在 Avaota SBC 的开发板中，通常会有几个 WS2812 RGB LED 灯。例如 Avaota A1 的如下位置：
对于 AvaotaOS，提供了硬件的 LEDC（Light Emitting Diode Controller），发光二极管控制器作为WS2812 RGB LED 灯的控制器。每个 LED 的三基色均可实现 256 级亮度显示，因此整个 LED 可完成 256ˆ3（即 16777216）种颜色的全真色彩显示。模块支持最大1024颗外控 LED级联。
WS2812 驱动介绍
LED 典型电路如图所示，其中 DI 表示控制数据输入脚，DO 表示控制数据输出脚。DI 端接收从控制器传过来的数据，每个 LED 内部的数据锁存器会存储 24bit 数据，剩余的数据经过内部整形处理电路整形放大后通过 DO 端口开始转发输出给下一个级联的 LED。因此，每经过一个LED，数据减少 24bit。
LED典型电路如上图所示，其中 DI 表示控制数据输入脚，DO 表示控制数据输出脚。DI 端接受从控制器传输过来的数据，每个 LED 内部的数据锁存器会存储 24bit (分别对应 R,G,B 三种颜色)数据，剩余的数据经过内部整形处理电路整形放大后通过 DO 端口开始转发输出给下一个级联的 LED 。因此，每经过一个 LED ，数据减少 24bit。
WS2812 驱动配置说明
配置驱动，默认 Avaota OS 已经勾选该驱动。如果未勾选请配置
LED Drivers ->
<*> LEDC Support for Allwinner SoCs
配置设备树，首先需要配置 PIO 节点，配置 LEDC 使用的 GPIO
&pio {
ledc_pins_a: ledc@0{
pins ="PH19";
function ="ledc";
drive-strength =<10>;
};
ledc_pins_b: ledc@1{
pins ="PH19";
function ="gpio_in";
};
};
然后配置 LEDC 模块的数值
&ledc {
pinctrl-names ="default","sleep";
pinctrl-0=<&ledc_pins_a>;
pinctrl-1=<&ledc_pins_b>;
led_count =<4>;
output_mode ="GRB";
reset_ns =<84>;
t1h_ns =<800>;
t1l_ns =<320>;
t0h_ns =<300>;
t0l_ns =<800>;
wait_time0_ns =<84>;
wait_time1_ns =<84>;
wait_data_time_ns =<600000>;
status ="okay";
};
pinctrl-names: 用于表示 0 和 1 的 pinctrl 哪个是默认和休眠状态。pinctrl-0: 引脚配置，这里是默认使用的时候配置。pinctrl-1: 同上，这里是休眠时的配置。led_count: LED 灯的数目，根据硬件配置。output_mode: LED 灯输出模式，根据 LED 灯的 datasheet 进行配置。reset_ns: LED 灯 reset 时间控制。t1h_ns: 1 码高电平时间，根据 LED 灯的 datasheet 进行配置。t1l_ns: 1 码低电平时间，根据 LED 灯的 datasheet 进行配置。t0h_ns: 0 码高电平时间，根据 LED 灯的 datasheet 进行配置。t0l_ns: 0 码低电平时间，根据 LED 灯的 datasheet 进行配置。wait_time0_ns: 两个 LED 数据之间的等待时间，根据 LED 灯的 datasheet 进行配置。wait_time1_ns: 帧数据之间的等待时间，根据 LED 灯的 datasheet 进行配置。wait_data_time_ns: 内部 FIFO 等待数据时间，超过时间触发异常中断。status: 设备状态。
WS2812 使用说明
驱动会在 /sys/class/leds 注册每个LED对应的设备目录
/sys/class/leds/sunxi_led0r // 红色
/sys/class/leds/sunxi_led0g // 绿色
/sys/class/leds/sunxi_led0b // 蓝色
其中 0 表示LED的编号，如果是 1 号 LED 则是
/sys/class/leds/sunxi_led1r
/sys/class/leds/sunxi_led1g
/sys/class/leds/sunxi_led1b
需要调节第 0 个LED的颜色为白光且最亮，操作如下：
echo 255 > /sys/class/leds/sunxi_led0r/brightness
echo 255 > /sys/class/leds/sunxi_led0g/brightness
echo 255 > /sys/class/leds/sunxi_led0b/brightness
实现七彩流水灯
C 语言实现
#include<fcntl.h>
#include<stdint.h>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<sys/times.h>
#include<sys/types.h>
#include<unistd.h>
// 使用RGB 分量合成颜色值
#defineMERAGECOLOR(G, R, B)(((uint32_t)G <<16)|((uint16_t)R <<8)| B)
#definePIXEL_NUM4
int fd[PIXEL_NUM][3];// 存放文件描述符数组
voidinit_leds(){
char path[100];
// 初始化LED文件描述符
for(int i =0; i < PIXEL_NUM;++i){
snprintf(path,sizeof(path),"/sys/class/leds/sunxi_led%d%c/brightness", i,'r');
fd[i][0]=open(path, O_WRONLY);
if(fd[i][0]==-1){
printf("Failed to open file for LED %d, color %c\n", i,'r');
}
snprintf(path,sizeof(path),"/sys/class/leds/sunxi_led%d%c/brightness", i,'g');
fd[i][1]=open(path, O_WRONLY);
if(fd[i][1]==-1){
printf("Failed to open file for LED %d, color %c\n", i,'g');
}
snprintf(path,sizeof(path),"/sys/class/leds/sunxi_led%d%c/brightness", i,'b');
fd[i][2]=open(path, O_WRONLY);
if(fd[i][2]==-1){
printf("Failed to open file for LED %d, color %c\n", i,'b');
}
}
}
voidsunxi_set_led_brightness(int led_id,uint8_t r,uint8_t g,uint8_t b){
if(led_id <0|| led_id >= PIXEL_NUM){
printf("Invalid LED ID\n");
return;
}
dprintf(fd[led_id][0],"%d", r);
dprintf(fd[led_id][1],"%d", g);
dprintf(fd[led_id][2],"%d", b);
}
voidclose_leds(){
// 关闭LED文件描述符
for(int i =0; i < PIXEL_NUM;++i){
for(int j =0; j <3;++j){
if(fd[i][j]!=-1){
close(fd[i][j]);
}
}
}
}
// 生成颜色
uint32_tWS281x_Wheel(uint8_t wheelPos){
wheelPos =255- wheelPos;
if(wheelPos <85){
returnMERAGECOLOR(255- wheelPos *3,0, wheelPos *3);
}
if(wheelPos <170){
wheelPos -=85;
returnMERAGECOLOR(0, wheelPos *3,255- wheelPos *3);
}
wheelPos -=170;
returnMERAGECOLOR(wheelPos *3,255- wheelPos *3,0);
}
// 亮度设置
voidWS281xLSet(uint32_t id,uint32_t rgb,float k){
uint8_t r, g, b;
float h, s, v;
uint8_t cmax, cmin, cdes;
r =(uint8_t)(rgb >>16);
g =(uint8_t)(rgb >>8);
b =(uint8_t)(rgb);
cmax = r > g ? r : g;
if(b > cmax)
cmax = b;
cmin = r < g ? r : g;
if(b < cmin)
cmin = b;
cdes = cmax - cmin;
v = cmax /255.0f;
s = cmax ==0?0: cdes /(float) cmax;
h =0;
if(cmax == r && g >= b)
h =((g - b)*60.0f/ cdes)+0;
elseif(cmax == r && g < b)
h =((g - b)*60.0f/ cdes)+360;
elseif(cmax == g)
h =((b - r)*60.0f/ cdes)+120;
else
h =((r - g)*60.0f/ cdes)+240;
v *= k;
float f, p, q, t;
float rf, gf, bf;
int i =((int)(h /60)%6);
f =(h /60)- i;
p = v *(1- s);
q = v *(1- f * s);
t = v *(1-(1- f)* s);
switch(i){
case0:
rf = v;
gf = t;
bf = p;
break;
case1:
rf = q;
gf = v;
bf = p;
break;
case2:
rf = p;
gf = v;
bf = t;
break;
case3:
rf = p;
gf = q;
bf = v;
break;
case4:
rf = t;
gf = p;
bf = v;
break;
case5:
rf = v;
gf = p;
bf = q;
break;
default:
break;
}
r =(uint8_t)(rf *255.0);
g =(uint8_t)(gf *255.0);
b =(uint8_t)(bf *255.0);
sunxi_set_led_brightness(id, r, g, b);
}
// 测试 LEDC
intmain(){
int i =0, j =0, err;
int mode =0;
uint8_t R =0, G =0, B =0;
init_leds();
while(1){
for(j =0; j <256; j++){
for(i =0; i < PIXEL_NUM; i++){
WS281xLSet(i,WS281x_Wheel(((i *256/ PIXEL_NUM)+ j)&255),0.1);
}
usleep(1000);
}
usleep(10000);
}
close_leds();
return1;
}
Python 实现
import os
import time
import math
PIXEL_NUM =4
fd =[[None,None,None]for _ inrange(PIXEL_NUM)]# 文件描述符数组
definit_leds():
global fd
path =""
# 初始化LED文件描述符
for i inrange(PIXEL_NUM):
path =f"/sys/class/leds/sunxi_led{i}{'r'}/brightness"
fd[i][0]= os.open(path, os.O_WRONLY)
if fd[i][0]==-1:
print(f"Failed to open file for LED {i}, color {'r'}")
path =f"/sys/class/leds/sunxi_led{i}{'g'}/brightness"
fd[i][1]= os.open(path, os.O_WRONLY)
if fd[i][1]==-1:
print(f"Failed to open file for LED {i}, color {'g'}")
path =f"/sys/class/leds/sunxi_led{i}{'b'}/brightness"
fd[i][2]= os.open(path, os.O_WRONLY)
if fd[i][2]==-1:
print(f"Failed to open file for LED {i}, color {'b'}")
defsunxi_set_led_brightness(led_id, r, g, b):
if led_id <0or led_id >= PIXEL_NUM:
print("Invalid LED ID")
return
os.write(fd[led_id][0],str(r).encode())
os.write(fd[led_id][1],str(g).encode())
os.write(fd[led_id][2],str(b).encode())
defclose_leds():
# 关闭LED文件描述符
global fd
for i inrange(PIXEL_NUM):
for j inrange(3):
if fd[i][j]isnotNone:
os.close(fd[i][j])
defws281x_wheel(wheel_pos):
wheel_pos =255- wheel_pos
if wheel_pos <85:
return merge_color(255- wheel_pos *3,0, wheel_pos *3)
if wheel_pos <170:
wheel_pos -=85
return merge_color(0, wheel_pos *3,255- wheel_pos *3)
wheel_pos -=170
return merge_color(wheel_pos *3,255- wheel_pos *3,0)
defmerge_color(r, g, b):
return(r <<16)|(g <<8)| b
defws281x_lset(id, rgb, k):
r =(rgb >>16)&0xFF
g =(rgb >>8)&0xFF
b = rgb &0xFF
cmax =max(r, g, b)
cmin =min(r, g, b)
cdes = cmax - cmin
v = cmax /255.0
s = cmax /255.0if cmax ==0else cdes / cmax
if cmax == r and g >= b:
h =(g - b)*60.0/ cdes +0
elif cmax == r and g < b:
h =(g - b)*60.0/ cdes +360
elif cmax == g:
h =(b - r)*60.0/ cdes +120
else:
h =(r - g)*60.0/ cdes +240
v *= k
i = math.floor(h /60)%6
f = h /60- i
p = v *(1- s)
q = v *(1- f * s)
t = v *(1-(1- f)* s)
if i ==0:
rf, gf, bf = v, t, p
elif i ==1:
rf, gf, bf = q, v, p
elif i ==2:
rf, gf, bf = p, v, t
elif i ==3:
rf, gf, bf = p, q, v
elif i ==4:
rf, gf, bf = t, p, v
else:
rf, gf, bf = v, p, q
r =int(rf *255.0)
g =int(gf *255.0)
b =int(bf *255.0)
sunxi_set_led_brightness(id, r, g, b)
defmain():
init_leds()
try:
whileTrue:
for j inrange(256):
for i inrange(PIXEL_NUM):
ws281x_lset(i, ws281x_wheel(int((float(i)*256.0/float(PIXEL_NUM)+ j))&255),0.1)
time.sleep(0.01)# 控制LED变化速度
time.sleep(0.1)
finally:
close_leds()
if __name__ =="__main__":
main()
