Openmv RT1062 Power Switchiing for Under Power Condition

OpenMV Boards
1

Hi everyone,

I am working on a solar-powered embedded system using the OpenMV RT1062 with a LiFePO4 battery, LTE/GNSS modem, and solar charging setup.

Current setup:

  • 40W solar panel

  • CN3795 MPPT charger

  • 4S LiFePO4 battery

  • LTE/GNSS modem

  • System average load around 1–1.5W

I am facing a power recovery issue during low-battery conditions.

Problem:
When the battery gets deeply discharged, the system shuts down correctly. But during sunrise, the solar panel initially provides only very low power (few hundred mW). As soon as some voltage appears, the system tries to boot again:

  • buck converter starts

  • MCU starts

  • modem attempts initialization

This causes:

  • voltage collapse

  • repeated reboot/reset loops

  • battery not getting enough time to recover charge

I want to implement a proper firmware-based low-power recovery strategy on the OpenMV RT1062.

My idea:

  • Detect low battery condition

  • Put RT1062 into ultra-deep sleep

  • Completely power OFF the LTE modem

  • Wake only after battery voltage has recovered sufficiently

Questions:

  1. What is the lowest-power sleep mode practically achievable on OpenMV RT1062?

  2. Can the board wake periodically from deep sleep to check battery voltage?

  3. What is the recommended way to fully power-gate an LTE modem from firmware?

  4. Has anyone implemented a solar/battery recovery strategy like this on OpenMV?

  5. Is there a recommended hardware + firmware approach for hysteresis-based recovery?

I would appreciate guidance from anyone who has designed low-power solar IoT systems with OpenMV or RT1062.

Thanks.

2

Hi!

  1. The RT1062 can run down to 30uA when powered via the battery connector. You can also power it via a diode attached to RAW (on the R6 version). It will draw 30uA in this case via RAW via a diode too when sleeping.
  2. Yes, you can set a deep sleep wakeup timer that will wake it up after some number of seconds.
  3. You can control the LTE modem power via GPIO pins on the power rails for it.
  4. Not that I know of, however, this is an implementation specific thing.
  5. Let me answer below.

So, what you need to do is to implement a power control system in hardware. You basically want to avoid turning on the power rail output until voltage is stable. This is outside of the OpenMV Cam really, the system that controls the power rails should just not turn them on until they are ready.

As for powering the RT1062, if from VIN, I recommend a 100uF cap to handle the RT1062 turn on surge current on the PSU output. If you are powering via a diode to RAW then a 330uF cap. Without these, the RT1062 may brownout while booting causing it to crash.

For your idea:

  1. You can use the ADC pin on the RT1062 to detect the low battery condition.
  2. You can put it into deep sleep from the software.
  3. The RT10652 can control the LTE power of the modem. So, it turns that off/on.
  4. You can have the RT1062 sample the voltage periodically.

However, I’d recommend that you skip the RT1062 sampling the power rail and just not turn on the power until the solar panel voltage has recovered. You should be able to do this via the circuit of the system you are using, if possible.