Hi, would like to use the Beaglebone Black’s battery interface as a UPS power backup. This UPS system should enable Linux to power up and down the system. Has anyone done this?
The PMIC (tps65217) is capable of generation an interrupt when the PB_IN button is pressed as well as when power source changes (AC, USB, or BAT). I would the power source changes interrupt to call the same interrupt handler as the PB_IN button. This should power up and down the system when power is lost/restore.
Thank you for your help.
I’m not quite sure what your question is …
The PMIC incorporates a battery charger and can be configured via I2C. You shouldnt need to be concerned with PMIC interrupts, although this would depend on your specific needs. You can just monitor external power using a GPIO if that’s easier than getting it from the PMIC.
One thing to be aware of - the li-ion cell is at the 3V level, so when 5V power is lost, USB power is also lost.
1 Like
Thank you, Paul,
I understand that Battery is only 3.7 volts. I need a way to Power down Linux OS when power is lost.
The PMIC also take care of the power push button on the Beaglebone. As far as I can tell, when the PWR_PB is pressed the PMIC generates an interrupt. This interrupt handler will generate a System Power Down call and Linux will clean everything up power down.
I want to enable the AC interface functionality in the PMIC. When this interrupt occurs, I can call the PWR_PB interrupt handler (maybe need some mask bit changed) to power down the system. When the power is restored, the system will boot up and run.
Thank you
Have you concidered simply using the shutdown or halt command when you detect that input power has been lost? You can detect loss of power by polling the PMIC status, or by using a GPIO. I havnt looked into this at all, but I would imagine this would be simpler that trying to hook into the PMIC interrupts.
Yes, that is my plane B approach.
I wanted to see if I could use the PMIC first. I like this chip and planning on using it in other projects if it works out.
Could you point me to where I can find the interrupt handler?
Thank you
Thank you foxsquirrel,
I have the datasheet. I am looking for the Linux PMIC Interrupt handler’s code. I am not sure if it is part of u-boot or Linux Kernal.
I got my U-Boot and Linux Kernal code from here.
GitHub - u-boot/u-boot: "Das U-Boot" Source Tree and GitHub - RobertCNelson/linux-stable-rcn-ee
Thank you again.
What I seen is the the pins, are those pins on the lower right actually connected to the BBB. If they are not connected or cannot be mux’d???
Hi,
I do not know what pins you are referring to.
I was looking at the int pin, just glanced at that and have not read anything.
Hi,
I believe they are connected because small power push button on the Beaglebone Black works for powering up and down.
I have been reviewing the hardware design and I believe there is no way to read the Push Button through GPIO.
It is posable Linux is Polling the I2C bus to see if the button is pushed.
I wonder what is going on with its i2c bus and how active it is. It would be assumed its talking back and forth with the kernel, do they possibly have a node in proc.
This is my first “Linux” type project. I don’t know what you mean by “node in proc”
From a PMIC point of view there is no need. It is a pretty much a set it and forget type part.
If you were do aggress power management, you could be adjusting power supplies value but the AM3352 is not really that type of chip.
fred@bbbi1:~$ cd /
fred@bbbi1:/$ ls
bin data etc ID.txt lost+found mnt proc run srv tmp var
boot dev home lib media opt root sbin sys usr
fred@bbbi1:/$ cd proc
fred@bbbi1:/proc$ ls
1 121 2 559 785 buddyinfo irq schedstat
10 129 20 560 789 bus kallsyms self
103 13 21 590 792 cgroups keys slabinfo
1032 133 2125 596 794 cmdline key-users softirqs
1033 1338 2133 600 795 config.gz kmsg stat
104 134 2150 612 796 consoles kpagecgroup swaps
1089 1382 2179 624 8 cpu kpagecount sys
11 139 2199 634 88 cpuinfo kpageflags sysrq-trigger
110 14 22 665 881 crypto loadavg sysvipc
111 140 2204 68 882 devices locks thread-self
1115 144 2206 69 89 device-tree meminfo timer_list
1130 145 23 70 9 diskstats misc tty
1131 146 24 71 91 driver modules uptime
1149 147 3 72 92 dynamic_debug mounts version
1150 148 4 727 94 execdomains mtd vmallocinfo
1154 1522 486 73 95 fb net vmstat
1159 16 487 74 96 filesystems pagetypeinfo zoneinfo
1165 17 526 76 98 fs partitions
1193 18 542 77 99 interrupts pressure
12 19 549 78 apm iomem pvr
120 1912 554 783 asound ioports sched_debug
fred@bbbi1:/proc$
That is the virtual filesystem with kernel information.
fred@bbbi1:/proc$ cat interrupts
CPU0
16: 332954 INTC 68 Level clockevent
17: 0 INTC 3 Level arm-pmu
19: 0 INTC 96 Level 44e07000.gpio
20: 15 INTC 72 Level 44e09000.serial
21: 285 INTC 70 Level 44e0b000.i2c
22: 0 INTC 16 Level TI-am335x-adc.0.auto
23: 1 INTC 78 Level wkup_m3_txev
25: 0 INTC 75 Level rtc0
26: 0 INTC 76 Level rtc0
29: 0 INTC 71 Level 4802a000.i2c
30: 0 INTC 65 Level 48030000.spi
31: 0 INTC 80 Level 48038000.mcasp_tx
32: 0 INTC 81 Level 48038000.mcasp_rx
38: 0 INTC 98 Level 4804c000.gpio
39: 0 INTC 64 Level mmc0
40: 0 INTC 77 Level mbox-wkup-m3
41: 102 INTC 30 Level 4819c000.i2c
42: 0 INTC 125 Level 481a0000.spi
45: 0 INTC 32 Level 481ac000.gpio
46: 0 INTC 62 Level 481ae000.gpio
48: 32105 INTC 28 Level mmc1
52: 0 INTC 36 Level tilcdc
53: 0 INTC 111 Level 48310000.rng
55: 21775 INTC 41 Level 4a100000.ethernet
56: 31292 INTC 42 Level 4a100000.ethernet
57: 4146 INTC 43 Level 4a100000.ethernet
58: 9494 INTC 12 Level 49000000.dma_ccint
60: 139 INTC 14 Level 49000000.dma_ccerrint
64: 0 INTC 18 Level musb-hdrc.0
65: 1 INTC 19 Level musb-hdrc.1
66: 0 INTC 17 Level 47400000.dma-controller
67: 0 INTC 109 Level 53100000.sham
69: 2 INTC 7 Level tps65217-irq
71: 2 tps65217 0 Edge vbus
72: 0 tps65217 2 Edge tps65217_pwr_but
143: 0 4804c000.gpio 25 Level tda998x
144: 0 44e07000.gpio 6 Edge 48060000.mmc cd
Err: 0
Thank you
It looks like I am on the correct trail.
