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
}
We have to read the DR for every byte that we write.
Just reading DR while SPI is busy in a loop can lead to bytes being
left in the fifo, corrupting subsequent reads.
- 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.
