mahler.jp Programming Tips Blog

はじめに

　表題の通り、Raspberry Pi PicoとC言語でローテーションサーボモータSG-90HVを回してみました。
　PWM周波数とパルス幅の指定で回せられればよいのですが、それができないのと、デューティ比の計算にシステムクロックが係ってきているのが面倒です。
　ますはCソースコードです。

pwm01.c

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

int main() {
    /// \tag::setup_pwm[]

    // 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 0.02s 
    pwm_set_wrap(slice_num, 24999);
    pwm_set_clkdiv(slice_num, 100.0);
    // Set channel A Duty
    pwm_set_chan_level(slice_num, PWM_CHAN_A, 2315);
    // Set initial B Duty
    pwm_set_chan_level(slice_num, PWM_CHAN_B, 1330);
    // Set the PWM running
    pwm_set_enabled(slice_num, true);
    /// \end::setup_pwm[]

    //Start  ESC Calibration
    sleep_ms(2000);
    pwm_set_chan_level(slice_num, PWM_CHAN_A, 1330);
    sleep_ms(5000);
    //End Start  ESC Calibration

    while(true){
      // Duty cycle = (1500 us / 20000 us) * (wrap + 1) = 0.075 * 25000 = 1875
      pwm_set_chan_level(slice_num, PWM_CHAN_A, 1875);
      sleep_ms(2000);
      // Duty cycle = (2000 us / 20000 us) * (wrap + 1) = 0.1 * 25000 = 2500
      pwm_set_chan_level(slice_num, PWM_CHAN_A, 2500);
      sleep_ms(2000);
      // Duty cycle = (1500 us / 20000 us) * (wrap + 1) = 0.075 * 25000 = 1875
      pwm_set_chan_level(slice_num, PWM_CHAN_A, 1875);
      sleep_ms(2000);
      // Duty cycle = (1000 us / 20000 us) * (wrap + 1) = 0.05 * 25000 = 1250
      pwm_set_chan_level(slice_num, PWM_CHAN_A, 1250);
      sleep_ms(2000);
    }
}

CMakeLists.txt

　続いて、CMakeLists.txtです。

#Set the mimum required version of CMake
cmake_minimum_required(VERSION 3.12)

#Pull in SDK (must be before project)
include(pico_sdk_import.cmake)

#Set the project name, the programming language
project(pwm01 C CXX ASM)
set(CMAKE_C_STANDARD 11)
set(CMAKE_CXX_STANDARD 17)

#Initialize the SDK
pico_sdk_init()

#Add an executable target to be build from the source files
add_executable(pwm01 pwm01.c)

#Pull in our pico_stdlib which aggregates commonly used features
target_link_libraries(pwm01 pico_stdlib)
target_link_libraries(pwm01 hardware_pwm)

#Create map/bin/hex/uf2 file etc.
pico_add_extra_outputs(pwm01)