Quectel SC20 Charging User Manual

SC20 Charging User Guide

LTE Module Series

Rev. SC20_Charging_User_Guide_V1.0

Date: 2016-09-26

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Our aim is to provide customers with timely and comprehensive service. For any

assistance, please contact our company headquarters:

Quectel Wireless Solutions Co., Ltd.

Office 501, Building 13, No.99, Tianzhou Road, Shanghai, China, 200233

Tel: +86 21 5108 6236

Email: [email protected]

Or our local office. For more information, please visit:

http://www.quectel.com/support/salesupport.aspx

For technical support, or to report documentation errors, please visit:

http://www.quectel.com/support/techsupport.aspx

Or email to: [email protected]

GENERAL NOTES

QUECTEL OFFERS THE INFORMATION AS A SERVICE TO ITS CUSTOMERS. THE INFORMATION

PROVIDED IS BASED UPON CUSTOMERS’ REQUIREMENTS. QUECTEL MAKES EVERY EFFORT

TO ENSURE THE QUALITY OF THE INFORMATION IT MAKES AVAILABLE. QUECTEL DOES NOT

MAKE ANY WARRANTY AS TO THE INFORMATION CONTAINED HEREIN, AND DOES NOT ACCEPT

ANY LIABILITY FOR ANY INJURY, LOSS OR DAMAGE OF ANY KIND INCURRED BY USE OF OR

RELIANCE UPON THE INFORMATION. ALL INFORMATION SUPPLIED HEREIN IS SUBJECT TO

CHANGE WITHOUT PRIOR NOTICE.

COPYRIGHT

THE INFORMATION CONTAINED HERE IS PROPRIETARY TECHNICAL INFORMATION OF

QUECTEL CO., LTD. TRANSMITTING, REPRODUCTION, DISSEMINATION AND EDITING OF THIS

DOCUMENT AS WELL AS UTILIZATION OF THE CONTENT ARE FORBIDDEN WITHOUT

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OR DESIGN.

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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

1 Introduction ....................................................................................................................................... 5

2 Debug ................................................................................................................................................. 6

2.1. Related Code Files and Location .......................................................................................... 6

2.2. Debug ................................................................................................................................... 6

3 Compile and Download................................................................................................................... 11

4 Charge .............................................................................................................................................. 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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1 Introduction

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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2 Debug

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

}

 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.

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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3 Compile 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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4 Charge

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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