SETUP DEVICE TREE FILE

Các giá trị cần biết khi config một timer

device tree
Name	Type	Details
`reset`	`phandle-array`	Pin configuration/s for the first state . Content is specific to the selected pin controller driver implementation.
`st,prescaler`	`int`	Clock prescaler at the input of the timer Could be in range [0 .. 0xFFFF] for STM32 General Purpose Timers (CLK/(prescaler+1) )
`st,countermode`	`int`	Sets timer counter mode. Use constants defined in dt-bindings/ timer/stm32-timer.h. STM32_TIM_COUNTERMODE_UP: used as up counter. STM32_TIM_COUNTERMODE_DOWN: used as downcounter. STM32_TIM_COUNTERMODE_CENTER_DOWN: c ounts up and down alternatively. Output compare interrupt flags of output channels are set only when the counter is counting down. STM32_TIM_COUNTERMODE_CENTER_UP: counts up and down alternatively. Output compare interrupt flags of output channels are set only when the counter is counting up. STM32_TIM_COUNTERMODE_CENTER_UP_DOWN: counts up and down alternatively. Output compare interrupt flags of output channels are set only when the counter is counting up or down.
`reset-names`	`string-array`	Name of each reset

Device tree for timer

Đoạn code dưới đây là một ví dụ cho việc viết device tree cho TIM2, với chức năng là PWM

&timers2 {
   status = "okay";

   pwm2: pwm {
      status = "okay";
      pinctrl-0 = <&tim2_ch1_pa0>;
      pinctrl-names = "default";
   };
};

Tương tự với ví dụ với TIM3, với presclaer = 10000, PWM tại PB4

&timers3 {
   st,prescaler = <10000>;
   status = "okay";

   pwm3: pwm {
      status = "okay";
      pinctrl-0 = <&tim3_ch1_pb4>;
      pinctrl-names = "default";
   };
};

Config timer in Kconfig

CONFIG_PWM=y

CONFIG_LED=y

CONFIG_STDOUT_CONSOLE=y
CONFIG_PRINTK=y
CONFIG_LOG=y