This commit adds the ESP32 vendor libraries for WLAN to the BASELIBS variable. This avoids having to define an additional archive group in the LINKGFLAGS variable which contains these vendor libraries and again RIOT module archive files with the symbols that are refered by these vendor libraries.
Some ESP32 boards (like my SparkFun ESP32 Thing) have a main clock
crystal that runs at 26MHz, not 40MHz. RIOT appears to assume 40MHz.
The mismatch causes the UART to not sync properly, resulting in
garbage written to the terminal instead of log output.
I’ve added:
* A new board configuration constant ESP32_XTAL_FREQ that defaults
to 40, but can be overridden by a board def or at build time to
force a specific value (i.e. 26).
* Some code spliced into system_clk_init() to check this constant and
call rtc_clk_init() to set the correct frequency.
* A copy of the rtf_clk_init() function from the ESP-IDF sources.
Fixes#10272
The problem seemed to be a pipelining problem of write and read instructions when swapping the context. An isync instruction when returning from a context switch solves the potential pipelining problem.
Reason for the problem was that tast_exit function in thread_arch.c tried to release the thread a second time although it was already released in sched_task_exit. A simple check whether the thread is already released (sched_active_thread == NULL) solved the problem.
Xtensa newlib version requires pthread_setcancelstate as symbol. Therefore, the module pthread was always used, which in turn requires the module xtimer. The xtimer module, however, uses TIMER_DEV(0). Therefore, tests/timers failed for TIMER_DEV(0).
