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

deniscollis — Thu, 17 Feb 2022 19:52:30 GMT

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

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

deniscollis — Fri, 18 Feb 2022 20:20:17 GMT

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.

Kinetis MicrocontrollersのトピックRe: Divided RTC to drive 120Hz display while MCU in low power or stop mode

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

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