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Helios64: Added UPS usage in Linux

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Aditya Prayoga 2020-10-26 14:26:08 +07:00
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@ -36,7 +36,7 @@ The battery pack is rated 7.2V 3180mAh (22.9Wh) with max continuous discharge of
## Charge Management
Battery charge is fully managed by hardware, no software required. Charging function still operates when system is powered off. Helios64 board provides a visual charging indicator on LED9.
Battery charge is fully managed by hardware ([Texas Instrument BQ24133](https://www.ti.com/product/BQ24133)), no software required. Charging function still operates when system is powered off. Helios64 board provides a visual charging indicator on LED9.
|LED State | Description |
|-----------|-------------|
@ -45,3 +45,66 @@ Battery charge is fully managed by hardware, no software required. Charging func
| Blinking | Fault / Battery Absent |
**Note:** The estimated time to fully charge the empty battery is around 4 hours.
## UPS Status Under Linux
In Linux, the UPS declared as gpio-charger located at
`/sys/class/power_supply/gpio-charger`
### Main Power Status
Main Power status can be read using
```bash
cat /sys/class/power_supply/gpio-charger/online
```
**1** means power adapter supplying the power.
**0** means loss of power, power adapter no longer supplying power.
### Charging Status
!!! Note
This status is unavailable on Linux Kernel 4.4
Battery charging status can be read using
```bash
cat /sys/class/power_supply/gpio-charger/status
```
It will return **Charging** or **Not Charging**
!!! Info
The status is only **valid** when main power is available.
*Fault / Battery Absent* status is unavailable but it can be concluded if the status keep changing.
### Battery Level
Battery voltage can be measured on internal ADC channel 2. The internal ADC is located at
`/sys/bus/iio/devices/iio:device0`
![!Battery level](/helios64/img/ups/battery_level_schematic.png)
Following table show scalling between ADC reading and actual battery voltage
| Battery Voltage (V) | ADC reading (mV) | Remarks |
|---------------------|------------------|---------|
| 0 | 114 | No batteries |
| 7.0 | 916 | Recommended threshold to force shutdown system |
| 8.4 | 1099 | Fully Charge |
[IIO subsystem](https://www.kernel.org/doc/html/latest/driver-api/iio/index.html) provide hardware raw value. To convert the raw value to standard units, use following formula
`adc = in_voltage2_raw * in_voltage_scale`
To get the actual ADC reading in shell run following command
```bash
echo "`cat /sys/bus/iio/devices/iio:device0/in_voltage2_raw` * `cat /sys/bus/iio/devices/iio:device0/in_voltage_scale`" | bc
```