As mentioned in issue #6241 the commit to setup port hooks is now
causing all input/output that are to go to the Mu window to also
go to the LpUart that is defined the port serial.c
and in this case it goes to lpuart4, which on Teensy 4, 4.1 is
used on Arduino Serial2. With this new code this port no longer
works properly.
This is one way to solve it, in that there is a #if defined() that
if not set, all of the code in this file is ignored and the higher
level supervisor stub versions of these functions will be used, which
don't interfere with Serial2 and my test sketch works again.
Note: the PR for Switch to Port Serial Hooks, also changed code in
other ports. I have not tried to see how.
There are other more global fixes for this, in which maybe a higer
level #if that disables the code within the top level supervisor. Or
could be software controlled
Again this may not be the final solution, but at least it gets
Serial2 up and running agin.
I instrumented RTC_Handler and determined that on SAMD51 it was possible
for the interrupt to be delivered well before the actual overflow of the
RTC COUNT register (e.g., a value as small as 0xffff_fffd could be seen
at the time of overflow)
Rather than depending on the overflow interrupt coming in at the same time
as COUNT overflows (exactly), rely only on observed values of COUNT in
_get_count, overflowing when it wraps around from a high value to a low
one.
With this change, PLUS a second change so that it is possible to warp
the RTC counter close to an overflow and test in 20ms instead of 3 days,
there was no problem detected over 20000+ overflows. Before, a substantial
fraction (much greater than 10%) of overflows failed.
Fixes#5985
Change to common-hal/rtc/RTC.c for time warping (plus make rtc_old_count non-static):
```patch
void common_hal_rtc_set_calibration(int calibration) {
+
+ common_hal_mcu_disable_interrupts();
+
+ RTC->MODE0.COUNT.reg = 0xffffff00;
+ rtc_old_count = 0;
+ do {
+ while ((RTC->MODE0.SYNCBUSY.reg & (RTC_MODE0_SYNCBUSY_COUNTSYNC | RTC_MODE0_SYNCBUSY_COUNT)) != 0) { }
+ }
+ while(RTC->MODE0.COUNT.reg < 0xffffff00);
+ common_hal_mcu_enable_interrupts();
+
+ mp_printf(&mp_plat_print, "Warping RTC in calibration setter count=%08x rtc_old_count=%08x\n", RTC->MODE0.COUNT.reg, rtc_old_count);
```
Test program:
```python
import time
from rtc import RTC
i = 0
while True:
RTC().calibration = 1 # Warps to ~16ms before overflow, with patch to RTC code
t0 = time.monotonic_ns()
et = t0 + 20_000_000 # 20ms
while (t1 := time.monotonic_ns()) < et: pass
i += 1
print(f"{i:6d}: duration {t1-t0}")
if t1-t0 > 200_000_000: break
print()
```
To me, it made more sense to track which boards go together in a cluster;
when reviewing a request to actually use a duplicate vid/pid, you want
to know what board(s) it is aliasing.
I also revamped the detection of non-USB boards so that a board .mk file
that couldn't be parsed by the code here would raise a problem instead
of just being skipped for the purposes of checking.
There were some lines with comments on the end, and some variation in
capitalization of the IDs. These are all normalized and a (sometimes
unfriendly!) error printed when it's incorrect.
Before this, here were some ways to trick the duplicate vid/pid checker:
```
USB_PID = 0XABCD
USB_PID = 0xAbCd
USB_PID = 0xABCD # harmless comment?
```
None of these things were ever done on purpose.
