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BQ27510EVM: I can't read the SOC register properly.

Part Number: BQ27510EVM
Other Parts Discussed in Thread: BQ27510, EV2400, BQSTUDIO

I'm having difficulty reading from the bq27510.  I know the part is working properly because it reads the correct state of charge when I plug in the EV2400.  I'm attempting to do a single byte read of the SOC register.  The datasheet says the commands for the SOC register are 0x2C/0x2D.  When I 0x2C it returns 0x75 and when I try 0x2D it returns 0x09.  Neither are the correct state of charge which should be 0x63 (99%).

Here's what I'm sending to it and what I get back:

send 0xAA

send 0x2C

send 0xAB

receive 0x75


send 0xAA

send 0x2D

send 0xAB

receive 0x09

Any help I could get would be appreciated. Thanks

  • Hello Greg,

    You can use the Advanced Comm tab in bqStudio to read individual bytes and use the resulting waveforms as a reference.

    It is very likely that the host code that is reading the data needs an update.

  • Hi Shirish, I tried that, I read 2 bytes starting at register 0x2C and it returned 0x75 0x09 which is what I am reading.  So that at least confirms my reads are correct.  It just seems I am reading the wrong register.  What is the proper register to read from to receive state of charge?

  • So from using that advanced Comm tool, I have found that there is only one byte in the registers that corresponds with the state of charge, and that is register 0x20.  I watched that register while the battery was discharging and it always matched the stated SOC in the dashboard panel.  But the datasheet says this register is MaxLoadTimeToEmpty() and not the SOC register.

  • Hello Greg,

    You found the issue. I just checked and confirmed that bqStudio reads 0x020 to display StateofCharge. 0x2c is for Operation Config. Looks like an error in the datasheet.