Good day
I am using Embedded Artists' RT1176 uCOM and their adaptation of NXP's RT1176 v2.9.2 SDK.
After many days of testing, we discovered that there is a bug in BOARD_SystickElapsedTicks(). This bug causes the function to occasionally return a very large (and incorrect) 'elapsed' value. A screenshot of the SDK's function is shown below:
When an overflow of the Systick counter occurs, Systick_Handler() executes, and increases g_ovf_counter. Typically, if this occurred before BOARD_SystickElapsedTicks() was called, then the first 'elapsed' var calculation would have a large negative number as a result. The second 'elapsed' var calculation would then add a larger number to 'elapsed', resulting in a positive number.
However, if this overflow occurred between these two calculations, then the first line would give 'elapsed' a positive number, and the second line would add a large positive offset. This would cause 'elapsed' to have a much larger value than it should, for only one call to BOARD_SystickElapsedTicks().
To fix this, we added a do-while() to check if an overflow has occurred during the ‘elapsed’ calculations. If so, we redo the calculations to ensure that the ‘elapsed’ value is correct.
The fixed BOARD_SystickElapsedTicks() can be seen below:
I am posting this in the hope that NXP will fix their SDK as soon as possible.
In the mean time, I hope that this helps someone, because NXP could be a while...
Hi，
Assume the elapsed time period: time_1 is from the time point of calling BOARD_SystickStart to the BOARD_SystickElapsedTicks(), according to your modified code, if an overflow occurs between these two calculations, the elapsed time period will extend just as the below figure shows, because the systick is always working.
// ARM-core specific function to compute the elapsed systick timer ticks.
int32_t BOARD_SystickElapsedTicks(int32_t *pStart)
{
int32_t elapsed;
int32_t curr_val = SYST_CVR & 0x00FFFFFF;
int32_t rounded_over = g_ovf_counter - g_ovf_stamp;
elapsed= SYST_RVR * rounded_over+*pStart-curr_val;
return elapsed;
}
So I'd like to suggest you can use the below code to optimize the function.
Have a great day,
TIC
-------------------------------------------------------------------------------
Note:
- If this post answers your question, please click the "Mark Correct" button. Thank you!
- We are following threads for 7 weeks after the last post, later replies are ignored
Please open a new thread and refer to the closed one, if you have a related question at a later point in time.
-------------------------------------------------------------------------------))
