Quectel LTE Module Series User manual

SC20 Charging User Guide
LTE Module Series
Rev. SC20_Charging_User_Guide_V1.0
Date: 2016-09-26
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Copyright © Quectel Wireless Solutions Co., Ltd. 2016. All rights reserved.
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About the Document
History
Revision
Date
Author
Description
1.0
2016-09-26
Luffy ZHANG
Initial
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Contents
About the Document................................................................................................................................ 2
Contents.................................................................................................................................................... 3
Table Index ............................................................................................................................................... 4
1Introduction....................................................................................................................................... 5
2Debug................................................................................................................................................. 6
2.1. Related Code Files and Location.......................................................................................... 6
2.2. Debug................................................................................................................................... 6
3Compile and Download................................................................................................................... 11
4Charge.............................................................................................................................................. 12
4.1. Charging Process ...............................................................................................................12
4.2. Set Power-on/off Voltage ....................................................................................................12
4.3. The Maximum Charging Time.............................................................................................14
4.4. Abnormality.........................................................................................................................14
4.5. Query Device Information................................................................................................... 14
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Table Index
TABLE 1: RELATED CODE FILES AND LOCATIONS........................................................................................ 6
TABLE 2: BATTERY-TEMPERATURE MONITORING CALCULATIONS ......................................................... 10
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1Introduction
This document mainly describes debug codes for charging on Quectel SC20 module, which will help
customer to better understand the charging process.
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2Debug
2.1. Related Code Files and Location
Table 1: Related Code Files and Locations
Linux power_supply standard architecture enables power management on Android OS and data can be
sent to user space through Uevent mechanism.
2.2. Debug
Device Registration
The code for device registration is as follows:
static int qpnp_lbc_main_probe(struct spmi_device *spmi)
{
xxx
rc = power_supply_register(chip->dev, &chip->batt_psy); //Device registration
xxx
}
Code Files and Locations
Description
android/kernel/drivers/power/qpnp-linear-charger.c
Driver file for charging
android/kernel/arch/arm/boot/dts/qcom/batterydata-
palladium.dtsi
Battery parameters
android/kernel/arch/arm/boot/dts/qcom/msm-pm890
9.dtsi
Charging parameters
android/kernel/arch/arm/boot/dts/qcom/msm8909-p
m8909-mtp.dtsi
Charging switch
android/kernel/drivers/hwmon/qpnp-adc-common.c
Thermistor voltage and temperature table
qpnp-linear-charger.c
Driver file for charging, it is about device
registration, DTS parse, charging controlling, etc.
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static int qpnp_lbc_probe(struct spmi_device *spmi)
{
if (is_parallel_charger(spmi))
return qpnp_lbc_parallel_probe(spmi);
else
return qpnp_lbc_main_probe(spmi);
}
static int __init qpnp_lbc_init(void)
{
return spmi_driver_register(&qpnp_lbc_driver);
}
module_init(qpnp_lbc_init);
static void __exit qpnp_lbc_exit(void)
{
spmi_driver_unregister(&qpnp_lbc_driver);
}
module_exit(qpnp_lbc_exit);
MODULE_DESCRIPTION("QPNP Linear charger driver");
MODULE_LICENSE("GPL v2");
DTS Parse
DTS (Device Tree Source) is parsed by probe function.
static int qpnp_charger_read_dt_props(struct qpnp_lbc_chip *chip)
{ xxx
xxx
}
Charging Controlling
e.g.: when the battery temperature changes, charging current will become smaller to protect battery.
Please refer to the following code:
static void qpnp_lbc_set_appropriate_current(struct qpnp_lbc_chip *chip)
{
unsigned int chg_current = chip->usb_psy_ma;
if (chip->bat_is_cool && chip->cfg_cool_bat_chg_ma)
chg_current = min(chg_current, chip->cfg_cool_bat_chg_ma);
if (chip->bat_is_warm && chip->cfg_warm_bat_chg_ma)
chg_current = min(chg_current, chip->cfg_warm_bat_chg_ma);
if (chip->therm_lvl_sel != 0 && chip->thermal_mitigation)
chg_current = min(chg_current,
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chip->thermal_mitigation[chip->therm_lvl_sel]);
pr_debug("setting charger current %d mA\n", chg_current);
qpnp_lbc_ibatmax_set(chip, chg_current);
}
Battery Parameters
Battery parameters can be configured to calculate battery capacity, such as OCV (Open Circuit Voltage)
under different temperature and battery percentage.
qcom,pc-temp-ocv-lut{ xxx
}
Charging Parameters
Charging parameters includes high temperature percentage, low temperature percentage, battery cooling
threshold, battery warming threshold, charging current, etc., as shown below:
pm8909_chg: qcom,charger{
xxx
qcom,batt-hot-percentage = <35>; //High temperature percentage
qcom,batt-cold-percentage = <70>; //Low temperature percentage
qcom,cool-bat-decidegc = <100>; //Cooling threshold
qcom,warm-bat-decidegc = <450>; //Warming threshold
qcom,ibatmax-warm-ma = <360>; //Cooling current
qcom,ibatmax-cool-ma = <360>; //Warming current
xxx
}
Charging Switch
SC20 applies PMU internal charging and IC is pm8909, so customer needs to turn on pm8909 charger IC,
as follows:
&pm8909_chg {
status = "ok";
/* qcom,charging-disabled; */ //Comment out this line.
};
Thermistor Voltage and Temperature Table:
Thermistor voltage and temperature table is used to judge the accuracy of battery temperature that is
read.
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static const struct qpnp_vadc_map_pt adcmap_btm_threshold[] = {
{XXX, YYY}, //The former is the temperature value, and the latter is the voltage
}
The table is customized, it needs hardware engineers to get values from battery vendors and fill in.
High Temperature Shutdown
High temperature protection has been enabled on SC20, when the battery temperature is above 68
degrees, it will automatically shut down.
High temperature shutdown related files and codes are presented as follows:
1. android/frameworks/base/services/core/java/com/android/server/BatteryService.java: for executing
shutdown action.
private void shutdownIfOverTempLocked() {
//Shut down gracefully if temperature is too high (>68°C by default)
//Wait until the system has booted before attempting to display the shutdown dialog.
if (mBatteryProps.batteryTemperature > mShutdownBatteryTemperature) {
mHandler.post(new Runnable() {
@Override
public void run() {
if (ActivityManagerNative.isSystemReady()) {
Slog.e(TAG, "silent_reboot shutdownIfOverTempLocked");
Intent intent = new Intent(Intent.ACTION_REQUEST_SHUTDOWN);
intent.putExtra(Intent.EXTRA_KEY_CONFIRM, false);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
mContext.startActivityAsUser(intent, UserHandle.CURRENT);
}
}
});
}
}
2. android/frameworks/base/core/res/res/values/config.xml: set the temperature that triggers shutdown.
<!-- Shutdown if the battery temperature exceeds (this value * 0.1) Celsius. -->
<integer name="config_shutdownBatteryTemperature">680</integer>
If module shuts down immediately after being turned on, customer should first make sure that the battery
has power, then check whether it is caused by high temperature or not.
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High and Low Temperature Thresholds
High and low temperature thresholds are determined by both software and hardware, and hardware plays
a major role. On hardware side, the thresholds are closely related to thermistor and voltage divider
resistor of battery. On software side, customer only needs to choose the percentage from BTM
comparator of PM8909, which are listed as below, and calculate the thresholds by the following formula.
Table 2: Battery-temperature Monitoring Calculations
PM8909 internal comparator (pointed out by red arrow) is shown as below:
Figure 1: PM8909 Internal Comparator
Battery Charging Window
BTM Comparator Thresholds
Minimum Resistor Values
0 to 40 or 45ºC
70% to 35%
R_S1 = 39×(R_cold –R_hot)/70
R_S2 = (3×R_cold –13×R_hot)/10
-10 to 60ºC
80% to 25%
R_S1 = 3×(R_cold –R_hot)/11
R_S2 = (R_cold –12×R_hot)/11
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3Compile and Download
After debugging, customer needs to compile kernel and download kernel images.
1. Compile Kernel
make –jn bootimage(“n” means the thread numbers of CPU)
2. Download Kernel Images by Fastboot
adb reboot bootloader
fastboot flash boot android\out\target\product\msm8909\boot.img
fastboot reboot
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4Charge
4.1. Charging Process
Charging processes consists of four stages: trickle charging, constant current charging, constant voltage
charging and charging termination.
1. Trickle Charging
When battery voltage is lower than 3.2V, it is called trickle charging stage. This stage can be divided into
two phases: when battery voltage is lower than 2.8V, it is in first phase, and the current is 90mA. When
the voltage is greater than 2.8V and less than 3.2V, it is in the second phase, and the current is 450mA. In
trickle charging , it is the hardware that controls the charging behavior.
2. Constant Current Charging
The software system has been booted up in this stage, and it controls the charging behavior. The USB
charging current is 450mA and AC charging current is 1440mA.
3. Constant Voltage Charging
This stage begins when the battery voltage reaches VDD.
4. Charging Termination
Since pm8909 does not have ADC to detect current, so it is based on the battery capacity to judge the
charging status. When the value is100%, it indicates the charging is ended.
4.2. Set Power-on/off Voltage
Customer can set power-on voltage in boot_images\core\systemdrivers\pmic\config\msm8909\pm8909\
pm_config_target.c.
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In chg_app_ds array, 3500 indicates the power-on voltage is 3.5V. Customer can edit the value to change
the voltage.
Set power-off voltage setting in android\kernel\arch\arm\boot\dts\qcom\batterydata-palladium.dtsi.
In the palladium-battery data node, 3300000 indicates the voltage is 3.3V. Customer can edit the value to
change the voltage.
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4.3. The Maximum Charging Time
A timer can be enabled in the driver files according to the configuration in DTS (qcom, tchg-mins). When
charging timer reaches the set time, the module will stop charging.
Set timer as follows:
static int qpnp_lbc_tchg_max_set(struct qpnp_lbc_chip *chip, int minutes)
{
xxx
/* Enable timer */
rc = qpnp_lbc_masked_write(chip, chip->chgr_base + CHG_TCHG_MAX_EN_REG,
CHG_TCHG_MAX_EN_BIT, CHG_TCHG_MAX_EN_BIT);
if (rc) {
pr_err("Failed to write tchg_max_en rc=%d\n", rc);
return rc;
}
return rc;
}
4.4. Abnormality
When the battery temperature crosses high temperature threshold or low temperature threshold, it will
stop charging.
4.5. Query Device Information
You can query battery temp/capacity /health information via adb tool, for example:
adb root
adb remount
adb shell
cat /sys/class/power_supply/battery/temp //Query battery temperature
cat /sys/class/power_supply/battery/capacity //Query battery capacity
cat /sys/class/power_supply/battery/health //Query battery status
cat /sys/class/power_supply/battery/ voltage_now //Query battery voltage
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