run watch at 4 MHz unless USB is enabled

4 files changed, 17 insertions, 6 deletions

diff --git a/watch-library/config/hpl_oscctrl_config.h b/watch-library/config/hpl_oscctrl_config.h
index 405ff207..ba2d42e6 100644
--- a/watch-library/config/hpl_oscctrl_config.h
+++ b/watch-library/config/hpl_oscctrl_config.h
@@ -147,7 +147,7 @@
 // <i> This defines the oscillator frequency (Mhz)
 // <id> osc16m_freq
 #ifndef CONF_OSC16M_FSEL
-#define CONF_OSC16M_FSEL OSCCTRL_OSC16MCTRL_FSEL_8_Val
+#define CONF_OSC16M_FSEL OSCCTRL_OSC16MCTRL_FSEL_4_Val
 #endif
 
 // <q> Oscillator Calibration Control
diff --git a/watch-library/config/peripheral_clk_config.h b/watch-library/config/peripheral_clk_config.h
index 5cd1bb68..61619b6a 100644
--- a/watch-library/config/peripheral_clk_config.h
+++ b/watch-library/config/peripheral_clk_config.h
@@ -61,7 +61,7 @@
  * \brief CPU's Clock frequency
  */
 #ifndef CONF_CPU_FREQUENCY
-#define CONF_CPU_FREQUENCY 8000000
+#define CONF_CPU_FREQUENCY 4000000
 #endif
 
 // <y> RTC Clock Source
diff --git a/watch-library/hpl/core/hpl_core_m0plus_base.c b/watch-library/hpl/core/hpl_core_m0plus_base.c
index 1d32300a..cad2a662 100644
--- a/watch-library/hpl/core/hpl_core_m0plus_base.c
+++ b/watch-library/hpl/core/hpl_core_m0plus_base.c
@@ -167,7 +167,8 @@ static inline uint32_t _get_cycles_for_us_internal(const uint16_t us, const uint
  */
 uint32_t _get_cycles_for_us(const uint16_t us)
 {
-	return _get_cycles_for_us_internal(us, CONF_CPU_FREQUENCY, CPU_FREQ_POWER);
+	int32_t freq = hri_usbdevice_get_CTRLA_ENABLE_bit(USB) ? 8000000 : 4000000;
+	return _get_cycles_for_us_internal(us, freq, CPU_FREQ_POWER);
 }
 
 /**
@@ -196,5 +197,6 @@ static inline uint32_t _get_cycles_for_ms_internal(const uint16_t ms, const uint
  */
 uint32_t _get_cycles_for_ms(const uint16_t ms)
 {
-	return _get_cycles_for_ms_internal(ms, CONF_CPU_FREQUENCY, CPU_FREQ_POWER);
+	int32_t freq = hri_usbdevice_get_CTRLA_ENABLE_bit(USB) ? 8000000 : 4000000;
+	return _get_cycles_for_ms_internal(ms, freq, CPU_FREQ_POWER);
 }
diff --git a/watch-library/watch/watch_private.c b/watch-library/watch/watch_private.c
index a4e2f72c..88d80be9 100644
--- a/watch-library/watch/watch_private.c
+++ b/watch-library/watch/watch_private.c
@@ -54,8 +54,14 @@ void _watch_enable_tcc() {
     hri_tcc_wait_for_sync(TCC0, TCC_SYNCBUSY_ENABLE);
     hri_tcc_write_CTRLA_reg(TCC0, TCC_CTRLA_SWRST);
     hri_tcc_wait_for_sync(TCC0, TCC_SYNCBUSY_SWRST);
-    // have prescaler divide our 8 MHz clock down to 1 MHz.
-    hri_tcc_write_CTRLA_reg(TCC0, TCC_CTRLA_PRESCALER_DIV8);
+    // divide the clock down to 1 MHz
+    if (hri_usbdevice_get_CTRLA_ENABLE_bit(USB)) {
+        // if USB is enabled, we are running an 8 MHz clock.
+        hri_tcc_write_CTRLA_reg(TCC0, TCC_CTRLA_PRESCALER_DIV8);
+    } else {
+        // otherwise it's 4 Mhz.
+        hri_tcc_write_CTRLA_reg(TCC0, TCC_CTRLA_PRESCALER_DIV4);
+    }
     // We're going to use normal PWM mode, which means period is controlled by PER, and duty cycle is controlled by
     // each compare channel's value:
     //  * Buzzer tones are set by setting PER to the desired period for a given frequency, and CC[1] to half of that
@@ -98,6 +104,9 @@ void _watch_enable_usb() {
     // disable USB, just in case.
     hri_usb_clear_CTRLA_ENABLE_bit(USB);
 
+    // bump clock up to 8 MHz
+    hri_oscctrl_write_OSC16MCTRL_FSEL_bf(OSCCTRL, OSCCTRL_OSC16MCTRL_FSEL_8_Val);
+
     // reset flags and disable DFLL
     OSCCTRL->INTFLAG.reg = OSCCTRL_INTFLAG_DFLLRDY;
     OSCCTRL->DFLLCTRL.reg = 0;