Use same USB_PLL default setting as the C SDK #688
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The previously used settings used a VCO clock of 480MHz, which is outside the valid range (750MHz - 1600MHz) given by the datasheet since revision 1.8. There are several valid VCO values, and there is a tradeoff between lower jitter and lower power consumption. So it's not obvious which value would be the best default. Instead of doing our own guesswork, use the same value as the C SDK: https://github.com/raspberrypi/pico-sdk/pull/869/files This patch only changes the default value, but doesn't update the input validation. So it's still possible to manually specify a VCO frequency outside the updated range, as long as it's in the more lenient range specified by older datasheet revisions, 400MHz - 1600MHz.
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This completes the change introduced in #688 to update the valid range for VCO’s frequency. Note: this change was left off until now because it was a breaking change.
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The previously used settings used a VCO clock of 480MHz, which is outside the valid range (750MHz - 1600MHz) given by the datasheet since revision 1.8.
There are several valid VCO values, and there is a tradeoff between lower jitter and lower power consumption. So it's not obvious which value would be the best default.
Instead of doing our own guesswork, use the same value as the C SDK: https://github.com/raspberrypi/pico-sdk/pull/869/files
This patch only changes the default value, but doesn't update the input validation. So it's still possible to manually specify a VCO frequency outside the updated range, as long as it's in the more lenient range specified by older datasheet revisions, 400MHz - 1600MHz.