Pio last update #4212
Pio last update #4212
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@mateir-7 can you fix the following clippy lint?
error: unused import: `kernel::hil::pwm::Pwm`
--> boards/pico_explorer_base/src/main.rs:23:5
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23 | use kernel::hil::pwm::Pwm;
| ^^^^^^^^^^^^^^^^^^^^^
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= note: `-D unused-imports` implied by `-D warnings`
= help: to override `-D warnings` add `#[allow(unused_imports)]`
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Can you explain a little bit more the problem and the fixe's limitations? |
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Fixed the clippy lint - just forgot to commit yesterday, didn't understand why it failed. About the 3 times lower frequency, I honestly have no idea why that is happening? Only thing that comes to mind is the resistor I used to test it, maybe that could interfere with it? Values over 1 MHz don't work because of how PWM is coded in pioasm. In PIO, the program reads the number of loops that it needs to go through for one PWM cycle and then reads at what loop it is supposed to turn the signal on. This means that the HIGHER the number of loops, the more time it takes for one PWM cycle, meaning LESS frequency. This leads to higher frequencies needing lower number of loops, and at one point the number of loops the program goes through is so low that it can't properly divide it for the exact duty cycle needed. This leads to duty cycles being off. Frequency starts getting off little by little as the value goes higher (most likely) due to the assembly program having 3 clock cycles at the beginning just to get its data and another cycle when it needs to turn on the led, leading to more noticeable "time loss" at higher frequencies. At 1000 cycles, the 4 extra won't be a problem, but at 100 or less cycles it could lead to that - 1 MHz, for example, has 125 cycles. |
Pull Request Overview
Modified main.rs so pio_pwm doesn't always start + observed with oscilloscope that values under 1 MHz were 3 times as low as they needed to be, fixed.
Note: values over 1MHz do exist but frequency and duty cycle will not be the same as the input ones.
Testing Strategy
This pull request was tested by running the now commented pio_pwm.start function at the end of the main.rs file.
TODO or Help Wanted
No help needed.
Documentation Updated
/docs, or no updates are required.Formatting
make prepush.