Go measure the 5V, 3.3V and 1.8V rails of the CM4. My guess is that you've got a short somewhere. You're hearing coil whine from the SMPS struggling to supply current which causes the switching frequency to drop. Its triggering the protection circuitry inside the PMIC which causes it to cut out and restart.There is no speaker connected, the "beeping" comes from the CM4 itself. Also it isn't exactly a beep its more like a high pitched sound.
A separate issue is that SD_PWR_ON is not connected in the schematic.
The SD_PWR_ON signal is used to enable an external power-switch to turn on power to the SD card; for eMMC it typically isn’t used. If booting from SD card is required, then a pullup resistor must also be fitted to default the power-switch to be on.
Statistics: Posted by trejan — Sun Apr 07, 2024 9:40 pm