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On 11/01/2026 16:15, Single Stage to Orbit wrote:
> Hi chaps
> 
> Does this group also include the Raspberry rp2040/rp2350 as well? I'm
> in need of resources or the knowledge of how to program the PWMs on the
> rp2040. If not, are there any online resource I can consult.
> 
I certainly have been playing with these in a C context.

I klooked into PWM in some detail but have not yet implemented it.

> The rp2040 datasheets are instrutable on the subject of the PWMs. I can
> easily blink an ordinary LED, likewise for a RGB LED via three GPIO
> pins, but for doing cool tricks like fading/brightening the separate
> RGB components on a RGB LED it's beyond me, I think PWMs are needed for
> this but all I could find was micropython stuff and that works but I'd
> like to know how to do it baremetal with ARM thumb assembly.
> 
Cant help with assembly, only C.

IIRC there are a couple of places you just wrote data to to set the 
thing up and these can be rewritten live to vary the pulse width

Easy way to do that is to run a sleep_ms(loop) and every iterations 
change something for a fade up down.

From: 
https://www.raspberrypi.com/documentation/pico-sdk/hardware.html
group_hardware_pwm


The RP2040 PWM block has 8 identical slices, the RP2350 has 12. Each 
slice can drive two PWM output signals, or measure the frequency or duty 
cycle of an input signal. This gives a total of up to 16/24 controllable 
PWM outputs. All 30 GPIOs can be driven by the PWM block.

The PWM hardware functions by continuously comparing the input value to 
a free-running counter. This produces a toggling output where the amount 
of time spent at the high output level is proportional to the input 
value. The fraction of time spent at the high signal level is known as 
the duty cycle of the signal.

The default behaviour of a PWM slice is to count upward until the wrap 
value (pwm_config_set_wrap) is reached, and then immediately wrap to 0. 
PWM slices also offer a phase-correct mode, where the counter starts to 
count downward after reaching TOP, until it reaches 0 again.

// Output PWM signals on pins 0 and 1

#include "pico/stdlib.h"
#include "hardware/pwm.h"

int main() {

     // Tell GPIO 0 and 1 they are allocated to the PWM
     gpio_set_function(0, GPIO_FUNC_PWM);
     gpio_set_function(1, GPIO_FUNC_PWM);

     // Find out which PWM slice is connected to GPIO 0 (it's slice 0)
     uint slice_num = pwm_gpio_to_slice_num(0);

     // Set period of 4 cycles (0 to 3 inclusive)
     pwm_set_wrap(slice_num, 3);
     // Set channel A output high for one cycle before dropping
     pwm_set_chan_level(slice_num, PWM_CHAN_A, 1);
     // Set initial B output high for three cycles before dropping
     pwm_set_chan_level(slice_num, PWM_CHAN_B, 3);
     // Set the PWM running
     pwm_set_enabled(slice_num, true);

     // Note we could also use pwm_set_gpio_level(gpio, x) which looks 
up the
     // correct slice and channel for a given GPIO.
}

Now that references a  c library, but easy enough to pull assembler 
source out of it


> Many thanks,
> Alex

-- 
?It is dangerous to be right in matters on which the established 
authorities are wrong.?

? Voltaire, The Age of Louis XIV


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