Hello,
I’m facing a strange issue with the CM4 module when booting from an MMC card. With an older batch, the boot process works fine, but with the new batch, for some reason, the SD signal voltage is being reduced from 3.3V to 1.8V. The SD_VDD_OVRIDE pin (73) is floating. I’ve tried pulling it to GND, but it doesn’t make any difference. When I remove the card, the levels on the CMD and CLK signals return to the normal 3.3V, so I don’t think the issue is related to SD_VDD_OVRIDE. I urgently need help with this.
Regarding the setup: The setup is identical to the one used with the CM4 IO board, except that instead of a 12k resistor, I used a 10k resistor on the switch/signal SD_PWR_ON. The signal is always high, and I can’t detect any reset. Another modification I made is using 33-ohm resistors on the signal lines, but this was also part of the previous batch.
I’m facing a strange issue with the CM4 module when booting from an MMC card. With an older batch, the boot process works fine, but with the new batch, for some reason, the SD signal voltage is being reduced from 3.3V to 1.8V. The SD_VDD_OVRIDE pin (73) is floating. I’ve tried pulling it to GND, but it doesn’t make any difference. When I remove the card, the levels on the CMD and CLK signals return to the normal 3.3V, so I don’t think the issue is related to SD_VDD_OVRIDE. I urgently need help with this.
Regarding the setup: The setup is identical to the one used with the CM4 IO board, except that instead of a 12k resistor, I used a 10k resistor on the switch/signal SD_PWR_ON. The signal is always high, and I can’t detect any reset. Another modification I made is using 33-ohm resistors on the signal lines, but this was also part of the previous batch.
Statistics: Posted by gs105 — Mon Dec 16, 2024 2:21 pm