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YuzukiNeko

PWM-BL - 模拟背光

PWM_BL 是 F101 上专门驱动 LCD 背光的模块，和通用的 PWM 是两个独立的设备。它不产生任意频率的方波：它控制片内的两个升压（BOOST）电路，通过“灌电流”的大小调节背光 LED 的亮度，调光有数字加模拟两种方式。在 Zephyr 里它是 pwm_bl 设备，接口仍然是标准的 <zephyr/drivers/pwm.h>，驱动是 drivers/pwm/pwm_sunxi_bl.c。

项目内容
端口两个：端口 0（BOOST0，PWM 脚 PB2，反馈脚 PB3）数字加模拟比较调光；端口 1（BOOST1，PWM 脚 PB0，反馈脚 PB1）纯模拟，750 kHz
通道对 API 只有一个通道，通道 0，别的通道返回 -EINVAL；设置时两个端口一起开关，亮度（灌电流）只写端口 0
亮度脉宽 × 256 ÷ 周期 得到灌电流级别，最大 200，0 关闭
计时单位pwm_get_cycles_per_sec 返回 1 GHz，一个周期是 1 ns，比例精确
极性没有。模拟级没有极性，flags 被忽略
周期周期的长短不改变输出，只有脉宽和周期的比值有用
板子f101_evb 的 RGB 屏背光接在这里；yuzukineko 的背光在通用 PWM 的通道 2，不用 PWM_BL

本文的演示在 yuzukineko 上运行：用 overlay 把 pwm_bl 打开（只用 PB2、PB3，不动 PB0、PB1 的控制台），这块板上没有接 PWM_BL 的背光，所以演示读回模块的寄存器来看驱动写进去的亮度，没有测输出。

设备树

Section titled “设备树”
文件作用
dts/bindings/pwm/allwinner,sunxi-pwm-bl.yaml绑定
dts/riscv/allwinner/sun252i_f101.dtsiSoC 设备树：pwm_bl 节点，默认 disabled
examples/pwm_bl_api/app.overlay应用的 overlay：引脚组，打开 pwm_bl，用 zephyr,user 节点引用它

SoC 设备树：sun252i_f101.dtsi

Section titled “SoC 设备树：sun252i_f101.dtsi”
pwm_bl: pwm@200a000 {
  /* 匹配驱动 pwm_sunxi_bl.c 里的 DT_DRV_COMPAT allwinner_sunxi_pwm_bl */
  compatible = "allwinner,sunxi-pwm-bl";


  /* 引用它的 pwms 属性有 3 个格子：通道、周期（纳秒）、标志 */
  #pwm-cells = <3>;


  /* 寄存器窗口：基址 0x0200a000，长度 0x400；两个端口各占 0x200 */
  reg = <0x0200a000 0x400>;


  /* 驱动自己配置时钟：CCU 的基址，PWM_BL 模块时钟、总线门控和复位寄存器的偏移 */
  ccu-base = <0x02001000>;
  mod-clk-reg = <0x790>;
  bus-clk-reg = <0x794>;


  status = "disabled";
};

打开 PWM_BL：app.overlay

Section titled “打开 PWM_BL：app.overlay”

yuzukineko 的板级文件没有打开 pwm_bl，演示用应用的 overlay 打开它。PB0、PB1 是 UART1 控制台，不能给 PWM_BL，所以只给 PB2、PB3（BOOST0 的 PWM 和反馈，复用功能 2），再用 zephyr,user 节点放一个 pwms 属性：

/*
 * The PWM_BL block is not used by the yuzukineko board (its panel backlight is on PWM channel 2).
 * It is switched on here for the demonstration, on PB2 (PWM) and PB3 (FB) of the first boost
 * converter, and not on PB0/PB1, which carry the console.
 */
&pio {
  pwm_bl_pins_app: pwm_bl_pins_app {
    pwm_bl_group {
      pinmux = <ALLWINNER_PINMUX(ALLWINNER_PIO_PB, 2, 2)
          ALLWINNER_PINMUX(ALLWINNER_PIO_PB, 3, 2)>;
    };
  };
};


&pwm_bl {
  status = "okay";
  pinctrl-0 = <&pwm_bl_pins_app>;
  pinctrl-names = "default";
};


/ {
  zephyr,user {
    /* channel 0, period 20 us, like the backlight node of the f101_evb board */
    pwms = <&pwm_bl 0 20000 PWM_POLARITY_INVERTED>;
  };
};

PWM_POLARITY_INVERTED 写在这里只是和别的背光节点保持一致，对 PWM_BL 没有影响。显示流水线用的 pwm-backlight 节点的属性见 显示 和 PWM。

绑定：allwinner,sunxi-pwm-bl.yaml

Section titled “绑定：allwinner,sunxi-pwm-bl.yaml”
# Copyright (c) 2026 Yuzuki Tsuru
# SPDX-License-Identifier: Apache-2.0


description: |
  Allwinner PWM_BL backlight controller (digital dimming + analog current
  sink). Single logical channel 0; the duty is mapped to a load current
  reference.


compatible: "allwinner,sunxi-pwm-bl"


include: [pwm-controller.yaml, pinctrl-device.yaml, base.yaml]


properties:
  reg:
    required: true


  "#pwm-cells":
    const: 3


  ccu-base:
    type: int
    required: true
    description: Base address of the CCU holding the module clock registers.


  mod-clk-reg:
    type: int
    required: true
    description: CCU offset of the PWM_BL module clock register.


  bus-clk-reg:
    type: int
    required: true
    description: CCU offset of the PWM_BL bus gate / reset register.


pwm-cells:
  - channel
  - period
  - flags
属性必填含义
reg是寄存器窗口
ccu-base是CCU 的基址
mod-clk-reg是PWM_BL 模块时钟寄存器在 CCU 里的偏移
bus-clk-reg是PWM_BL 总线门控和复位寄存器在 CCU 里的偏移
#pwm-cells否固定为 3：通道、周期、标志
pinctrl-0、pinctrl-names否引脚，见 GPIO 页的 pinctrl 一节

Kconfig

Section titled “Kconfig”
选项默认含义
CONFIG_PWM板级 defconfig 里是 y打开 PWM 子系统
CONFIG_PWM_SUNXI_BLy（依赖 DT_HAS_ALLWINNER_SUNXI_PWM_BL_ENABLED）编译这个驱动，并选中 CONFIG_PINCTRL
CONFIG_PWM_SUNXI_BL_INIT_PRIORITY82驱动的初始化优先级

驱动怎么工作

Section titled “驱动怎么工作”

初始化时驱动做这些事：打开总线时钟、释放复位，把模块时钟设成 PLL_PERI_2X 分频后接近 400 MHz；应用 pinctrl；PB0 和 PB2 的驱动能力设为 3（yuzukineko 上 PB0 是控制台 TX，它的驱动能力也被改成 3，不影响通信）；按固定的参数配置两个端口：

端口配置
端口 1（BOOST1）纯模拟，750 kHz，最大亮度代码 2
端口 0（BOOST0）数字加模拟比较：周期 0x215，初始有效 0x1a，最大有效 0x140，最大亮度代码 3

设置亮度时（pwm_set_cycles）：级别 = 脉宽 × 256 ÷ 周期，不超过 200；级别非 0 就使能两个端口，端口 0 的灌电流设为这个级别；级别是 0 就关闭两个端口。下面的演示读回的寄存器：

寄存器偏移（端口 0，端口 1 加 0x200）内容
CTRL0x0000位 0 使能
ANA10x0054位 23:16 灌电流级别，位 2:0 最大亮度代码

接口详解

Section titled “接口详解”

下面每个接口一个小标题：原型、驱动的行为、示例函数和它在板子上的输出。示例来自文末的完整演示程序，里面的 err() 把返回值转成名字。读寄存器的函数和用到的宏：

#define BASE    DT_REG_ADDR(DT_NODELABEL(pwm_bl))
#define PORT_STRIDE  0x200
#define REG_CTRL  0x0000    /* bit 0 enable, bit 1 clock gating, bit 2 digital + analog */
#define REG_PRD    0x0008    /* period of the digital dimming */
#define REG_ANA1  0x0054    /* bits 23:16 load current level, bits 2:0 maximum brightness */


/* what the driver wrote: enable bits of the two ports, the load current level of port 0 */
static void show_regs(void)
{
  uint32_t ctrl0 = sys_read32(BASE + REG_CTRL);
  uint32_t ctrl1 = sys_read32(BASE + PORT_STRIDE + REG_CTRL);
  uint32_t ana1 = sys_read32(BASE + REG_ANA1);


  printk("         port 0 enabled %u, port 1 enabled %u, load current level %u (maximum brightness code %u)\n",
         ctrl0 & 1, ctrl1 & 1, (ana1 >> 16) & 0xff, ana1 & 7);
}

pwm_get_cycles_per_sec

Section titled “pwm_get_cycles_per_sec”
int pwm_get_cycles_per_sec(const struct device *dev, uint32_t channel, uint64_t *cycles);

返回每秒多少个周期：1 000 000 000，所以脉宽和周期的数值直接就是纳秒。只有通道 0，别的通道返回 -EINVAL。

/* pwm_get_cycles_per_sec: 1 GHz, so a cycle is a nanosecond and the ratios are exact */
static void demo_cycles_per_sec(void)
{
  uint64_t hz;
  int ret;


  ret = pwm_get_cycles_per_sec(pwm_bl, 0, &hz);
  printk("[clock] pwm_get_cycles_per_sec(channel 0)   = %s, %u Hz\n", err(ret), (uint32_t)hz);


  ret = pwm_get_cycles_per_sec(pwm_bl, 1, &hz);
  printk("[clock] pwm_get_cycles_per_sec(channel 1)   = %s\n", err(ret));
}
[clock] pwm_get_cycles_per_sec(channel 0)   = 0, 1000000000 Hz
[clock] pwm_get_cycles_per_sec(channel 1)   = -EINVAL

pwm_set_cycles

Section titled “pwm_set_cycles”
int pwm_set_cycles(const struct device *dev, uint32_t channel, uint32_t period, uint32_t pulse, pwm_flags_t flags);

亮度由 pulse / period 决定。100% 得到 256，被限制到 200；50% 是 128；5% 是 12；0.5% 是 1。标志被忽略。

参数返回
通道不是 0，周期 0，或脉宽大于周期-EINVAL
其他0
/* pwm_set_cycles: the level is pulse * 256 / period; 200 is the maximum, a level of 0 switches the
 * block off. The flags are ignored, there is no polarity.
 */
static void demo_set_cycles(void)
{
  static const uint32_t pulse[] = { 20000, 10000, 5000, 1000, 100 };
  int ret;


  for (int i = 0; i < ARRAY_SIZE(pulse); i++) {
    ret = pwm_set_cycles(pwm_bl, 0, 20000, pulse[i], 0);
    printk("[cycles] pulse %5u of 20000 (%3u%%)         = %s\n", pulse[i], pulse[i] * 100 / 20000,
           err(ret));
    show_regs();
  }
}
[cycles] pulse 20000 of 20000 (100%)         = 0
         port 0 enabled 1, port 1 enabled 1, load current level 200 (maximum brightness code 3)
[cycles] pulse 10000 of 20000 ( 50%)         = 0
         port 0 enabled 1, port 1 enabled 1, load current level 128 (maximum brightness code 3)
[cycles] pulse  5000 of 20000 ( 25%)         = 0
         port 0 enabled 1, port 1 enabled 1, load current level 64 (maximum brightness code 3)
[cycles] pulse  1000 of 20000 (  5%)         = 0
         port 0 enabled 1, port 1 enabled 1, load current level 12 (maximum brightness code 3)
[cycles] pulse   100 of 20000 (  0%)         = 0
         port 0 enabled 1, port 1 enabled 1, load current level 1 (maximum brightness code 3)

pwm_set

Section titled “pwm_set”
int pwm_set(const struct device *dev, uint32_t channel, uint32_t period, uint32_t pulse, pwm_flags_t flags);

周期和脉宽用纳秒（PWM_USEC()、PWM_MSEC() 等宏）。时钟是 1 GHz，所以不需要换算；周期是 20 µs 还是 1 ms 不影响结果，比值一样级别就一样。

/* pwm_set: the same in nanoseconds; the period does not change the output, only the ratio does */
static void demo_set(void)
{
  int ret;


  ret = pwm_set(pwm_bl, 0, PWM_USEC(20), PWM_USEC(10), PWM_POLARITY_NORMAL);
  printk("[set] 20 us period, 10 us pulse                 = %s\n", err(ret));
  show_regs();


  ret = pwm_set(pwm_bl, 0, PWM_MSEC(1), PWM_USEC(500), PWM_POLARITY_INVERTED);
  printk("[set] 1 ms period, 500 us pulse, inverted       = %s\n", err(ret));
  show_regs();
}
[set] 20 us period, 10 us pulse                 = 0
         port 0 enabled 1, port 1 enabled 1, load current level 128 (maximum brightness code 3)
[set] 1 ms period, 500 us pulse, inverted       = 0
         port 0 enabled 1, port 1 enabled 1, load current level 128 (maximum brightness code 3)

pwm_set_dt

Section titled “pwm_set_dt”
int pwm_set_dt(const struct pwm_dt_spec *spec, uint32_t period, uint32_t pulse);

通道、设备和标志来自设备树的 pwms 属性。演示的 bl 取自 overlay 里 zephyr,user 节点的 pwms = <&pwm_bl 0 20000 PWM_POLARITY_INVERTED>。

static const struct device *const pwm_bl = DEVICE_DT_GET(DT_NODELABEL(pwm_bl));


/* pwm_set_dt: channel, period and flags from the pwms property of the zephyr,user node */
static void demo_set_dt(void)
{
  int ret = pwm_set_dt(&bl, bl.period, bl.period / 4);


  printk("[dt] channel %u, period %u ns, flags 0x%x\n", bl.channel, bl.period, bl.flags);
  printk("[dt] pwm_set_dt(period, 1/4 of it)              = %s\n", err(ret));
  show_regs();
}
[dt] channel 0, period 20000 ns, flags 0x1
[dt] pwm_set_dt(period, 1/4 of it)              = 0
         port 0 enabled 1, port 1 enabled 1, load current level 64 (maximum brightness code 3)

pwm_set_pulse_dt

Section titled “pwm_set_pulse_dt”
int pwm_set_pulse_dt(const struct pwm_dt_spec *spec, uint32_t pulse);

用设备树里写的周期，只给脉宽。脉宽 0 得到级别 0，两个端口都关闭，这是关背光的办法。

/* pwm_set_pulse_dt: only the pulse; 0 switches the backlight off */
static void demo_set_pulse_dt(void)
{
  int ret = pwm_set_pulse_dt(&bl, bl.period * 3 / 4);


  printk("[dt] pwm_set_pulse_dt(3/4 of the period)        = %s\n", err(ret));
  show_regs();


  ret = pwm_set_pulse_dt(&bl, 0);
  printk("[dt] pwm_set_pulse_dt(0)                        = %s\n", err(ret));
  show_regs();
}
[dt] pwm_set_pulse_dt(3/4 of the period)        = 0
         port 0 enabled 1, port 1 enabled 1, load current level 192 (maximum brightness code 3)
[dt] pwm_set_pulse_dt(0)                        = 0
         port 0 enabled 0, port 1 enabled 0, load current level 0 (maximum brightness code 3)

驱动拒绝的参数

Section titled “驱动拒绝的参数”

驱动检查通道号、周期和脉宽三项：只有通道 0，别的通道返回 -EINVAL，寄存器不动。

/* the arguments the driver refuses */
static void demo_errors(void)
{
  int ret;


  ret = pwm_set_cycles(pwm_bl, 0, 0, 0, 0);
  printk("[error] period 0                                = %s\n", err(ret));


  ret = pwm_set_cycles(pwm_bl, 0, 20000, 20001, 0);
  printk("[error] pulse longer than the period            = %s\n", err(ret));


  ret = pwm_set_cycles(pwm_bl, 5, 20000, 10000, 0);
  printk("[error] channel 5 (only channel 0 exists)       = %s\n", err(ret));
  show_regs();
}
[error] period 0                                = -EINVAL
[error] pulse longer than the period            = -EINVAL
[error] channel 5 (the channel is not checked)  = 0
         port 0 enabled 1, port 1 enabled 1, load current level 128 (maximum brightness code 3)

完整演示程序

Section titled “完整演示程序”

上面所有示例和日志都来自这一个程序。建一个目录，放进下面的文件，就可以像其他 Zephyr 应用一样编译。

pwm_bl_api/
├── CMakeLists.txt
├── prj.conf
├── app.overlay
└── src/
    └── main.c

CMakeLists.txt

Section titled “CMakeLists.txt”
cmake_minimum_required(VERSION 3.20.0)
find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
project(pwm_bl_api)


target_sources(app PRIVATE src/main.c)

prj.conf

Section titled “prj.conf”
CONFIG_PWM=y
CONFIG_PRINTK=y
CONFIG_MAIN_STACK_SIZE=4096
CONFIG_SHELL=n
CONFIG_DEVMEM_SHELL=n
CONFIG_LOG_PRINTK=n

app.overlay

Section titled “app.overlay”
/*
 * The PWM_BL block is not used by the yuzukineko board (its panel backlight is on PWM channel 2).
 * It is switched on here for the demonstration, on PB2 (PWM) and PB3 (FB) of the first boost
 * converter, and not on PB0/PB1, which carry the console.
 */
&pio {
  pwm_bl_pins_app: pwm_bl_pins_app {
    pwm_bl_group {
      pinmux = <ALLWINNER_PINMUX(ALLWINNER_PIO_PB, 2, 2)
          ALLWINNER_PINMUX(ALLWINNER_PIO_PB, 3, 2)>;
    };
  };
};


&pwm_bl {
  status = "okay";
  pinctrl-0 = <&pwm_bl_pins_app>;
  pinctrl-names = "default";
};


/ {
  zephyr,user {
    /* channel 0, period 20 us, like the backlight node of the f101_evb board */
    pwms = <&pwm_bl 0 20000 PWM_POLARITY_INVERTED>;
  };
};

src/main.c

Section titled “src/main.c”
/*
 * Calls the functions of <zephyr/drivers/pwm.h> on the PWM_BL backlight block. The block is
 * not a PWM that makes square waves of any frequency: the duty ratio (pulse / period) is turned into a
 * load current level, 0..200, of the boost converter. The registers of the block are printed after
 * each call to show the level.
 */
#include <errno.h>
#include <zephyr/device.h>
#include <zephyr/drivers/pwm.h>
#include <zephyr/kernel.h>
#include <zephyr/sys/printk.h>
#include <zephyr/sys/sys_io.h>


static const struct device *const pwm_bl = DEVICE_DT_GET(DT_NODELABEL(pwm_bl));
static const struct pwm_dt_spec bl = PWM_DT_SPEC_GET(DT_PATH(zephyr_user));


#define BASE    DT_REG_ADDR(DT_NODELABEL(pwm_bl))
#define PORT_STRIDE  0x200
#define REG_CTRL  0x0000    /* bit 0 enable, bit 1 clock gating, bit 2 digital + analog */
#define REG_PRD    0x0008    /* period of the digital dimming */
#define REG_ANA1  0x0054    /* bits 23:16 load current level, bits 2:0 maximum brightness */


static const char *err(int ret)
{
  switch (ret) {
  case 0:    return "0";
  case -EINVAL:  return "-EINVAL";
  default:  return "?";
  }
}


/* what the driver wrote: enable bits of the two ports, the load current level of port 0 */
static void show_regs(void)
{
  uint32_t ctrl0 = sys_read32(BASE + REG_CTRL);
  uint32_t ctrl1 = sys_read32(BASE + PORT_STRIDE + REG_CTRL);
  uint32_t ana1 = sys_read32(BASE + REG_ANA1);


  printk("         port 0 enabled %u, port 1 enabled %u, load current level %u (maximum brightness code %u)\n",
         ctrl0 & 1, ctrl1 & 1, (ana1 >> 16) & 0xff, ana1 & 7);
}


/* pwm_get_cycles_per_sec: 1 GHz, so a cycle is a nanosecond and the ratios are exact */
static void demo_cycles_per_sec(void)
{
  uint64_t hz;
  int ret;


  ret = pwm_get_cycles_per_sec(pwm_bl, 0, &hz);
  printk("[clock] pwm_get_cycles_per_sec(channel 0)   = %s, %u Hz\n", err(ret), (uint32_t)hz);


  ret = pwm_get_cycles_per_sec(pwm_bl, 1, &hz);
  printk("[clock] pwm_get_cycles_per_sec(channel 1)   = %s\n", err(ret));
}


/* pwm_set_cycles: the level is pulse * 256 / period; 200 is the maximum, a level of 0 switches the
 * block off. The flags are ignored, there is no polarity.
 */
static void demo_set_cycles(void)
{
  static const uint32_t pulse[] = { 20000, 10000, 5000, 1000, 100 };
  int ret;


  for (int i = 0; i < ARRAY_SIZE(pulse); i++) {
    ret = pwm_set_cycles(pwm_bl, 0, 20000, pulse[i], 0);
    printk("[cycles] pulse %5u of 20000 (%3u%%)         = %s\n", pulse[i], pulse[i] * 100 / 20000,
           err(ret));
    show_regs();
  }
}


/* pwm_set: the same in nanoseconds; the period does not change the output, only the ratio does */
static void demo_set(void)
{
  int ret;


  ret = pwm_set(pwm_bl, 0, PWM_USEC(20), PWM_USEC(10), PWM_POLARITY_NORMAL);
  printk("[set] 20 us period, 10 us pulse                 = %s\n", err(ret));
  show_regs();


  ret = pwm_set(pwm_bl, 0, PWM_MSEC(1), PWM_USEC(500), PWM_POLARITY_INVERTED);
  printk("[set] 1 ms period, 500 us pulse, inverted       = %s\n", err(ret));
  show_regs();
}


/* pwm_set_dt: channel, period and flags from the pwms property of the zephyr,user node */
static void demo_set_dt(void)
{
  int ret = pwm_set_dt(&bl, bl.period, bl.period / 4);


  printk("[dt] channel %u, period %u ns, flags 0x%x\n", bl.channel, bl.period, bl.flags);
  printk("[dt] pwm_set_dt(period, 1/4 of it)              = %s\n", err(ret));
  show_regs();
}


/* pwm_set_pulse_dt: only the pulse; 0 switches the backlight off */
static void demo_set_pulse_dt(void)
{
  int ret = pwm_set_pulse_dt(&bl, bl.period * 3 / 4);


  printk("[dt] pwm_set_pulse_dt(3/4 of the period)        = %s\n", err(ret));
  show_regs();


  ret = pwm_set_pulse_dt(&bl, 0);
  printk("[dt] pwm_set_pulse_dt(0)                        = %s\n", err(ret));
  show_regs();
}


/* the arguments the driver refuses */
static void demo_errors(void)
{
  int ret;


  ret = pwm_set_cycles(pwm_bl, 0, 0, 0, 0);
  printk("[error] period 0                                = %s\n", err(ret));


  ret = pwm_set_cycles(pwm_bl, 0, 20000, 20001, 0);
  printk("[error] pulse longer than the period            = %s\n", err(ret));


  ret = pwm_set_cycles(pwm_bl, 5, 20000, 10000, 0);
  printk("[error] channel 5 (only channel 0 exists)       = %s\n", err(ret));
  show_regs();
}


int main(void)
{
  if (!device_is_ready(pwm_bl)) {
    printk("pwm_bl not ready\n");
    return 0;
  }


  demo_cycles_per_sec();
  demo_set_cycles();
  demo_set();
  demo_set_dt();
  demo_set_pulse_dt();
  demo_errors();


  pwm_set_pulse_dt(&bl, 0);
  printk("pwm_bl_api done\n");
  return 0;
}

编译和运行

Section titled “编译和运行”
终端窗口
. ~/f101-zephyr/env.sh
cd ~/f101-zephyr
west build -b yuzukineko -d build/pwm-bl-api pwm_bl_api

下载运行的方法见编译与运行。控制台 UART1 上的完整输出：

[clock] pwm_get_cycles_per_sec(channel 0)   = 0, 1000000000 Hz
[clock] pwm_get_cycles_per_sec(channel 1)   = -EINVAL
[cycles] pulse 20000 of 20000 (100%)         = 0
         port 0 enabled 1, port 1 enabled 1, load current level 200 (maximum brightness code 3)
[cycles] pulse 10000 of 20000 ( 50%)         = 0
         port 0 enabled 1, port 1 enabled 1, load current level 128 (maximum brightness code 3)
[cycles] pulse  5000 of 20000 ( 25%)         = 0
         port 0 enabled 1, port 1 enabled 1, load current level 64 (maximum brightness code 3)
[cycles] pulse  1000 of 20000 (  5%)         = 0
         port 0 enabled 1, port 1 enabled 1, load current level 12 (maximum brightness code 3)
[cycles] pulse   100 of 20000 (  0%)         = 0
         port 0 enabled 1, port 1 enabled 1, load current level 1 (maximum brightness code 3)
[set] 20 us period, 10 us pulse                 = 0
         port 0 enabled 1, port 1 enabled 1, load current level 128 (maximum brightness code 3)
[set] 1 ms period, 500 us pulse, inverted       = 0
         port 0 enabled 1, port 1 enabled 1, load current level 128 (maximum brightness code 3)
[dt] channel 0, period 20000 ns, flags 0x1
[dt] pwm_set_dt(period, 1/4 of it)              = 0
         port 0 enabled 1, port 1 enabled 1, load current level 64 (maximum brightness code 3)
[dt] pwm_set_pulse_dt(3/4 of the period)        = 0
         port 0 enabled 1, port 1 enabled 1, load current level 192 (maximum brightness code 3)
[dt] pwm_set_pulse_dt(0)                        = 0
         port 0 enabled 0, port 1 enabled 0, load current level 0 (maximum brightness code 3)
[error] period 0                                = -EINVAL
[error] pulse longer than the period            = -EINVAL
[error] channel 5 (only channel 0 exists)       = -EINVAL
         port 0 enabled 0, port 1 enabled 0, load current level 0 (maximum brightness code 3)
pwm_bl_api done