SLAA476B February   2011  – July 2019 BQ2040 , BQ2040 , BQ2060A , BQ2060A , BQ2063 , BQ2063 , BQ2083-V1P3 , BQ2083-V1P3 , BQ2084-V143 , BQ2084-V143 , BQ2084-V150 , BQ2084-V150 , BQ2085-V1P3 , BQ2085-V1P3 , BQ20Z40-R1 , BQ20Z40-R1 , BQ20Z70-V160 , BQ20Z70-V160 , BQ20Z80A-V110 , BQ20Z80A-V110 , BQ28400 , BQ28400 , BQ78PL114 , BQ78PL114 , BQ78PL116 , BQ78PL116 , LM5145 , LM5145 , MSP430F5500 , MSP430F5500 , MSP430F5501 , MSP430F5501 , MSP430F5502 , MSP430F5502 , MSP430F5503 , MSP430F5503 , MSP430F5504 , MSP430F5504 , MSP430F5505 , MSP430F5505 , MSP430F5506 , MSP430F5506 , MSP430F5507 , MSP430F5507 , MSP430F5508 , MSP430F5508 , MSP430F5509 , MSP430F5509 , MSP430F5510 , MSP430F5510 , TPS40057 , TPS40057 , TPS40170 , TPS40170

 

  1.   Wide-Vin Battery Charger Using SMBus Communication Interface Between MSP430™ MCUs and bq Fuel Gauges
    1.     Trademarks
    2. 1  Introduction
    3. 2  Hardware
      1. 2.1 Overall System Description
      2. 2.2 MSP430F5510 Daughterboard Subsystem
        1. 2.2.1 Subsystem Description
        2. 2.2.2 MSP430F5510 Port Pins Functionality Description
      3. 2.3 Power Stage Board Subsystem
        1. 2.3.1 Subsystem Description
        2. 2.3.2 Input Protection Features
        3. 2.3.3 Constant-Voltage and Constant-Current Feedback
    4. 3  Software
      1. 3.1 SMBus Protocol Description
      2. 3.2 Software File Structure
      3. 3.3 API Calls Description
        1. 3.3.1  UCS_Init ( )
        2. 3.3.2  Timer_Init ( )
        3. 3.3.3  PWM_Init ( )
        4. 3.3.4  ADC_Init ( )
        5. 3.3.5  Fan_Init ( )
        6. 3.3.6  LED_Init ( )
        7. 3.3.7  SMBus_Initialize ( )
        8. 3.3.8  LED_Control ( )
        9. 3.3.9  Fan_Control ( )
        10. 3.3.10 VI_ADC_Read ( )
        11. 3.3.11 SMBus_Select ( )
        12. 3.3.12 Calibrate_Battery ( )
        13. 3.3.13 Delay_Timer ( )
        14. 3.3.14 PWM_Control ( )
        15. 3.3.15 Smbus_Access ( )
        16. 3.3.16 Smbus_Access_PEC ( )
        17. 3.3.17 crc8MakeBitwise ( )
      4. 3.4 Sample Application Description
    5. 4  SBS Supported Commands Using SMBus Protocol
    6. 5  Detailed Sample Application Flow Chart
    7. 6  Battery Status Register Description
      1. 6.1 BatteryStatus (0x16)
    8. 7  MSP430F5510 Daughterboard Schematics
    9. 8  Setting Up the MSP430F5510 Daughterboard Hardware
      1. 8.1 JTAG FET Debugger Interface (Power Up, Program and Debug Options)
      2. 8.2 eZ430 Emulator Interface (Power Up, Program and Debug Options)
      3. 8.3 Power Stage Board (Power Up Option Only)
    10. 9  Battery Calibration Circuit Setup
    11. 10 Battery Voltage and PWM Conversions
    12. 11 Battery Current and PWM Conversions
    13. 12 Power Stage Board Schematics (Generation 1: 40-V Input)
    14. 13 Bode Plot Measurement for Feedback Loop Stability Analysis
    15. 14 Power Stage Board Schematics (Generation 2: 60-V Input)
    16. 15 Setting Up the Power Stage Board Hardware
    17. 16 References
  2.   Revision History

3.3.16 Smbus_Access_PEC ( )

This function is implemented as a generic SMBus access function with packet error checking (PEC) implementation on the MSP430F5510 initialized to master mode. While similar to the SMBus_Access function, this function can either generate the PEC byte (if the master is transmitter) or can compare the PEC byte received against the internally computed one (if the master is receiver).

This function calls another function crc8MakeBitwise(), which computes the PEC byte within the MSP430F5510. In the master transmitter case, the PEC byte is appended last to the transmit buffer. If the slave fuel gauge returns an ACK immediately following the PEC byte, then data integrity was preserved during the transaction. On the other hand, if the return is a NACK, then some bits are being altered unintentionally during the transaction. In the case of the master receiver, the last byte in the receive buffer is the PEC byte. The PEC byte is internally generated, compared with the received one and if the bytes are equal, then a valid transaction occurred.

Function Definition

unsigned char Smbus_Access_PEC (unsigned char smbus_command, unsigned char read_write, unsigned char size_in_bytes {...}

Inputs

Name Type Description Example Value
smbus_command unsigned char One byte of SMBus command (0x00 to 0x7F). See Section 4 for a list of supported SMBus commands. SBS_CMD_VOLTAGE, SBS_CMD_CHARGING_CURRENT
read_write unsigned char Set the mode to either read data from or write data to the slave device. SMBUS_MASTER_MODE_READ, SMBUS_MASTER_MODE_WRITE
size_in_bytes unsigned char Based on the command syntax, size of the data set to be sent or received. 0x01 to 0x20
SMBus_Data_To_Slave unsigned char[] Array of data to be sent to the slave. The calling function should parse the data into byte-size elements and stuff them into this array.

Return

Name Type Description Example Value
smbus_access_status unsigned char Returns the status flag if the PEC byte sent by the slave fuel gauge matches the ones computed in the MSP430F5510 or if the PEC byte written by the MSP430F5510 is acknowledged by the slave device. FLAG_SUCCESS=0, FLAG_FAIL=1, FLAG_NACK=2
SMBus_Data_From_Slave unsigned char[] Array of data to be received from the slave. The calling function should concatenate the byte-size elements to construct the data received.

Example Function Call

To access the battery voltage through SMBus with PEC:

smbus_access_status = SMBus_Access_PEC(SBS_CMD_VOLTAGE, SMBUS_MASTER_MODE_READ, 2); // Tables for data to/from Slave Device declared with size of 32 bytes #define SMBUS_DATA_TO_SLAVE 32 //Table length unsigned char SMBus_Data_To_Slave[SMBUS_DATA_TO_SLAVE]; #define SMBUS_DATA_FROM_SLAVE 32 //Table length unsigned char SMBus_Data_From_Slave[SMBUS_DATA_FROM_SLAVE];