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Showing results for tags 'DCO'.
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Just as an FYI - I was concerned about using the built in DCO in the FR5969 for UART because the spec sheet says although it's factory trimmed, it's still +/-3.5%. Generally it needs to be within 2% for a UART to work correctly so I measured the two FR5969's I have on our 2.4GHz frequency counter and this is what I got. 2 is obviously not a big sample size, but the frequency trimmed DCO on the FR series looks pretty good @ room temp and 8MHz or under. I found another doc from TI that's a comparison between F5xxx and FR5xxx and it mentions the DCO is generally within 2% "within a restricted temperature range" and within 3.5 in the full temperature range (-40C to 85C). I may need to re-measure at 4C because that's typically where our project will be operating.
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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
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Hi guys, I just noticed that the errata files for the value line were updated on 17th January. The new files contain a revision to the BCL12 text, adding the following advice: "In the majority of cases switching directly to intermediate RSEL steps as described above will prevent the occurrence of BCL12. However, a more reliable method can be implemented by changing the RSEL bits step by step in order to guarantee safe function without any dead time of the DCO." Might be of interest if you've been getting DCO lockups as I have recently!
