RP2040 USB PLL settings

Question

RP2040 USB PLL settings

Closed this issue a year ago · 3 comments

I was reading the RP2040 initialization code in src/rp2040/hardware.s and noticed something: the USB PLL is configured for a VCO frequency of 480 MHz. The RP2040 data sheet says the VCO frequency is supposed to be between 750 and 1600 MHz.
I have not seen problems from this, but I wonder if it would make sense to change the code to conform to the data sheet requirements. For example, doubling the PLL frequency would do, that would mean PLL_FBDIV would be 80 rather than 40, and PLL_POSTDIV2 would be 4 rather than 2.

Answer 1 · 2023-12-13T16:40:59.000Z

Thanks for catching this! I overlooked this when I got the code from its original author. I will make the changes when I come home from work today.

Answer 2 · 2023-12-14T02:15:37.000Z

I have fixed this issue, and you can get the latest, build 1.3.3.2, from here.

Answer 3 · 2023-12-16T18:43:00.000Z

Looks good, thanks!