UPS-Lite

I like the (rewritten) script a lot, but it doesn't give much information. I also have a rpi 3b+ with a PiCO UPS, for which a nice python-script is written with lots of useful information. This is my attempt to add some features to UPS-Lite.py... And any help is welcome :)

Please note that I'm not a seasoned developer / debugger and this is work in progress... ;)

Wishlist...

as said: I'm spoiled with the output of pico_status.py:

Stuff on my wishlist:

• Powering mode: battery or outlet powered
• Charge state: discharging, charging or charged
• Temperature: nice to know, not a real must.

jan 2020 update

As it turns out, the UPS-lite doesn't provide much information, except voltage, capacity and some kind of firmware version. Unlike the PiCO UPS I use for the rpi 3b+, power always flows via the battery, so there's no way of telling if the zero is connected to a power source other than the UPS-Lite. There's also no easy way to tell of the battery is charging or not. The PiCO has a dedicated data-address showing the charge-state, UPS-Lite doesn't.

My version of UPS-Lite.py

So, here's what I did to the script to suit my needs:

Temp file

My script is run ad-hoc, so it can't keep variables in memory. This is why I write the current capacity and state to a temp-file (/tmp/ups_lite_capacity.tmp) to be used to calculate the charge-state.

read_status Function

I've written a new function to calculate the charge-state, comparing the current capacity with the previous capacity read from the tempfile. The previous state is also written to file and used in case the previous and current capacity are the same. I tried to use the voltage for calculation as well, but it fluctuates too much.

Look and feel

I changed the output a little bit more to my liking :)

temperature

The temperature of the Raspberry Pi itself can be read with 'vcgencmd', that's it. But, nice to know, so added to the output.

older notes:

i2c & UPS-Lite

i2cdetect shows that only one chip-address is accessible:

i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- 36 -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

i2cdump shows several data-addresses, of which currently only 0x02 (Voltage) and 0x04 (Capacity) are used in the current script.

i2cdump -y 1 0x36
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00: ff ff b5 20 23 0f 00 00 00 02 ff ff 97 00 ff ff
10: ff ff ff ff fb fa ff ff ff ff ff ff ff ff ff ff
30: ff ff ff ff ff ff ff ff ff ff ff ff ff ff 00 00

So... main question is: what does the rest do?

Not much information is to be found, but Max17040.pdf offers an interesting table:

The downside is that it only covers 0x00 - 0x0d and 0xfe - 0xff, and the text states that all remaining addresses are reserved and undefined...

data address	Function	Remark	byte Value	word Value
0x00	-	-	ff	0xffff
0x01	-	-	ff	fluctuates
0x02	VCELL	Used for Voltage calculation	fluctuates	fluctuates
0x03	VCELL	-	fluctuates	fluctuates
0x04	SOC	Used for State of charge	fluctuates	fluctuates
0x05	SOC	-	fluctuates	fluctuates
0x06	MODE	-	00	0x0000
0x07	MODE	-	00	0x0000
0x08	VERSION	-	00	0x0200
0x09	VERSION	-	02	0xff02
0x0a	-	-	ff	0xffff
0x0b	-	-	ff	0x97ff
0x0c	RCOMP	-	97	0x0097
0x0d	RCOMP	-	00	0xff00
0x0e	-	-	ff	0xffff
0x0f	-	-	ff	0xffff
0x14	-	Another kind of charge state counter	fluctuates	fluctuates
0x15	-	-	fluctuates	fluctuates
0x3e	-	-	00	0x0000
0x3f	-	-	00	0xff00

Powering Mode

I'm looking for a simple way to check if the pi is running on battery or not. From the current 2 outputs from the script (voltage and capacity) I can't determine the source of power. Unlike with the PiCO UPS, power is always drawn via the ups_lite battery. The Pi Zero appears to have no clue if it's running on a wall outlet or the battery...

Charge state

I've decided to always show the Charge state. Currently being 'low', 'full'. Trying to figure out how to determine if it is charging or not.

Temperature

Not sure if this is possible on a zero, but I'll give it a try... Figured out how to add SOC temperature to the script with vcgencmd.