BQ27427: Reading the remaining capacity

Hello Aslam, 

Can you please provide me with the log file and gg file obtained by bqStudio for this behavior? Additionally, have you completed a learning cycle? 

Regards, 

Jonny. 

Hi Jhonny,

I am not using bqStudio to configure the values. I am directly giving I2C commands from the controller. Please find the code snippets below:

void change_chemistry_profile(uint16_t chem_id )
{
//unseal the fuel gauge
gauge_cmd_write(CTRL, UNSEAL_KEY);
gauge_cmd_write(CTRL, UNSEAL_KEY);

gauge_cfg_update();
gauge_cmd_write(CTRL,chem_id);
gauge_exit();

gauge_cmd_write(CTRL, SEAL_KEY);

}

int change_battery_parameters(void)
{
uint8_t pData[DC_STATE_LENGTH]; //DC_STATE_LENGTH = 32
int ret=1;
//unseal the fuel gauge
gauge_cmd_write(CTRL, UNSEAL_KEY);
gauge_cmd_write(CTRL, UNSEAL_KEY);

ret = gauge_read_data_class(DC_STATE, pData, DC_STATE_LENGTH);

pData[6] = (DESIGN_CAPACITY & 0xFF00) >>8;
pData[7] = DESIGN_CAPACITY & 0xFF;
pData[8] = (DESIGN_ENERGY & 0xFF00) >>8;
pData[9] = DESIGN_ENERGY & 0xFF;

gauge_cfg_update(); // required for ROM gauge
ret = gauge_write_data_class(DC_STATE, pData, DC_STATE_LENGTH);
gauge_exit(); // required for ROM gauge

// gauge_read_data_class(DC_STATE, pData, DC_STATE_LENGTH);

//seal the fuel gauge
gauge_cmd_write(CTRL, SEAL_KEY);

return ret;
}

int gauge_read_data_class(uint8_t nDataClass, uint8_t *pData, uint8_t nLength)
{
    uint8_t nRemainder = nLength;
    uint16_t nOffset = 0;
    uint8_t nDataBlock = 0x00;
    uint16_t nData;

    if (nLength < 1)
        return -1;

    do
    {
        nLength = nRemainder;
        if (nLength > 32)
        {
            nRemainder = nLength - 32;
            nLength = 32;
        }
        else nRemainder = 0;

        nData = (nDataBlock << 8) | nDataClass;
        gauge_cmd_write(CMD_DATA_CLASS, nData);

        //if (hal_i2c_gauge_read(CMD_BLOCK_DATA, pData, nLength) != nLength) return -1;
        hal_i2c_gauge_read(CMD_BLOCK_DATA, pData, nLength);
        pData += nLength;
        nDataBlock++;
    } while (nRemainder > 0);

    return 0;
}

//check_sum: calculate check sum for block transfer
//pData: pointer to data block
//nLength: length of data block
uint8_t check_sum(uint8_t *pData, uint8_t nLength)
{
    uint8_t nSum = 0x00;
    uint8_t n;
    for (n = 0; n < nLength; n++)
        nSum += pData[n];
    nSum = 0xFF - nSum;
    return nSum;
}

//gauge_write_data_class: write a data class
//pHandle: handle to communications adapter
//nDataClass: data class number
//pData: buffer holding the whole data class (all blocks)
//nLength: length of data class (all blocks)
//return value: 0 = success
int gauge_write_data_class(uint8_t nDataClass, uint8_t *pData,uint8_t nLength)
{
    uint8_t nRemainder = nLength;
    uint16_t nOffset = 0;
    uint8_t pCheckSum[2] = {0x00, 0x00};
    uint16_t nData;
    uint8_t nDataBlock = 0x00;
    uint8_t temp_buff[8] = {0};

    if (nLength < 1)
        return 0;

    do
    {
        nLength = nRemainder;
        if (nLength < 32)
        {
            nRemainder = nLength - 32;
            nLength = 32;
        }
        else nRemainder = 0;

       // gauge_cmd_write(0x61, 0x00);  //enable block data memory
        temp_buff[0] = 0x00;
        hal_i2c_gauge_write(0x61,temp_buff,1);

       // nData = (nDataBlock << 8) | nDataClass;
        //gauge_cmd_write(CMD_DATA_CLASS, nData); //DataBlockClass() command
        temp_buff[0] = 0x52;
        hal_i2c_gauge_write(CMD_DATA_CLASS,temp_buff,1);

        //gauge_cmd_write(0x3F, 0x00);  //block offset location
        temp_buff[0] = 0x00;
        hal_i2c_gauge_write(0x3F,temp_buff,1);

       // if (gauge_write(pHandle, CMD_BLOCK_DATA, pData, nLength) != nLength)
         //   return -1;

        hal_i2c_gauge_write(CMD_BLOCK_DATA, pData, nLength);

        pCheckSum[0] = check_sum(pData, nLength);
        hal_i2c_gauge_write(CMD_CHECK_SUM, pCheckSum, 1);
        usleep(10000);

       // gauge_cmd_write(CMD_DATA_CLASS, nData);
        temp_buff[0] = 0x52;
        hal_i2c_gauge_write(CMD_DATA_CLASS,temp_buff,1);

        hal_i2c_gauge_read(CMD_CHECK_SUM, pCheckSum + 1, 1);

        if (pCheckSum[0] != pCheckSum[1])
            return -2;
        pData += nLength;
        nDataBlock++;
    } while (nRemainder > 0);

    return 0;
}

#define MAX_ATTEMPTS 5
bool gauge_cfg_update(void)
{
    uint16_t nFlags;
    int nAttempts = 0;
    gauge_control(SET_CFGUPDATE);

    do
    {
        nFlags = gauge_cmd_read(CMD_FLAGS);
        if (!(nFlags & CFGUPD)) usleep(500000);
    } while (!(nFlags & CFGUPD) && (nAttempts++ < MAX_ATTEMPTS));

    return (nAttempts < MAX_ATTEMPTS);
}

//gauge_exit: exit configuration update mode for rom gauges
//pHandle: handle to communications adapter
//nSubCmd: sub command to exit configuration update mode
//return value: true = success, false = failure
bool gauge_exit(void)
{
    uint16_t nFlags;
    int nAttempts = 0;

    gauge_control(SOFT_RESET);
    do
    {
        nFlags = gauge_cmd_read(CMD_FLAGS);
        if (nFlags & CFGUPD) usleep(500000);
    } while ((nFlags & CFGUPD) && (nAttempts++ <MAX_ATTEMPTS));

    return (nAttempts < MAX_ATTEMPTS);
}

If I re-initialize the fuel gauge before every read, the value is coming as expected.

Hello Aslam, 

I suspect the issue is with the configuration. When the gauge is POR, the gauge defaults to its default parameters, not the parameters you have programmed into the gauge. In order to be able to further debug this, I will need your configuration. 

Regards, 

Jonny. 

Hi Jhonny,

During the POR, the gauge defaults to its default parameters. Thats happening correctly. And my configuration values also updating properly. Below are my configuration values:

1. chemical ID : 0x1202 (4.2V)

2. Design capacity (700mAh)

3. Design Energy (2.59 Wh)

The issue is that I have to give SOFT_RESET command to the gauge before any read (like SOC, remaining capacity etc), then only I am getting proper values. 

If I am not giving SOFT_RESET command to the gauge before any read, I am not getting proper values.

Is this expected behavior of this fuel gauge.

Hello, 

After configuring the gauge, the SOFT_RESET subcommand is used to exit the CONFIG UPDATE mode to resume normal gauging. In order to be able to fully debug this, I will need the full gauge configuration, similar to that from the gg file. Additionally, how was the chemID matched? Typically we recommend using the GPCCHEM tool to ensure that the cell you are using is a good match with one of the three chemIDs to choose from in the bq27427. 

Regards, 

Jonny. 

Hi Jonny,

I have only changed three configuration values of the fuel gauge, other values are same as default configuration parameter. And we have chosen this chemical ID based on battery datasheet.

 Below are the changed configuration values:

1. chemical ID : 0x1202 (4.2V)

2. Design capacity (700mAh)

3. Design Energy (2.59 Wh)

Is any other critical battery parameter there?

I just need to read the SOC of the battery. No other functionalities are not needed for us now.

And we have very less time for this task. 

Currently, I need to give SOFT_RESET command to the gauge before any read (like SOC, remaining capacity etc), then only I am getting proper values. 

Regards,

Aslam