handle tinyusb device tasks on a timer, allows delays in app

2 files changed, 38 insertions, 8 deletions

diff --git a/watch-library/main.c b/watch-library/main.c
index 886ab851..3133c2d2 100755
--- a/watch-library/main.c
+++ b/watch-library/main.c
@@ -58,11 +58,8 @@ int main(void) {
     // check if we are plugged into USB power.
     watch_enable_digital_input(VBUS_DET);
     watch_enable_pull_down(VBUS_DET);
-    // IF WE ARE:
     if (watch_get_pin_level(VBUS_DET)) {
-        // Ramp up to 16 MHz (seems necessary for USB to work)...
-        hri_oscctrl_write_OSC16MCTRL_reg(OSCCTRL, OSCCTRL_OSC16MCTRL_ONDEMAND | OSCCTRL_OSC16MCTRL_FSEL_16 | OSCCTRL_OSC16MCTRL_ENABLE);
-        // ...and enable USB functionality.
+        // if so, enable USB functionality.
         _watch_enable_usb();
     }
     watch_disable_digital_input(VBUS_DET);
@@ -71,11 +68,10 @@ int main(void) {
     app_setup();
 
     while (1) {
+        bool usb_enabled = hri_usbdevice_get_CTRLA_ENABLE_bit(USB);
         bool can_sleep = app_loop();
-        if (hri_usbdevice_get_CTRLA_ENABLE_bit(USB)) {
-            // if USB is enabled, do not sleep, and handle any pending TinyUSB tasks.
-            tud_task();
-        } else if (can_sleep) {
+
+        if (can_sleep && !usb_enabled) {
             app_prepare_for_sleep();
             sleep(4);
             app_wake_from_sleep();
diff --git a/watch-library/watch/watch_private.c b/watch-library/watch/watch_private.c
index 550419a2..ab988d10 100644
--- a/watch-library/watch/watch_private.c
+++ b/watch-library/watch/watch_private.c
@@ -49,6 +49,11 @@ void _watch_enable_usb() {
     // disable USB, just in case.
     hri_usb_clear_CTRLA_ENABLE_bit(USB);
 
+    // Ramp up to 16 MHz (seems necessary for USB to work)...
+    hri_oscctrl_write_OSC16MCTRL_reg(OSCCTRL, OSCCTRL_OSC16MCTRL_ONDEMAND | OSCCTRL_OSC16MCTRL_FSEL_16 | OSCCTRL_OSC16MCTRL_ENABLE);
+    // ...and wait for it to be ready.
+    while (!hri_oscctrl_get_STATUS_OSC16MRDY_bit(OSCCTRL));
+
     // reset flags and disable DFLL
     OSCCTRL->INTFLAG.reg = OSCCTRL_INTFLAG_DFLLRDY;
     OSCCTRL->DFLLCTRL.reg = 0;
@@ -86,7 +91,31 @@ void _watch_enable_usb() {
     gpio_set_pin_function(PIN_PA24, PINMUX_PA24G_USB_DM);
     gpio_set_pin_function(PIN_PA25, PINMUX_PA25G_USB_DP);
 
+    // before we init TinyUSB, we are going to need a periodic callback to handle TinyUSB tasks.
+    // TC2 and TC3 are reserved for devices on the 9-pin connector, so let's use TC0.
+    // clock TC0 with the 16 MHz clock on GCLK0.
+    hri_gclk_write_PCHCTRL_reg(GCLK, TC0_GCLK_ID, GCLK_PCHCTRL_GEN_GCLK0_Val | GCLK_PCHCTRL_CHEN);
+    // and enable the peripheral clock.
+    hri_mclk_set_APBCMASK_TC0_bit(MCLK);
+    // disable and reset TC0.
+    hri_tc_clear_CTRLA_ENABLE_bit(TC0);
+    hri_tc_wait_for_sync(TC0, TC_SYNCBUSY_ENABLE);
+    hri_tc_write_CTRLA_reg(TC0, TC_CTRLA_SWRST);
+    hri_tc_wait_for_sync(TC0, TC_SYNCBUSY_SWRST);
+    // configure the TC to overflow 1,000 times per second
+    hri_tc_write_CTRLA_reg(TC0, TC_CTRLA_PRESCALER_DIV64 |  // divide the clock by 64 to count at 250000 KHz
+                                TC_CTRLA_MODE_COUNT8 |      // count in 8-bit mode
+                                TC_CTRLA_RUNSTDBY);         // run in standby, just in case we figure that out
+    hri_tccount8_write_PER_reg(TC0, 250);                   // 250000 KHz / 250 = 1,000 Hz
+    // set an interrupt on overflow; this will call TC0_Handler below.
+    hri_tc_set_INTEN_OVF_bit(TC0);
+    NVIC_ClearPendingIRQ(TC0_IRQn);
+    NVIC_EnableIRQ (TC0_IRQn);
+
+    // now we can init TinyUSB
     tusb_init();
+    // and start the timer that handles USB device tasks.
+    hri_tc_set_CTRLA_ENABLE_bit(TC0);
 }
 
 // this function ends up getting called by printf to log stuff to the USB console.
@@ -119,6 +148,11 @@ void USB_Handler(void) {
     tud_int_handler(0);
 }
 
+void TC0_Handler(void) {
+    tud_task();
+    TC0->COUNT8.INTFLAG.reg |= TC_INTFLAG_OVF;
+}
+
 
 // USB Descriptors and tinyUSB callbacks follow.