USB - Descriptors demand only 100ma

[henrygab]

Configuration Descriptor shows 100ma demanded

Using USBTreeView.exe, it shows:

      ========================== Summary =========================
Vendor ID                : 0x1209 (Unknown Vendor)
Product ID               : 0x7332
USB Version              : 2.0 -> but Device is Full-Speed only
Port maximum Speed       : High-Speed (Companion Port 1-19-3 supports SuperSpeed)
Device maximum Speed     : Full-Speed
Device Connection Speed  : Full-Speed
Self powered             : no
Demanded Current         : 100 mA
Used Endpoints           : 9

and

    ------------------ Configuration Descriptor -------------------
bLength                  : 0x09 (9 bytes)
bDescriptorType          : 0x02 (Configuration Descriptor)
wTotalLength             : 0x00A4 (164 bytes)
bNumInterfaces           : 0x05 (5 Interfaces)
bConfigurationValue      : 0x01 (Configuration 1)
iConfiguration           : 0x00 (No String Descriptor)
bmAttributes             : 0x80
 D7: Reserved, set 1     : 0x01
 D6: Self Powered        : 0x00 (no)
 D5: Remote Wakeup       : 0x00 (no)
 D4..0: Reserved, set 0  : 0x00
MaxPower                 : 0x32 (100 mA)

This appears to match the code. See the final argument to the macro:

BusPirate5-firmware/usb_descriptors.c

Lines 164 to 165 in 5bbaed7

	// Config number, interface count, string index, total length, attribute, power in mA
	TUD_CONFIG_DESCRIPTOR(1, ITF_NUM_TOTAL, 0, CONFIG_TOTAL_LEN, 0x00, 100),

And while high-speed isn't supported, it's also configured at:

BusPirate5-firmware/usb_descriptors.c

Lines 187 to 188 in 5bbaed7

	// Config number, interface count, string index, total length, attribute, power in mA
	TUD_CONFIG_DESCRIPTOR(1, ITF_NUM_TOTAL, 0, CONFIG_TOTAL_LEN, 0x00, 100),

Should this be changed to 500mA?

The BP5 is a USB2 chip (full-speed only, not high-speed capable), even though it has a USB-C connector. Since it has a USB-C connector, does the BP5 have hardware to detect if the upstream port is USB3? (e.g., 45 Ohms termination on Rx+ and Rx-pins, and detecting upstream port sending Rx_detect pulses) If so, that would make it safer to draw up to 900mA (as allowed by USB-C), even without USB3-PD support.

See https://electronics.stackexchange.com/a/659195 (including first comment to the answer).