When no USB host is reading, flushAndWait() spins 50K iterations per
FIFO-full event. With putchar calling WriteByte per byte, the cumulative
delay starves I2C and other peripherals, freezing displays.
Add a txStalled flag: the first FIFO-full triggers one flushAndWait
attempt. If it fails (no host), txStalled is set and all subsequent
writes return immediately with no spin — just a register read and a
bool check. When a host reconnects, SERIAL_IN_EP_DATA_FREE goes back
to 1, bypassing the stall path and clearing the flag automatically.
Replace the busy-wait sleepTicks with an interrupt-driven version that
sets a TIMG0 timer alarm and waits for the interrupt to fire. The timer
alarm handler disables INT_ENA at the peripheral level to prevent
level-triggered re-assertion; sleepTicks re-enables it after each wake.
This avoids burning CPU cycles during time.Sleep and similar delays.
Joel Wetzell
deadprogram
cjpeterson