LP core was unable to boot when system was in deepsleep.
This was due to lp uart init in LP rom using XTAL as clk source,
which is normally powered down during sleep.
This would cause lp uart to get stuck while printing ROM output,
and the app would never boot.
Also fixed wrong wakeup cause used by HP core for ULP wake up
When using USB-serial-jtag for monitoring idf-monitor will lose connection
during deep sleep (because the peripheral powers down) and will need
some time to reconnect when we wake-up. In the ULP examples this would result in
the chip waking up->printing-> going back to sleep, before idf-monitor is even able
to connect, and users would erroneously assume the chip never woke up.
Add a 1 sec delay at the start of the examples to improve the user experience when
using jtag-serial.
This commit adds a minimal logging driver for the LP core. The logging
driver provides a printf function which is built on top of the LP UART
driver. The commit also adds an example to demonstrate how to use print
statements in an LP core program.
This commit adds a UART driver for the LP core to interact with the LP
UART. The commit also adds an example to demonstrate the usage of the LP
UART driver.
