CCmicros - micros version using Cycle countermain
// TODO: this doesn't work for IMXRT - no longer using predefined names | // TODO: this doesn't work for IMXRT - no longer using predefined names | ||||
extern "C" volatile uint32_t systick_millis_count; | extern "C" volatile uint32_t systick_millis_count; | ||||
extern "C" volatile uint32_t systick_cycle_count; | |||||
extern "C" uint32_t systick_safe_read; // micros() synchronization | |||||
extern "C" void systick_isr(void) | extern "C" void systick_isr(void) | ||||
{ | { | ||||
systick_cycle_count = ARM_DWT_CYCCNT; | |||||
systick_millis_count++; | systick_millis_count++; | ||||
MillisTimer::runFromTimer(); | MillisTimer::runFromTimer(); | ||||
} | } |
#include "core_pins.h" | #include "core_pins.h" | ||||
#include "arm_math.h" // micros() synchronization | |||||
//volatile uint32_t F_CPU = 396000000; | //volatile uint32_t F_CPU = 396000000; | ||||
//volatile uint32_t F_BUS = 132000000; | //volatile uint32_t F_BUS = 132000000; | ||||
volatile uint32_t systick_millis_count = 0; | volatile uint32_t systick_millis_count = 0; | ||||
volatile uint32_t systick_cycle_count = 0; | |||||
uint32_t systick_safe_read; // micros() synchronization | |||||
// page 411 says "24 MHz XTALOSC can be the external clock source of SYSTICK" | // page 411 says "24 MHz XTALOSC can be the external clock source of SYSTICK" | ||||
// Testing shows the frequency is actually 100 kHz - but how? Did NXP really | // Testing shows the frequency is actually 100 kHz - but how? Did NXP really | ||||
// TODO... | // TODO... | ||||
} | } | ||||
uint32_t micros(void) | |||||
{ | |||||
uint32_t ccdelta, usec, smc, scc; | |||||
do { | |||||
__LDREXW(&systick_safe_read); | |||||
smc = systick_millis_count; | |||||
scc = systick_cycle_count; | |||||
} while ( __STREXW(1, &systick_safe_read)); | |||||
ccdelta = ARM_DWT_CYCCNT - scc; | |||||
usec = 1000*smc + (ccdelta/(F_CPU_ACTUAL/1000000)); | |||||
return usec; | |||||
} | |||||
#if 0 // kept to compare test to cycle count micro() | |||||
uint32_t micros(void) | uint32_t micros(void) | ||||
{ | { | ||||
uint32_t msec, tick, elapsed, istatus, usec; | uint32_t msec, tick, elapsed, istatus, usec; | ||||
prev_usec = usec; | prev_usec = usec; | ||||
return usec; | return usec; | ||||
} | } | ||||
#endif |
// the ARM clock to run at different speeds. | // the ARM clock to run at different speeds. | ||||
#define SYSTICK_EXT_FREQ 100000 | #define SYSTICK_EXT_FREQ 100000 | ||||
extern volatile uint32_t systick_cycle_count; | |||||
static void configure_systick(void) | static void configure_systick(void) | ||||
{ | { | ||||
_VectorsRam[14] = pendablesrvreq_isr; | _VectorsRam[14] = pendablesrvreq_isr; | ||||
SCB_SHPR3 = 0x20000000; // Systick = priority 32 | SCB_SHPR3 = 0x20000000; // Systick = priority 32 | ||||
ARM_DEMCR |= ARM_DEMCR_TRCENA; | ARM_DEMCR |= ARM_DEMCR_TRCENA; | ||||
ARM_DWT_CTRL |= ARM_DWT_CTRL_CYCCNTENA; // turn on cycle counter | ARM_DWT_CTRL |= ARM_DWT_CTRL_CYCCNTENA; // turn on cycle counter | ||||
systick_cycle_count = ARM_DWT_CYCCNT; // compiled 0, corrected w/1st systick | |||||
} | } | ||||
// R2 | // R2 | ||||
// R1 | // R1 | ||||
// R0 | // R0 | ||||
__attribute__((weak)) | |||||
void unused_interrupt_vector(void) | void unused_interrupt_vector(void) | ||||
{ | { | ||||
// TODO: polling Serial to complete buffered transmits | // TODO: polling Serial to complete buffered transmits |