BQ76952: Problem in establishing i2C communication

Hi Mounish,

I do not know if your issue is caused by hardware or software. Looking at your schematic, I see that the I2C pull-up resistors are connected to REG2. REG2 is disabled by default, so it needs to be enabled and set to 5V (using I2C). Do you have a voltage applied to this node until REG2 is enabled?

If you are looking for Arduino example code, I have noticed that one user has published a BQ76952 Arduino project on Github (https://github.com/pranjal-joshi/BQ76952Lib). It might be a helpful reference. 

Best regards,

Matt

Hi, when i try to read data from registers, It is always returning me 0xFF.

Let us compare this with an example in the software development guide. ( Read "Enable protections A") , 

here let us say addr= 0x9261

readDataMemory(unsigned int addr) {              // function for reading data from registers

Wire.beginTransmission(BQ_I2C_ADDR_WRITE);       //  This creates [0x10] in fig 3.2 software developement guide
Wire.write(CMD_DIR_SUBCMD_LOW);                       //    This creates [0x3E] in fig 3.2 software developement guide 
Wire.write(LOW_BYTE(addr));                                      //     [0x61]
Wire.write(HIGH_BYTE(addr));                                    //      [0x92]
Wire.endTransmission();                                              //      End transmission

Wire.beginTransmission(BQ_I2C_ADDR_WRITE);     //     This creates [0x10] in fig 3.2 software developement guide
Wire.write(CMD_DIR_RESP_START);                        //      [0x40]
Wire.endTransmission();                                              // Ends transmission

Wire.requestFrom(BQ_I2C_ADDR_READ, 1);            // Creates [0x11]
while(!Wire.available());                                                // wait till data is available
unsigned int b=Wire.read();                                          // store data in variable "b'      
Serial.println(b);                                                           // Print value in b

}

I always get 0xFF as output no matter what is written in the address..So I really doubt. Is this waveform correct? I read somewhere in the datasheet that the lower byte of the register address should be written to 0x3E and the upper byte of register address should be written to 0x3F .. Please help

Hi Mounish,

I did not see an answer to my question, "Looking at your schematic, I see that the I2C pull-up resistors are connected to REG2. REG2 is disabled by default, so it needs to be enabled and set to 5V (using I2C). Do you have a voltage applied to this node until REG2 is enabled?"

Best regards,

Matt

Hi Matt Sunna,

Yes, I have connected pull up resistors externally. Communication has been established, I was able to read all cell voltages using direct commands 0x14 to 0x32, . I even turned on FETs using FET_ENABLE-0x0022. but now I need to turn on REG1 and REG2, but before that, I would like to read default values in the registers..

Hi Mounish,

Are you waiting long enough between sending the command to 0x3E and reading back from 0x40? Try inserting a 2ms wait time just before reading from 0x40. When you see 0xFF returned, this might mean the data is not available yet. Table 9-2 of the TRM shows the typical time it takes for the different subcommands to execute.

Best regards,

Matt