We have a CM4 module inside an Andino IO module on their CM4 board.
The RPi4 bootloader is configured to start from our Samsung SSD980 512GB NVMe which has BalenaOS installed.
For communication, we have a 4G/LTE modem connected on the CM4 board USB port.
With everything connected, we sometimes get the “Danger! The device is undervolted!” warning in the Balena dashboard.
The system seems stable even with 4G connected. Assume the voltage is still just enough.
But we have issues with reboots:
- Sometimes, the boot hangs (status leds are no longer blinking)
- Sometimes, the modem is not initialized correctly and all modem commands time out.
Rebooting without modem, works stable.
We assume that, during startup, the SSD and 4G take too much current and cause the voltage to drop too low.
We want to try to enable the modem with a delay. So, we can spread the consumption and hopefully get stable reboots.
The modem is connected on the USB port which is enabled by the dtoverlay=dwc2.
Is there a way to delay this overlay?
Or another approach to delay the USB power?
I taught on delaying the NetworkManager interface but the modem is powered even before that service is started.