BQ27x00

How to use the BQ27x00 battery gas gauge.

Before installing the driver, the plateforme file (ie apf27-dev.c) has to be correctly modified to support the BQ27200 i2C chip.

Driver installation

 $ make linux26-menuconfig

Device Drivers--->
    <M> Power supply class support ---> 
        <M> BQ27200 battery driver

 $ make 

Update the APF27 board with the new Linux kernel and rootfs.

Usage

• Load the module:

modprobe bq27x00_battery

• Read internal temperature:

cat /sys/class/power_supply/bq27200-0/temp

• Read battery voltage:

cat /sys/class/power_supply/bq27200-0/voltage_now

• Read battery current:

cat /sys/class/power_supply/bq27200-0/current_now

Remark: the result (mA) has to be scaled depending on the shunt resistor (typically 0.2 0hms). The formula is then: result*3.57/20.

• Read capacity:

cat /sys/class/power_supply/bq27200-0/capacity

Remark: the capacity can only be estimated after a complete discharge/charge cycle. See BQ27200 datasheet for more informations.

Links

• BQ27200 datasheet