Switched from usb-stack assisted SOF measurement to pure software solution to keep API compatibility to the original tinyusb

stm32/aioc-fw/Src/usb.c

@@ -7,7 +7,8 @@
 
 // We have ISOCHRONOUS endpoints defined that share the same endpoint number, but have opposing directions.
 // However with STM32 hardware, ISOCHRONOUS endpoints use both RX and TX structures of the same endpoint register in hardware
-// We circumvent a clash by defining our own custom endpoint map for the tiny usb stack
+// We circumvent a clash by defining our own custom endpoint map for the tiny usb stack.
+// This callback is probably not needed with new versions of tinyusb
 uint8_t tu_stm32_edpt_number_cb(uint8_t addr)
 {
     switch (addr) {
@@ -38,12 +39,6 @@ uint8_t tu_stm32_edpt_number_cb(uint8_t addr)
     }
 }
 
-void tu_stm32_sof_cb(void)
-{
-    /* Capture timer value */
-    USB_SOF_TIMER->EGR = TIM_EGR_CC1G;
-}
-
 // FIXME: Do all three need to be handled, or just the LP one?
 // USB high-priority interrupt (Channel 74): Triggered only by a correct
 // transfer event for isochronous and double-buffer bulk transfer to reach

stm32/aioc-fw/Src/usb.h

@@ -5,7 +5,7 @@
 #include "usb_serial.h"
 
 #define USB_SOF_TIMER       TIM2
-#define USB_SOF_TIMER_CCR   TIM2->CCR1
+#define USB_SOF_TIMER_CNT   TIM2->CNT
 #define USB_SOF_TIMER_HZ    72000000UL
 
 void USB_Init(void);

stm32/aioc-fw/Src/usb_audio.c

@@ -581,7 +581,7 @@ void tud_audio_feedback_params_cb(uint8_t func_id, uint8_t alt_itf, audio_feedba
 TU_ATTR_FAST_FUNC void tud_audio_feedback_interval_isr(uint8_t func_id, uint32_t frame_number, uint8_t interval_shift)
 {
     static uint32_t prev_cycles = 0;
-    uint32_t this_cycles = USB_SOF_TIMER_CCR; /* Load from capture register, which is set in tu_stm32_sof_cb */
+    uint32_t this_cycles = USB_SOF_TIMER_CNT;
     uint32_t feedback;
 
     /* Calculate number of master clock cycles between now and last call */