Reading Battery

1

Quick question. I am using the mangOH red with the WP8548 and i am trying to read the battery level using the Input Power Supply Monitoring API provided by modem Services. The battery level returned by le_ips_GetBatteryLevel always equals to zero, according to the documentation that means the battery is drained or it doesn’t have a battery connected. The battery definetly isn’t drained because i am able to power my platform only using the battery. Also le_ips_GetPowerSource always tells me it is powered by an external source and not the battery (even after disconnecting all usb connections).

Am I using the API wrong or is it because of the mangOH board?

2

I don’t see problem on mangoh red board with WP8548:

root@fx30:~# cm ips read
[ 53.760750] Alignment trap: netmgrd (823) PC=0x4d374280 Instr=0xe1c980d0 Address=0xb6704ed6 FSR 0x001
[ 53.771127] Alignment trap: netmgrd (823) PC=0x4d374284 Instr=0xe1c320d0 Address=0xb6704ede FSR 0x001
Voltage: 3630 mV
Powered by an external source
root@fx30:~# cm info
Device: WP8548
IMEI: 359377060004735
IMEISV: 2F
FSN: LL537500110203
Firmware Version: SWI9X15Y_07.13.07.00 92cfd2c jenkins 2018/08/22 19:18:52
Bootloader Version: SWI9X15Y_07.13.07.00 92cfd2c jenkins 2018/08/22 19:18:39
[ 56.373660] qup_i2c qup_i2c.0: QUP: I2C status flags :0x1300c8, irq:187
[ 56.379307] qup_i2c qup_i2c.0: I2C slave addr:0x3a not connected
MCU Version: 002.004
PRI Part Number (PN): 9904889
PRI Revision: 01.11
Carrier PRI Name: ATT
Carrier PRI Revision: 001.036_000
SKU: 1102621
Last Reset Cause: Unknown
Resets Count: Expected: 0 Unexpected: 0

3

I get Pretty much the same:

root@swi-mdm9x15:~# cm ips read
Voltage: 3692 mV
Powered by an external source
root@swi-mdm9x15:~# cm info
Device: WP8548
IMEI: 359377060821351
IMEISV: 30
FSN: LL919601200810
Firmware Version: SWI9X15Y_07.14.01.00 595652d jenkins 2018/10/26 08:34:29
Bootloader Version: SWI9X15Y_07.14.01.00 595652d jenkins 2018/10/26 08:48:35
MCU Version: 002.004
PRI Part Number (PN): 9906351
PRI Revision: 01.01
Carrier PRI Name: GENERIC
Carrier PRI Revision: 001.042_000
SKU: 1103113
Last Reset Cause: Unknown
Resets Count: Expected: -1 Unexpected: -1

But according to: cm - Legato Docs cm ips read should also display the battery level and specify that it is powered by the battery if one is connected and powering the board

4

didn’t you say it is returning zero?

5

I mean after calling:

uint8_t battery;
le_ips_GetBatteryLevel(&battery);

inside an App the variably Battery always contains 0.

API Documentaion: le_ips_interface.h File Reference - Legato Docs

6

ips command is also using this API, you need to investigate why “cm ips” can read value but your app cannot.

7

But “cm ips” obviously doesn’t display the battery value and displays it is powered by an external source even if it is powered by a battery. Also i can use the API in the app and get the power source and voltage levels.

Edit: With BatteryLevel i mean the battery percentage and not the voltage, sorry if that was unclear

8

how about using AT!MADC?0

9

There i get the following:

AT!MADC?0
!MADC: 3.65

OK

10

How exactly does le_ips_GetBatteryLevel(&battery); calculate the percentage? Maybe i can replicate it myself

11

seems it cannot really get the percentage…
I found that there maybe already an application for this:

12

I looked throug the source code and found following function:

static unsigned int ComputePercentage
(
unsigned int mAh
)
{
// Compute the battery charge percentage, rounding up from half a percent or higher.
uint32_t percentTimesTen = 1000UL * mAh / Capacity;
unsigned int percentage = (percentTimesTen / 10);
if ((percentTimesTen % 10) >= 5)
{
percentage += 1;
}

// Clamp at 100%
if (percentage > 100)
{
    LE_WARN("Battery monitor reports available charge (%u mAh) higher than maximum of %u mAh.",
            mAh,
            (unsigned int)Capacity);
    percentage = 100;
}

return percentage;

}

“Capacity” is just the battery Capacity, which i could set myself depending on the battery.

The mAh is the remaining charge calculated in another function using:

char path[256];

int pathLen = snprintf(path, sizeof(path), "%s/%s", MonitorDirPath, ChargeNowFileName);
LE_ASSERT(pathLen < sizeof(path));

int32_t uAh;
le_result_t r = util_ReadIntFromFile(path, &uAh);
if (r == LE_OK)
{
    *charge = uAh / 1000;
}

The weird thing is, “MonitorDirPath” is set via:
static const char MonitorDirPath = “/sys/class/power_supply/LTC2942”;

and it seems i don’t have the path on my mangOH specified in MonitorDirPath

13

did you install the driver?

14

I am not sure if it’s worth installing just yet. Because the final version of the Project i am working on will be independent from the mangOH red and the WP will have its own custom carrier board.

Still, thank you for your help!