make use of the A3 interrupt.
// If a watch face wants to check in on the A4 pin, it can call movement_set_accelerometer_background_rate
lis2dw_set_data_rate(LIS2DW_DATA_RATE_POWERDOWN);
movement_state.accelerometer_background_rate = LIS2DW_DATA_RATE_POWERDOWN;
} else {
movement_state.has_lis2dw = false;
watch_disable_i2c();
}
lis2dw_checked = true;
} else if (movement_state.has_lis2dw) {
watch_enable_i2c();
lis2dw_begin();
}
if (movement_state.has_lis2dw) {
lis2dw_set_mode(LIS2DW_MODE_LOW_POWER); // select low power (not high performance) mode
lis2dw_set_low_power_mode(LIS2DW_LP_MODE_1); // lowest power mode, 12-bit
lis2dw_set_low_noise_mode(false); // low noise mode raises power consumption slightly; we don't need it
lis2dw_enable_stationary_motion_detection(); // stationary/motion detection mode keeps the data rate at 1.6 Hz even in sleep
lis2dw_set_range(LIS2DW_RANGE_2_G); // Application note AN5038 recommends 2g range
lis2dw_enable_sleep(); // allow acceleromter to sleep and wake on activity
lis2dw_configure_wakeup_threshold(32); // g threshold to wake up: (THS * FS / 64) where FS is "full scale" of ±2g.
lis2dw_configure_6d_threshold(3); // 0-3 is 80, 70, 60, or 50 degrees. 50 is least precise, hopefully most sensitive?
// set up interrupts:
// INT1 is wired to pin A3. We'll configure the accelerometer to output an interrupt on INT1 when it detects an orientation change.
/// TODO: We had routed this interrupt to TC2 to count orientation changes, but TC2 consumed too much power.
/// Orientation changes helped with sleep tracking; would love to bring this back if we can find a low power solution.
/// For now, commenting these lines out; check commit 27f0c629d865f4bc56bc6e678da1eb8f4b919093 for power-hungry but working code.
// lis2dw_configure_int1(LIS2DW_CTRL4_INT1_6D);
// HAL_GPIO_A3_in();
// next: INT2 is wired to pin A4. We'll configure the accelerometer to output the sleep state on INT2.
// a falling edge on INT2 indicates the accelerometer has woken up.
lis2dw_configure_int2(LIS2DW_CTRL5_INT2_SLEEP_STATE | LIS2DW_CTRL5_INT2_SLEEP_CHG);
HAL_GPIO_A4_in();
// Wake on motion seemed like a good idea when the threshold was lower, but the UX makes less sense now.
// Still if you want to wake on motion, you can do it by uncommenting this line:
// watch_register_extwake_callback(HAL_GPIO_A4_pin(), cb_accelerometer_wake, false);
// later on, we are going to use INT1 for tap detection. We'll set up that interrupt here,
// but it will only fire once tap recognition is enabled.
watch_register_interrupt_callback(HAL_GPIO_A3_pin(), cb_accelerometer_event, INTERRUPT_TRIGGER_RISING);
// Enable the interrupts...
lis2dw_enable_interrupts();
// ...and power down the accelerometer to save energy. This means the interrupts we just configured won't fire.
// Tap detection will ramp up sesing and make use of the A3 interrupt.
// If a watch face wants to check in on the A4 pin, it can call movement_set_accelerometer_background_rate
lis2dw_set_data_rate(LIS2DW_DATA_RATE_POWERDOWN);
movement_state.accelerometer_background_rate = LIS2DW_DATA_RATE_POWERDOWN;
}
#endif