From the ARMv7-M ARM section B3.5.3:
Where there is an overlap between two regions, the register with
the highest region number takes priority.
We want to make sure the mpu_noexec_ram region has the lowest
priority to allow the mpu_stack_guard region to overwrite the first N
bytes of it.
This change fixes using mpu_noexec_ram and mpu_stack_guard together.
cc2538 implements 4 sleep modes.
In the lightest mode (3) any interrupt source can wake up the CPU.
In mode 2, only RTT, GPIO or USB may wake the CPU.
In mode 1 only RTT and GPIO can wake the CPU.
In mode 0 only GPIO can wake the CPU.
In mode 0 and 1 the lower 16k RAM are lost. This is a problem since those
are usually used by RIOT.
The linkerscripts in cc2538/ldscripts take different approaches towards that.
Some only use the upper 16k and leave the other half to be managed by the
application.
`cc2538sf53.ld` which is used by `openmote-b` uses the entire RAM starting
at the lower half, so it will not be able to wake up from those modes.
A quick fix to test those modes with `tests/periph_pm` would be
--- a/cpu/cc2538/ldscripts/cc2538sf53.ld
+++ b/cpu/cc2538/ldscripts/cc2538sf53.ld
@@ -21,7 +21,7 @@ MEMORY
{
rom (rx) : ORIGIN = 0x00200000, LENGTH = 512K - 44
cca : ORIGIN = 0x0027ffd4, LENGTH = 44
- ram (w!rx) : ORIGIN = 0x20000000, LENGTH = 32K
+ ram (w!rx) : ORIGIN = 0x20004000, LENGTH = 16K
}
- cpu/stm32f1: Removed previous code in gpio_init() to provide PB4 on the
Nucleo-F103RB only
- cpu/stm32_common: Introduced STM32F1_DISABLE_JTAG which, if defined in
board.h, exposes the JTAG only pins as GPIOs. This keeps the SWD pins, so that
SWD debugging remains possible
This implements a basic Real Time Clock based on TIM2.
As the timer is too fast and wraps around after just 8 bits, it is
not used directly. Instead TIM2 is responsible for providing a 1 Hz
tick by generating an alarm every second.
The current time data is kept in the `.noinit` section, so it will survive
a reboot, but the clock will not be updated while the bootloader runs, so
expect inaccuracies.
By using a custom EPOCH for the RTC implementation, we can extend the
range of the 32 bit counter based RTC by 118 years.
It also reduces the code size compared to the stdlib based POSIX functions.
