BQ40Z50: Extra byte in Manufacture Block Access not detailed in technical reference manual.

Ian Aherne

Part Number: BQ40Z50
Other Parts Discussed in Thread: BQSTUDIO

Can you confirm if the following is correct from the BQ40Z50 Technical reference.

From looking at a logic analyzer trace when using bqStudio with the Bq40Z50 evaluation board an extra byte is sent between 0x44 and data sent/ data read, the extra byte is the number of bytes in data sent/data read.

From what I can see(and please correct me if I'm wrong) this information is missing from the technical reference manual see analyzer trace below of sending chemical ID command to bq40z50.

Regards

Ian

over 3 years ago

+1 Jackson DiGiovanna over 3 years ago

TI__Expert 8315 points

Ian,

We follow SMBus protocol and have a link to this protocol in the TRM. This extra byte is on write commands only so the gauge knows how many bytes need to be written.

We will also update the TRM to more clearly reflect this info though.

Thanks and let me know of any further questions,

Jackson

0 Ian Aherne over 3 years ago in reply to Jackson DiGiovanna

Prodigy 200 points

Thanks Jackson

For clarity,

The standard commands (word) don't use the extra byte for data size.

Manufacture Block Access use the extra size byte for both reads and writes.

The TRM update would be helpful for future developers, from reading other threads I am not the first person to highlight this issue.

Regards

Ian

0 Steven(Shenzhen) Shi over 3 years ago in reply to Jackson DiGiovanna

TI__Mastermind 30515 points

Hi Jackson,

My customer also encountered this issue. They need to add byte numbers to write the command otherwise the command won't be write into the gauge.

However, when I used BQstudio to check the result I didn't add byte numbers but the write was successful. So the difference is due to our BQstudio tool?

0 Jackson DiGiovanna over 3 years ago in reply to Steven(Shenzhen) Shi

TI__Expert 8315 points

Steven,

For write commands in BQ Studio you will not need to specifically specify the byte number to write as it is inferred from what you put in the write block. Here for example you put 54 0B so it knows to only write the first 2 bytes. If you wrote more bytes in this text box I would expect it to change other values as well. For read commands, specifying a byte number to read should be irrelevant as it should read the entire block.

Let me know if you have any other questions,

Jackson

0 Steven(Shenzhen) Shi over 3 years ago in reply to Jackson DiGiovanna

TI__Mastermind 30515 points

Hi Jackson,

Thanks a lot. This solved my issue.

BR,

Steven

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BQ40Z50: Extra byte in Manufacture Block Access not detailed in technical reference manual.