Setting USB Power and a few other newbie questions

[stevecolt]

I'm looking at using a Pi-Pico in a small USB-powered and connected instrument that involves LED lights (6x 20ma) and a small stepper motor that can take 300ma. So I really need to make sure that the USB once enumerated will deliver the maximum USB2.0 rated 500ma. (assumes the computer side port can be configured as well, but most seem to, as I've been running this hardware running with a Nano for a while, and only changed the micro.
I'm using The 2.73 Library and so far most things have worked really well, and seems far more compatible than the official embed solution which I wasted a week on before swapping. I run this on VisualMicro under VisualStudio2019.
Whilst debugging my code I stumbled across a .json file that had an entry about 'set max USB power to 250ma', perhaps all I have to do is change this, but sadly I'm struggling to find it again. Was I dreaming? USBView also confirms max power is 250mA
I realise that 250mA is probably enough for most people and that it's probably set to limit power for the 3V3 to less than the 300ma for the regulator, but I'll be happy with <100ma for the 3v3 volts.
Thanks for any feedback.
Steve

[earlephilhower]

Yes, if you update the JSON being selected by Platform.IO, it will set a -D define that will update the USB descriptor sent to the host (there's no actual change to the app running, this is just a USB information change).

arduino-pico/cores/rp2040/RP2040USB.cpp

Lines 270 to 273 in fd1596b

	uint8_t tud_cfg_desc[TUD_CONFIG_DESC_LEN] = {
	// Config number, interface count, string index, total length, attribute, power in mA
	TUD_CONFIG_DESCRIPTOR(1, interface_count, USBD_STR_0, usbd_desc_len, TUSB_DESC_CONFIG_ATT_REMOTE_WAKEUP, USBD_MAX_POWER_MA)
	};

[maxgerhardt]

And for completeness' sake, the generating code for the USB max mA rating is in the makeboards.py

arduino-pico/tools/makeboards.py

Lines 322 to 327 in 354edb3

	# Raspberry Pi
	MakeBoard("rpipico", "Raspberry Pi", "Pico", "0x2e8a", "0x000a", 250, "RASPBERRY_PI_PICO", 2, "boot2_w25q080_2_padded_checksum")
	MakeBoard("rpipicow", "Raspberry Pi", "Pico W", "0x2e8a", "0xf00a", 250, "RASPBERRY_PI_PICO_W", 2, "boot2_w25q080_2_padded_checksum")
	# 0xCB
	MakeBoard("0xcb_helios", "0xCB", "Helios", "0x1209", "0xCB74", 500, "0XCB_HELIOS", 16, "boot2_w25q128jvxq_4_padded_checksum")

If you were using Platformio, you would have to add

build_unflags = -DUSBD_MAX_POWER_MA=250
build_flags = -DUSBD_MAX_POWER_MA=500

to the platformio.ini.
But since you say

I run this on VisualMicro under VisualStudio2019.

this extension will likely read the boards.txt of the Arduino core, so find the file locally and change

arduino-pico/boards.txt

Line 42 in 354edb3

rpipico.build.usbpwr=-DUSBD_MAX_POWER_MA=250

accordingly.

[stevecolt]

Well thank you both very much for your prompt replies.
Perhaps a little naughty but I just edited the boards.txt file as it was only changing 250 to 500 and that seemed to work according to USB TreeView so thanks a lot for your help.
Problem solved!!
Steve