AFE4404: Calibration_AFE4404.c BLOCK_SIZE & BLOCK_SIZE_BITS value

kim minseo

Intellectual 400 points

Part Number: AFE4404

Hi.

I was looking at the Calibration_AFE4404.c code and I had a question.

In Calibration_AFE4404.c, it is declared BLOCK_SIZE = 8, BLOCK_SIZE_BITS = 3.

Is there any problem if I change it to BLOCK_SIZE = 16, BLOCK_SIZE_BITS = 4?

Additionally, may I know why BLOCK_SIZE = 8 is set?

Thank you.

over 1 year ago

0 Praveen Aroul over 1 year ago

TI__Mastermind 47616 points

Hi Kim,

Yes, you can change the block size to 16. Increasing the block size would only increase the calibration convergence time.

We felt 8 samples should be sufficient for calculating the average.

0 kim minseo over 1 year ago in reply to Praveen Aroul

Intellectual 400 points

Hi.

Thank you for your reply.

Then is there no problem if I change BLOCK_SIZE to 16 and use BLOCK_SIZE_BITS as 3?

Thank you.

0 kim minseo over 1 year ago in reply to Praveen Aroul

Intellectual 400 points

Hi.

I have an additional question.

ADC_CODE_AMB_DAC_STEP = 65000;

Can you explain why this value is 65000? Is it related to MSP430?

Thank you.

0 Praveen Aroul over 1 year ago in reply to kim minseo

TI__Mastermind 47616 points

Kim,

Yes, block size and block size bits should be related as powers of 2.

0 Praveen Aroul over 1 year ago in reply to Praveen Aroul

TI__Mastermind 47616 points

Kim,

Ideally the ambient dac step code will be 87381 for the ambient dac step current of 0.5uA and for TIA gain of 50k.

But realistically, the ambient dac current is 0.47uA and there is 20% variation on the ambient dac current and the tia gain.

Hence we used a value of 65k. You may want to run a pre-calibration routine to find out the adc code for the ambient dac step for every device and use that value in the calibration routine.

0 kim minseo over 1 year ago in reply to Praveen Aroul

Intellectual 400 points

Hi.

Thank you for reply

Then, if ADC_CODE_AMB_DAC_STEP arbitrarily modifies this variable and proceeds with the test, will there be a problem?

Thank you.

0 Praveen Aroul over 1 year ago in reply to kim minseo

TI__Mastermind 47616 points

Kim,

The ADC_CODE_AMB_DAC_STEP value will be unique to each device. If calculated correctly, this shouldn't cause any problem.

Data converters

Data converters forum

AFE4404: Calibration_AFE4404.c BLOCK_SIZE & BLOCK_SIZE_BITS value