ESP32: Attaching an interrupt directly to system time - c++

Question

Currently I'm setting a separate hardware timer to the system time periodically to trigger timed interrupts. It's working fine but for elegance sake, but I wondered if it was possible to attach an interrupt directly to the system time
The events are pretty fast: one every 260 microseconds
ESP32 has a few clocks used for system time. The default full power clock is an 80 MHz called APB_CLK. But even the slow RTC clock has 6.6667 μs resolution. (Documentation here: https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/system/system_time.html)
I have a GPS module that I use to update the system time periodically using adjtime(3). The advantage of that being that it gradually adjusts the system time monotonically. Also system time calls are thread safe
I'm using the Arduino IDE, so my knowledge of accessing registers and interrupts directly is poor. Here's a semi boiled down version of what I'm doing. Bit banging a synchronized digital signal. Rotating in 160 bit pages that are prepped from the other core. It's not all of my code, so something not important might be missing:
#define CPU_SPEED 40
hw_timer_t* timer = NULL;
PageData pages[2];
PageData* timerCurrentPage = &pages[0];
PageData* loopCurrentPage = &pages[1];
TaskHandle_t prepTaskHandle;
volatile int bitCount = 0;
void IRAM_ATTR onTimer() {
int level = timerCurrentPage->data[bitCount];
dac_output_voltage(DAC_CHANNEL_1, level?high:low);
bitCount++;
if(bitCount<160) {
timerAlarmWrite(timer, (timerCurrentPage->startTick+timerCurrentPage->ticksPerPage*bitCount), false);
} else {
if(timerCurrentPage == &pages[0]) timerCurrentPage = &pages[1];
else timerCurrentPage = &pages[0];
bitCount = 0;
timerAlarmWrite(timer, (timerCurrentPage->startTick), false);
vTaskResume(prepTaskHandle);
}
}
uint64_t nowTick() {
timeval timeStruct;
gettimeofday(&timeStruct, NULL);
uint64_t result = (uint64_t)timeStruct.tv_sec*1000000UL + (uint64_t)timeStruct.tv_usec;
return result;
}
void gpsUpdate(uint64_t micros) {
int64_t now = nowTick();
int64_t offset = micros - now;
timeval adjustStruct = {0,offset};
adjtime(&adjustStruct,NULL);
}
void setup() {
setCpuFrequencyMhz(CPU_SPEED);
timer = timerBegin(0, CPU_SPEED, true);
timerWrite(timer, nowTick());
timerAttachInterrupt(timer, &onTimer, true);
setPage(&pages[0]);
xTaskCreatePinnedToCore(
prepLoop, /* Task function. */
"Prep Task", /* name of task. */
10000, /* Stack size of task */
NULL, /* parameter of the task */
1, /* priority of the task */
&prepTaskHandle, /* Task handle to keep track of created task */
1); /* pin task to core 0 */
timerAlarmWrite(timer, (timerCurrentPage->startTick), false);
}
//On Core 1
void prepLoop() {
while(1) {
vTaskSuspend(NULL); //prepTaskHandle
timerWrite(timer, nowTick());
if(loopCurrentPage == &pages[0]) loopCurrentPage = &pages[1];
else loopCurrentPage = &pages[0];
setPage(loopCurrentPage);
}
}