USB Power draw advertisement

[askreet]

I'm unable to plug my ErgoDox (using QMK) into an iPad Mini because it claims the power draw is too high. I can't imagine it's exceeding 500mA, so I'm wondering if someone could point me in the direction of fixing this in the firmware, or if I am way off base with how to approach this. I'm willing to learn and write the patch to implement this change with some help, if it's appropriate.

Thanks in advance!

[Wilba6582]

Try changing:

.MaxPowerConsumption = USB_CONFIG_POWER_MA(500)

in tmk_core/protocol/lufa/descriptor.c to use 100 instead of 500. If that doesn't work, try 50.

[askreet]

Thanks for the tip -- I'll give that a shot.

Assuming it works, is this something qmk_firmware would want to record on a per-keyboard basis and bake into the resulting firmware? Is there a meaningful patch I could write to contribute this back to the community? Is "tmk_core" a vendored project I should be contributing to instead?

[NoahAndrews]

TMK and QMK have pretty thoroughly split ways at this point. Code you contribute to tmk_core probably won't end up back here in a timely fashion. I wouldn't be surprised if the max power consumption is already configurable by keyboard, but I'm not sure.

[jackhumbert]

I'm not sure where we stand on making the standard 100 (it was a one point to accommodate for using boards with iOS devices). It would be nice to be able to configure it per keyboard via the config.h file.

[Wilba6582]

I see no reason it shouldn't be configurable via config.h like the other USB descriptor info (i.e. name, desc, VID, PID) with a default of 500 if it isn't already defined before descriptor.c. i.e.

// top of descriptor.c
#ifndef USB_MAX_POWER_CONSUMPTION
#define USB_MAX_POWER_CONSUMPTION USB_CONFIG_POWER_MA(500)
#endif

[askreet]

Thanks @Wilba6582, I've got a patch up in #955 -- I opted to put the call to the CONFIG_POWER_MA macro in the descriptor body so the default/override defines are in mA, let me know if you prefer your original suggestion to that and I can swap it out.

[Wilba6582]

@askreet Your way is better ;-)