Divided RTC to drive 120Hz display while MCU in low power or stop mode

[deniscollis]

Looking for inspiration...

IoT application. I have a K81/K82 that drives a JDI display.  The display has pixel memory, and so will hold the display image as long as  a nominal 120Hz signal is present on its clock-in pin. Currently the plan is for the display clock to be generated by a FreeRTOS 8ms periodic task pulsing a GPIO pin. I'd like relieve the RTOS of this task, instead driving the 120Hz (or 128Hz, probably) from the TPM.  In addition, I want to clock the TPM from the RTC Oscillator.  This way I hope to stop the K8x core, but leave the TMP peripheral running.

Is this doable?

(The ultimate goal is the minimum energy consumption)

Thanks,
Denis    

[deniscollis · Accepted solution]

Looks like this is not possible with Kinetis. Now opting for the display to have its own clock generator - basically a 32K oscillator and an 8-stage flip-flop. It'll consume 1-2uA, so is within the IoT energy budget.  Downside is that it adds $2 to the per-board cost.