Chinese source V1.1.0; kernel scope 4.4 / 4.19. Technical-preface scope includes module concepts, functions, configuration and troubleshooting. No English PDF exists in this input: all four languages are derived fully from the Chinese source and use its original technical figures where present. ArmSoM platform reference only: verify the actual board PMIC, SoC, SDK/BSP, kernel, power tree and battery specifications. No hardware tests or blanket board-support claims.
Code, parameters and logs are manufacturer examples, not ArmSoM measurements. Power, charging-current, voltage or thermal changes can cause power loss, damage or battery hazards; do not apply examples blindly and never disable thermal protection in normal use. Source discrepancies are retained without guessing constants; see this article’s editorial notes. Logs are source samples; values across phases do not establish one continuous test or actual battery state.
Technical preface: RK818/RK816 provide fuel gauging and charging management with similar implementations. RK818 illustrates important logs at each stage; RK816 refers to the same explanations.
1. Charger/OTG detection
1.1 Driver files
drivers/power/rk818_charger.c
This driver detects charger/OTG connection and removal and configures charging current. Messages use the prefix “rk818-charger: “. “ac”, “usb”, “dc” and “otg” identify different devices: 1 means connected and 0 disconnected. The PMIC itself cannot detect charger/OTG connection events, so charger-type detection actually relies on USB notifier-chain messages.
1.2 probe phase
DC-charger registration:
rk818-charger: support dc
rk818-charger: not support dc
Registering the Type-C charger notifier chain:
rk818-charger: register typec extcon evt notifier
Registering the conventional USB charger notifier chain:
rk818-charger: register bc evt notifier
Device connections when probe ends:
rk818-charger: ac=1, usb=0, dc=0, otg=0
Driver version:
rk818-charger: driver version: 2.0
1.3 running phase
Charger/OTG connection and removal events from the USB notifier chain:
rk818-charger: receive bc notifier event: DISCNT // 充电器拔出
rk818-charger: receive bc notifier event: USB // 电脑充电插⼊
rk818-charger: receive bc notifier event: AC // 标准充电器插⼊
rk818-charger: receive bc notifier event: CDP1.5A // CDP类型充电器插⼊
rk818-charger: receive bc notifier event: UNKNOWN // 不识别的充电器插⼊
rk818-charger: receive bc notifier event: OTG ON // OTG插⼊
rk818-charger: receive bc notifier event: OTG OFF // OTG拔出
rk818-charger: detect dc charger in // DC插⼊
rk818-charger: detect dc charger out // DC拔出
The PMIC cannot identify the charger type, but can determine whether charging equipment is connected:
rk818-charger: pmic: plug out
rk818-charger: pmic: plug in
Changes to the 5V supply when connecting/removing OTG devices:
rk818-charger: disable otg5v
rk818-charger: enable otg5v
Device and current information is updated after every charger/OTG connection or removal:
rk818-charger: ac=1 usb=0 dc=0 otg=0 v=4200 chrg=1000 input=1800 virt=0
1.4 suspend phase
OTG 5V supply changes during suspend:
rk818-charger: suspend: otg 5v on
rk818-charger: suspend: otg 5v off
1.5 shutdown phase
Current device connections during shutdown:
rk818-charger: shutdown: ac=1 usb=0 dc=0 otg=0
2. Battery-charge detection
2.1 Driver files
drivers/power/rk818_battery.c
drivers/power/rk818_battery.h
This driver implements the fuel gauge and provides battery-charge accounting. Messages use “rk818-bat: “ for identification.
2.2 probe phase
The first power-on after connecting a battery produces “first on”:
rk818-bat: first on: dsoc=24, rsoc=24 cap=960, fcc=4000, ov=3840
If an abnormal shutdown, such as continued consumption after a crash, leaves the coulomb counter abnormal, the next boot forces a correction:
rk818-bat: system halt last time... cap: pre=2400, now=120
If U-Boot has already initialized the fuel gauge, the kernel driver can skip parts of initialization to avoid repeating it:
rk818-bat: initialized yet..
Initial coulomb-counter state during probe:
rk818-bat: dsoc=32 cap=1000 v=3780 ov=3900 rv=3890 min=25 psoc=32 pcap=1000
Fuel-gauge version:
rk818-bat: driver version 7.1
2.3 running phase
Whenever the charge changes and the driver reports it to the framework, it prints the following. The first message gives live parameter states; the second gives the parameter states captured during boot initialization, mainly for debugging.
rk818-bat: changed: dsoc=22, rsoc=24, v=3820, ov=3770 c=1018, cap=960, f=4000,
st=cc cv, hotdie=0
rk818-bat: dl=10, rl=12, v=3670, halt=0, halt_n=0, max=0, init=0, sw=0, calib=0,
below0=0, force=0
2.4 suspend phase
After the system enters deep sleep, a long standby may let the battery fall below the shutdown voltage. The PMIC then generates a wake interrupt, followed by shutdown:
rk818-bat: lower power yet, power off system! v=3350, c=-125, dsoc=0
2.5 shutdown phase
Important information displayed at shutdown:
rk818-bat: shutdown: dl=0 rl=2 c=-1220 v=3460 cap=88 f=4000 ch=1 n=0 mode=1
rest=128
Meaning, in order: <displayed SOC> <real SOC> <current> <voltage> <remaining capacity> <full-charge capacity> <charger present?> <ignore remaining fields…>.
3. About the RK816 fuel gauge
RK816 fuel-gauge implementation is substantially similar to RK818. Charger detection and fuel-gauge changes are combined in:
drivers/power/rk816_battery.c
Message content is very similar to RK818, with the prefix “rk816-bat:” for identification. Refer to the RK818 explanations above for RK816.