Add on-chip voltage regulator (VREG) voltage setting function #757
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PR sent to rp2040-pac. |
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The core voltage is now changed using VSEL_A, which was added in pac v0.6.0. It is a trivial code, but I think it makes sense as a variation of the example and on-target-tests. |
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| fn change_onchip_regulator_voltage(state: &mut State) { |
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How do we know that this test works reliably on every device?
The datasheet says: "Note that RP2040 may not operate reliably with its digital core supply (DVDD) at a voltage other than 1.1V."
Perhaps this test should only cover a smaller range of voltages, eg. 1.05 - 1.15V?
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In my experience, I have set the core voltage to 1.2V on more than 50 RP2040s and have never had a problem. Also, in the thread about overclocking on the RP2040, there is no example of a failure to increase the core voltage.
However, this is not normal usage, there is no guarantee that it will work reliably on all RP2040s.
I noticed that with the default system clock, lowering the core voltage too much can cause problems. It should be a smaller test case range, as you mentioned. Especially in the direction of lowering the core voltage.
1.20V should be fine, so i'll reduce it to 1.05 - 1.20V.
If you are concerned, I would reduce it more. Reducing it is easy:)
Fix doc test for vreg_set_voltage() Rename vreg_set/get_voltage() to set/get_voltage()
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Reduced test cases and improved documentation comments. And rebased commit log to tidy it up. |
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As one might expect from the slope of this graph, 0.80V may not work at the default system clock frequency. However, the RP2040 C/C++ SDK has a minimum voltage of 0.85V, so 0.80V seems like an unusual value. |
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What I mean is that the tests as implemented there do not provide anyproof that things are:
Writing to and Reading from a register is trivial enough that I don’t think it requires an on-target tests. For example, if there’s a possibility to actually verify that the voltage is applied as expected that would make a good test case. |
With the Raspberry Pi Pico, that is impossible. |
Added an on-chip voltage regulator voltage setting function.
Increasing core voltage may be necessary for overclocking. Implemented with reference to hardware_vreg in pico-sdk.