Yet another DCO calibrator

[David Bender 28]

This DCO calibrator starts with me not having a crystal on my board, and stealing rick's idea about using the UART to calibrate the DCO. It works without the UART peripheral or capture compare. The host sends the 'U' character and the micro responds with what adjustment it made, or that it calibrated to the target frequency. When the micro is calibrated, it sends the calibration constant values to the host, which prints them for the user. I used an oscope to verify the frequency on the P1.4's SMCLK output.

 

Code is here:

https://github.com/analog10/UART_DCO_Calibrator

 

rick's original concept is here:

https://github.com/RickKimball/msp430_code/blob/master/fabooh/examples/serial/dco_calibrate/goldilocks.cpp

[tingo 22]

This is handy to have - thanks!

[bluehash 1,581]

This DCO calibrator starts with me not having a crystal on my board, and stealing rick's idea about using the UART to calibrate the DCO. It works without the UART peripheral or capture compare. The host sends the 'U' character and the micro responds with what adjustment it made, or that it calibrated to the target frequency. When the micro is calibrated, it sends the calibration constant values to the host, which prints them for the user. I used an oscope to verify the frequency on the P1.4's SMCLK output.

 

Code is here:

https://github.com/analog10/UART_DCO_Calibrator

 

rick's original concept is here:

https://github.com/RickKimball/msp430_code/blob/master/fabooh/examples/serial/dco_calibrate/goldilocks.cpp

 @@David Bender, Do you have a link to @@Rickta59 's idea or was it on IRC

Very good idea BTW.

[David Bender 28]

I just googled enough to find goldilocks.cpp, I can't really provide a link beyond that.

[oPossum 1,083]

I don't think Rick posted it here.

 

I did something similar for AVR and MSP430:

 

http://forums.adafruit.com/viewtopic.php?f=24&t=5078

 

http://forum.43oh.com/topic/1375-characterize-dco-without-32768-khz-xtal/

[Rickta59 589]

It wasn't my idea. I think I first noticed the concept in an ATMEL application note:

 

http://www.atmel.com/Images/doc2555.pdf

 

I've also liked @oPossums solution. However that is geared towards CCS and CCS asm.

 

My main purpose was to provide a simple example that combined timers and fabooh's serial implementation. And more importantly to provide an answer to g0rdon's IRC question.

 

-rick

[David Bender 28]

Updated the utility so the clock speed can be specified at run time (rather than compiled into FW). Convergence is also much faster.