Please refer to this issue for the initial context of this question:
viewtopic.php?p=2364937#p2364937
As mentioned in that post, the other issue I'm having with my CM5 custom carrier board is the fan connector is not working. I've tested this by running the "stress" for 60 seconds with the "--cpu" option, and checking that the temperature of the CPU approach 80 degrees C. The fan did not run.
I have attempted to implement the suggestion on page 16 of the CM5 Datasheet (bolding mine) for ensuring the fan does not run at 100% when the CM5 is shut down:
"During CM5 shutdown, power supply shutdown includes Fan_PWM. If the PWM fan is powered from +5V, the fan will start or continue to run. To prevent the fan from running after power supply shutdown, turn off the supply to the fan. For example, you could use the same supply as the external USB ports use which is controlled by VBUS_EN. Alternatively, use an open collector buffer (e.g. 74LVC1G07) powered from +5V. Connect the input to CM5_3.3V. Connect the output in parallel with the PWM line."
See the attached schematic where the 74LVCG07 VCC is connected to +5 VDC, GND to GND, the input to +3.3 VDC from the CM5, and the output to pin 1 of the fan connector:
Using a multimeter to check the J1 fan connections, I find that:
Pin 1 is about +1.7 VDC when the CM5 is powered up. And does, indeed, drop to 0 VDC when the CM5 shuts down via "sudo poweroff".
Pin 2 is varies between +1.7 VDC and 0 VDC based on the setting of "pinctrl FAN_PWM".
Pin 3 measures +3.3 VDC.
Pin 4 is 0 VDC.
All of these measured relative to my GND test point.
So it appears I've botched my implementation of the suggestion in the datasheet. Does anybody have suggestions what I've done wrong in this case?
As with my other post, many thanks in advance for any help you can provide!
viewtopic.php?p=2364937#p2364937
As mentioned in that post, the other issue I'm having with my CM5 custom carrier board is the fan connector is not working. I've tested this by running the "stress" for 60 seconds with the "--cpu" option, and checking that the temperature of the CPU approach 80 degrees C. The fan did not run.
I have attempted to implement the suggestion on page 16 of the CM5 Datasheet (bolding mine) for ensuring the fan does not run at 100% when the CM5 is shut down:
"During CM5 shutdown, power supply shutdown includes Fan_PWM. If the PWM fan is powered from +5V, the fan will start or continue to run. To prevent the fan from running after power supply shutdown, turn off the supply to the fan. For example, you could use the same supply as the external USB ports use which is controlled by VBUS_EN. Alternatively, use an open collector buffer (e.g. 74LVC1G07) powered from +5V. Connect the input to CM5_3.3V. Connect the output in parallel with the PWM line."
See the attached schematic where the 74LVCG07 VCC is connected to +5 VDC, GND to GND, the input to +3.3 VDC from the CM5, and the output to pin 1 of the fan connector:
Pin 1 is about +1.7 VDC when the CM5 is powered up. And does, indeed, drop to 0 VDC when the CM5 shuts down via "sudo poweroff".
Pin 2 is varies between +1.7 VDC and 0 VDC based on the setting of "pinctrl FAN_PWM".
Pin 3 measures +3.3 VDC.
Pin 4 is 0 VDC.
All of these measured relative to my GND test point.
So it appears I've botched my implementation of the suggestion in the datasheet. Does anybody have suggestions what I've done wrong in this case?
As with my other post, many thanks in advance for any help you can provide!
Statistics: Posted by William Hachfeld — Sat Feb 21, 2026 8:23 pm — Replies 9 — Views 92