BQ25892EVM-664: i2c register mapping

Ben Pitcairn

Part Number: BQ25892EVM-664
Other Parts Discussed in Thread: BQ25892, BQ25890, BQSTUDIO

Hello,

I have a bq25892 eval board and have setup a microcontroller to communicate with it. I can read and write to a particular register fine.

However, the values I get back don't seem to make sense to me according to the data sheet. Is there a register offset or something I'm missing?

For example reading register 0x14 returns 0xCA so bits 5,4,3 are 001 which is undefined according page 54 of the datasheet not 011:BQ25890 or 000:BQ25892.

And bits 1,0 are 10 which is also undefined as the Device Revision: 01.

Any suggestions as to where I might be going wrong?

over 7 years ago

0 Joel Hernandez II over 7 years ago

TI__Mastermind 25800 points

Hey Ben,

Can you post all of your read values?

Regards,
Joel H

0 Ben Pitcairn over 7 years ago in reply to Joel Hernandez II

Prodigy 40 points

Reg 00 Data 0xB5 10110101
Reg 01 Data 0x5B 01011011
Reg 02 Data 0x90 10010000
Reg 03 Data 0xFC 11111100
Reg 04 Data 0x01 00000001
Reg 05 Data 0x50 01010000
Reg 06 Data 0x32 00110010
Reg 07 Data 0xC0 11000000
Reg 08 Data 0xFF 11111111
Reg 09 Data 0xC0 11000000
Reg 0A Data 0xBD 10111101
Reg 0B Data 0x8F 10001111
Reg 0C Data 0x48 01001000
Reg 0D Data 0xC5 11000101
Reg 0E Data 0x00 00000000
Reg 0F Data 0xD4 11010100
Reg 10 Data 0x1C 00011100
Reg 11 Data 0x1B 00011011
Reg 12 Data 0x19 00011001
Reg 13 Data 0xEA 01110101
Reg 14 Data 0xCA 11001010
Readings past the last register
Reg 15 Data 0xFE 11111110
Reg 16 Data 0x01 00000001
Reg 17 Data 0x4A 01001010
And so on

Reg 21-25 are all 0x00

Reg 26-27 0xFF

Reg 30 and above are all 0x00

0 Joel Hernandez II over 7 years ago in reply to Ben Pitcairn

TI__Mastermind 25800 points

Hey Ben,

Have you attempted to communicate with the EVM using bqStudio to see if you get similar results?
In bqStudio, you can use the "Advanced Comm" tab to try single reads and multi-reads using bqStudio's pre-built I2C protocol for the device.

What is strange is that you are reading more registers than what is allowed for the device. (i.e. Reg15-17).

Do you have external pull-ups on your microcontroller board in addition to the ones that are on the EVM? And if you are only using the EVM's pullups, is JP4 jumper connected to a valid source (VSYS if you have no battery connected).

I suggest you apply single write to REG14[7] = 1 to reset all the registers, and then attempt to single read each register without writing values.

Please make sure that you are following the I2C protocol described in section 9.2.16 of the bq25892 datasheet. That section also describes implementation of either single reads or multi-reads. Not sure which you are performed, if not both.

Regards,
Joel H

0 Ben Pitcairn over 7 years ago in reply to Joel Hernandez II

Prodigy 40 points

I do not have the EV2300 module so I haven't used the bqStudio software.
I am using pull-ups on my microcontroller board for the i2c bus - so I don't have the pull-up jumper set.

I tried writing to REG_RST but it made no difference - however if you look at the data read from REG14 the REG_RST bit is already set.

I have only been performing single byte reads (and writes) for now. I'm confident I'm following the protocol correctly but I can send you a capture from my logic analyser if that would help.

Regards,

Ben