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USB question - Raspberry Pi

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As I read the USB2504 datasheet, pulling AM4 to GND will disable operation of the LEDs. Is it then permissible to pull AM1-AM3 and GR1-GR4 directly to VDD33 and GND, or must I still use the 47k resistors? Does AM4 still require a 47k resistor?

The upstream device for this hub is a Raspberry Pi CM4 board. When one USB device is initially connected to the hub, the CM4 will boot properly and additional devices can then be connected. If more than one USB device is initially connected to the hub, the CM4 attempts to boot repeatedly without success. Any suggestions?
 

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Hi,

As with your other thread ... it depends on many things. Like
* schematic
* PCB layout
* wiring
* power supply
* configuration in EEPROM
* type of USB devices
* and so on

We can only guess.
It sounds like a power supply problem. Here the LED current is expected to play only a minor role.
If I'm not mistaken: According USB specification the USB devices are not allowed to draw mor than 100uA (or some other low current) of current from USB port during power up in this "idle" state.
So my guess is that the USB devices do not keep in USB standard. (And draw too much current during power up)

Debug:
* use a scope to measure rPI supply voltage ( check on any short drop below 4.5V)
* check on ISB devices current, whether they keep on standards
( USB standard is freely available ... afaik)

Klaus
 

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Unless instructed so in the datasheet or reference manual, you must not short multi purpose pins to GND or VDD.

As for the reboot problem, is the USB hub supplied through USB or the same power supply as Rasperry Pi? In this case supply overcurrent may be the reason.
 

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FvM said:
Unless instructed so in the datasheet or reference manual, you must not short multi purpose pins to GND or VDD.

As for the reboot problem, is the USB hub supplied through USB or the same power supply as Rasperry Pi? In this case supply overcurrent may be the reason.
Click to expand...
So, I cannot pull-up or pull-down other pins AM1-4 or GR1-4?
 

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