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+# dwt_delay
+Microseconds delay lib based on DWT for STM32 or whatever ARM supporting it. 
+Just include `dwt_delay.h` in your project, call `DWT_Init()` and then use delays as needed.
+
+Depending on MCU used, you may need to include another header file (with MCU peripherals defines) in `dwt_delay.h`.
+The `stm32f1xx.h` is included by default, allowing STM32F1xx to start out of the box.
+If you don't use STM32 MCU or CubeMX, read a section at the end.  
+
+Functions are named as DWT_* to be HAL-alike. Feel free to do whatever you like with this lib,
+change names, indents, coding style, use it in LHC firmware.
+
+
+## Example
+
+```c
+/* main.c */
+
+#include "dwt_delay.h"
+
+
+void main (void)
+{
+    // Init section of your code
+    DWT_Init();
+
+
+    while(1) {
+        // Delay for 42us
+        DWT_Delay(42);
+    }
+
+}
+```
+
+## Notes on Cortex-M0/0+/1
+Unfortunately, these are not supported, since cores have no access to DWT. CMSIS library states:
+```
+Cortex-M0/0+/1 Core Debug Registers are only accessible over DAP and not via processor
+``` 
+You may want a delay function based on hardware timer instead.
+
+
+## What about Cortex-M35/55/85?
+I don't have any of these to check, but in theory they are supported.
+Anyway you have to change `CoreDebug` to `DCB`, because `CoreDebug` is deprecated in these cores.
+
+Hence, init sequence should be something like:
+```c
+DCB->DEMCR |= ‎DCB_DEMCR_TRCENA_Msk;
+``` 
+
+
+## I'm not with STM but need microsec delays
+There's an option to try! Also suits those, who use STM32, but dont use HAL/LL libs.
+
+Include a CMSIS header file according to your core in `dwt_delay.c` and change `SystemCoreClock`
+variable to whatever you probably have in the project representing clock frequency (in Hz).
+
+Something like this:
+```c
+// In dwt_delay.c
+
+#include "dwt_delay.h"
+#include "core_cm4.h"                   // CMSIS header
+
+#define SystemCoreClock   NameOfTheGlobalVariableInYourProject_or_AnotherDefine
+// or at least
+#define SystemCoreClock   48000000UL    // Clock is 48Mhz
+...
+``` 
+
+
+## Changelog
+- **2018-01-06**
+This lib emerged.
+
+- **2019-02-19**
+Overflow check added.
+
+- **2019-03-26**
+Typo in definition fixed. Got back to short and simpler function.
+
+- **2023-11-21**
+Now it is MIT License. Added warning for Cortex-M0/0+/1 and notes regarding other Cortex-M cores.