MSP430F67791A: Crystal Selection

PRASIDDHNATH YADAV

We are using Ti controller series MSP430F67791A in our Protection relay device .I have already connected a crystal of 32.768kHz with Load Capacitance of 15pF and generated ADC interrupt of 1ms to collect ADC sample in every 1 ms. But due to accuracy concern we could not able to collect the each sample in 1 ms duration.
Some time it collect in 2ms , 1.3, 0.980 , 0.550 & 0.002. Which affect our measurement magnitude & relay operating time value. Hence forth we would like to use 8.00MHz crystal with same controller is it feasible to configure the clock initialization and ADC interrupt using 8.00MHz crystal.
If so, then what are the parameters alongwith parameter values that we need to be taken into consideration???
We are waiting for your quick response which will help us to move forward.

Thanks & Regards.
Kaustubh Gawli

over 4 years ago

0 Cash Hao11 over 4 years ago

TI__Mastermind 46765 points

Hi,

Which ADC you are referring here in the MSP430F67791A? The 10bit SAR ADC or the 24bit SD ADC?

It seems that you need a higher ADC sampling frequency. You can use a higher frequency clock source for the ADC to achieve that.

The clock source for the 10bit SAR ADC are SMCLK, MCLK, ACLK and MODCLK. The clock source for the 24bit SD ADC are SMCLK, MCLK, ACLK and external CLK. You can check your configuration and use a higher frequency.

Best regards,

Cash Hao

0 PRASIDDHNATH YADAV over 4 years ago in reply to Cash Hao11

Prodigy 50 points

Hi Cash Hao,

We are using 24bit SD ADC with SMCLK clock. But by using external clock (32kHz) we configure SMCLK for 24 Bit SD ADC for 1ms ADC interrupt.

We would like to know that by using external clock at 8Mhz can we achieve higher frequency.

Regards,

Kaustubh Gawli

0 Cash Hao11 over 4 years ago in reply to PRASIDDHNATH YADAV

TI__Mastermind 46765 points

Hi,

Since you are using the SMCLK as the SD24 ADC's clock source. Why not just configure the SMCLK to 8MHz in the code? It is not necessary to use an external 8MHz clock source.

Her is an example code of how to configure the SMCLK to 8MHz. https://dev.ti.com/tirex/explore/node?node=AOSlnOtV9.J1XfyQfN.cYw__IOGqZri__LATEST

Best regards,

Cash Hao

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MSP430F67791A: Crystal Selection