I wanted to measure the power consumption of my #Librem5 and didn't have a way to measure on the power lines off usb-c.

Looking at the #schematic and at /sysfs I found that I could use values provided by MAX17055 to get the current values when running on battery only:

watch_battery_voltage_current.sh:

#!/bin/bash
while sleep 0.05; do 
	C=`cat /sys/devices/platform/soc@0/30800000.bus/30a50000.i2c/i2c-3/3-0036/power_supply/max170xx_battery/current_now`
	V=`cat /sys/devices/platform/soc@0/30800000.bus/30a50000.i2c/i2c-3/3-0036/power_supply/max170xx_battery/voltage_now`
	
	if [ "$C" != "$OLD_C" ] || [ "$V" != "$OLD_V" ]; then 
		echo `date +'%s.%N'` $V $C
	fi
	OLD_C=$C; OLD_V=$V
done

There's much room for improvement:

• get changes pushed instead of polling (seems to be only possible using C)
• getting values at BQ25895 or BD71837 to be closer to where the power is needed

Any ideas are welcome!

Using #libreoffice I made the #diagram below which shows:

1. yellow vertical lines signaling a push of the power button. First line is power off the screen
2. green vertical lines with a red 'shadow' showing where the xhci usb-hub vanished.
3. during the period with screen on between the second and third yellow line I unloaded the xhci modules, cut the power to the modem briefly, and reloaded the modules
4. the modem draws a lot more power during registration after the reset than during average operation as can be seen on the right side of the third yeelow line(green line = current, relativ)
5. when a lot current is drawn the voltage (blue line) at max17055 goes down a bit
6. battery slowly depleting: average voltage going down

I did this for two reasons:

• I wanted to know how much power the modem draws to be able to compare it to other modems candidates to replace the broadmobi bm818
• While doing this and chatting about it with @craftyguy@freeradical.zone he had the idea that problems with the bus or modem could be related to brownout