BQ27426: Basics of reading on I2C

Darren Jenkins

Part Number: BQ27426

Tool/software:

Gauge team,

Can you outline the steps involved in reading the Device Type from the Control Register? I thought it would be something like the steps below, but the customer keeps getting 0000.

S 55W A 00 A 00 A 01 NP <- Write the Standard Command 0x00, Set the Control Subcommand to 0x0001

S 55W A 00 A Sr 55R A 04 A 21 NP <- Read the Control register, Device Type

Where:

55W = AA

55R = AB

Here's what they see (SDA yellow, SCL purple):

Thanks,
Darren

over 1 year ago

0 Jonny over 1 year ago

TI__Mastermind 26571 points

Hello,

I recommend referring to the TRM for an example of I2C read and write with the BQ27426.

Regards,

Robert.

0 Darren Jenkins over 1 year ago in reply to Jonny

TI__Genius 12801 points

Hi Robert,

I see two differences. The byte order is LSB, MSB. So the subcommand should be the other way around. And the TRM section 4.1 shows the process to Unseal. The TRM doesn't actually state which registers are protected by the Seal and Unseal process.

Not sure if this will help. I'll update here if it does.

Darren

0 Darren Jenkins over 1 year ago in reply to Darren Jenkins

TI__Genius 12801 points

Hi Robert,

The customer changed the byte order in the interaction, and it didn't help.

S 55W A 00 A 01 A 00 NP <- Write the Standard Command 0x00, Set the Control Subcommand to 0x0001

S 55W A 00 A Sr 55R A 21 A 04 NP <- Read the Control register, Device Type

He even tried doing the unseal procedure at the start, and it made no difference.

Can you review the I2C interaction above please and let me know what is wrong?

Thanks,
Darren

0 Darren Jenkins over 1 year ago in reply to Darren Jenkins

TI__Genius 12801 points

Robert, you can ignore this follow up question. The issue seems to be resolved.

Darren

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BQ27426: Basics of reading on I2C