In RT/NIL 3.0 the systick is generated from a configurable timer.
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/*
* ST driver system settings.
*/
#define STM32_ST_IRQ_PRIORITY 2
#define STM32_ST_USE_TIMER 3
with definitions like
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/**
* @brief System time counter resolution.
* @note Allowed values are 16 or 32 bits.
*/
#define NIL_CFG_ST_RESOLUTION 16
setting the timer resolution.
Is there a specific reason why it is not possible to use the 24-bit Cortex-M SysTick timer (see http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0552a/Babieigh.html) as in ChibiOS 2.x (i think)? The F030, F042 and L151 devices I'm currently using do not have any 32-bit timers. This means that I either have to set the systick frequency very low (which limits achievable delay resolution) or the maximum allowable delay is limited (disregarding tricks like splitting it into multiple delays etc).
Please note that I currently do not have any particular application for using the SysTick timer, but I'd like to know if there are any conceptual issues so I can implement & contribute it when I need it.
Best regards, Uli
