Raspberry Pico running at 200MHz - non-standard

[Gustavomurta]

When testing my Raspberry Pico boards, I found that they were all set to 200 MHz when I compile Tinygo programs.

I identified this change in Tinygo:
#4768

The Pico's default system clock frequency is 125 MHz.

Is it possible in Tinygo to select this frequency during compilation?

[Gustavomurta]

I recently developed this program to configure the Pico System Clock:

Adjusting the RP2040 system clock (for 125 MHz) with just 8 lines of code!
https://github.com/orgs/tinygo-org/discussions/4940#discussioncomment-13799825

[eliasnaur]

Note that RPi certified the rp2040 to run at 200MHz with an elevated core voltage. The datasheet states:

You can achieve 200MHz by running at an elevated core supply (DVDD) and setting VREG VSEL to 1.15V.

See also the picosdk release notes under "200Mhz Clock Support for RP2040".

That said, is there a reason to offer a 125MHz option?

[Gustavomurta]

Hi eliasnaur,
When you purchase a Pico board, it comes with a 125 MHz clock, right? In my opinion, the 200 MHz clock could be optional.

In my case, my test applications depend on the clock frequency. Therefore, I've already developed the program to change the clock. So this 200 MHz option is up to the Tinygo developers. Thank you.

[eliasnaur]

I don't know what you mean by "comes with a 125MHz clock". The clock speed is configurable by software, and if anything, the maximum clock speed was 133MHz before being bumped to 200MHz.

Perhaps by "comes with a 125MHz clock" you mean that TinyGo used to run Pico boards at 125MHz and now runs them at a different speed. That's true, but I don't think it's reasonable to expect machine.CPUFrequency to remain constant between rebuilds (for the same reason you can't expect runtime.NumCPU to stay constant - and indeed the latest TinyGo did bump rp2040's runtime.NumCPU to 2).

That leaves the question whether changing clock speeds should be offered as an option. Do you have a compelling use case for such an option?

[Gustavomurta]

Dear Eliasnur,
Just for reference, the Arduino-pico IDE (earlephilhower) offers numerous CPU clock options. Just a suggestion.

https://github.com/earlephilhower/arduino-pico

My projects involve data capture at various speeds, including extreme overclocking.

[xudongzheng]

That said, is there a reason to offer a 125MHz option?

I have a custom RP2040 board though I'm building with -target pico. I imagine I'm not the only one doing this with a custom board.

With CPU frequency set to 200MHz, "hello world" doesn't even run. It seems to be fine at 150MHz, 160MHz is where it breaks. There is a hard fault according to GDB:

[rp2040.core0] clearing lockup after double fault
[rp2040.core0] halted due to debug-request, current mode: Handler HardFault
xPSR: 0x60000003 pc: 0xfffffffe msp: 0x200007e0

If I want to keep 200MHz, I can alternatively change BOARD_PICO_FLASH_SPI_CLKDIV from 2 to 4.