MSP430F2272: DCO cablibration without external crystal.

Wayne Jeong97575

Part Number: MSP430F2272

Hello.

I am using DCO without external crystal at MSP430F2272.

Timer times are different for each product and there is a big difference between the tolerances when I measured SMCLK out for each MCUs.

The example code to calibrate DCO on the web is needed external clock but my board is not connected with external crystal.

Is there a way to calibrate a DCO without an external crystal?

Thank you

over 4 years ago

0 Bruce McKenney47378 over 4 years ago

Guru 88550 points

The F2272 has 4 sets of DCO calibration constants in InfoA flash [Ref Data Sheet (SLAS504G) Table 14]. Have you tried them?

0 Wayne Jeong97575 over 4 years ago in reply to Bruce McKenney47378

Intellectual 685 points

Yes, I already know about that.

And I set it as follows.

BCSCTL1 = CALBC1_8MHZ;

DCOCTL = CALDCO_8MHZ;

thank you.

0 Wayne Jeong97575 over 4 years ago in reply to Wayne Jeong97575

Intellectual 685 points

Hello.

I would like another opinion.

Thank you.

0 Gary Gao over 4 years ago in reply to Wayne Jeong97575

TI__Mastermind 32545 points

Hi Wayne

Have you see the difference of the frequency is meet the parameters showed in the chapter named "DCO Frequency" of its datasheet http://www.ti.com/lit/ds/symlink/msp430f2272.pdf

If you don't want to use the FACTORY-PROGRAMMED DCO CALIBRATION CONSTANTS in the TLV, you should find a reference clk first to do the calibration. You can use the demo online and use the VLO sourced ACLK as the reference clock. But you know, the accuracy of the VLO is not good.

Best regards

Gary

**Attention** This is a public forum

MSP low-power microcontrollers

MSP low-power microcontroller forum

MSP430F2272: DCO cablibration without external crystal.