DALI通信的原理及实现方法-电子发烧友网

在双碳目标下，具有调光功能的LED驱动电源是重要的分支。 DALI通信常用在LED的数字调光控制中，下文将通过C语言与单片机结合，解释DALI的原理及实现方法。

一、通信原理

1.1 DALI 的物理电平信号定义如下：

9.5~22.5V：高电平或者DALI 空闲状态

6.5~9.5V：未定义

-6.5V~6.5V：定义为低电平

1.2 波特率：1200bps + 10%

1.3 DALI 负载最大短路电流<250mA

当从机发生故障，例如短路时，DALI总线上的电流，需要限制在250mA以下。

1.4 编码方式

使用曼切斯特编码，即上升沿为信号1，下降沿为信号0。

1.5 主机发送指令结构

主机发送的包含1个起始位、1个地址位类型位、6个地址位、一个选择位、8个数据位和两个停止位。

1.6 从机回复指令结构

从机向主机回复包含1个起始位、8个数据位和两个停止位。

1.7 前向帧与后向帧时序约束

Te表示半个位的时间，即4.16.67uS;

两个前向帧时间间隔大于22个Te;

前向帧与后向帧之间时间间隔为7~22个Te;

后向帧与前向帧之间时间间隔大于22个Te;

1.8 主机与从机的握手

主机在发送指令后，在等候响应阶段，

如果收到从机发送的”0xFF“，就会认为从机接收成功;

如果在这个阶段处于空闲状态，就会认为从机没有接收成功;

二、实现方法

2.1 硬件原理图

下面的硬件主要是将DALI的电平信号，转为单片机能够接受的电平，下面那张是微芯公司DALI的参考通信电路。

2.1 从机接收思路及实现

本次从机的接收端，主要使用了一个边沿检测中断和一个定时器中断。

代码思路：

1)由于空闲状态，接收端的电平为高电平，产生起始信号时，需要从产生一个上升沿。于是，使用了外部下降沿触发中断，并关闭边沿触发中断;

2)检测到第一个下降沿后，定时器定时到0.75个周期，0.75个周期后读取第一位数据，并修改定时器周期为1个数据位时长。

3)第二次定时结束时读取第二位数据，依次读取后面的数据

4)当读到最后一位数据的时候，也就是LSB后的两位时，停止定时器，并初始化定时器为0.75个数据周期，然后开启边沿触发中断。

C语言程序：

1 //配置边沿触发及中断
  2 void IO_Change_Init(void){  
  3     
  4     //Set the CN2 as the IO state change flag 
  5     CNEN1bits.CN2IE=1;//Open the IO state interrupt
  6     CNPU1bits.CN2PUE=0;//Disable the weak up
  7     
  8     IFS1bits.CNIF=0;//Clear the interrupt flag
  9     IPC4bits.CNIP=7;//Configure the interrupt level 7
 10     IEC1bits.CNIE=1;//Enable this interrupt
 11 }
 12 //检测到第一个下降沿
 13 void __attribute__ ((__interrupt__,__no_auto_psv__)) _CNInterrupt(void){
 14    
 15    IFS1bits.CNIF = 0; //Clear the interrupt flag 
 16    
 17    //Disable the IO State Interrupt and start the Time
 18    T1CONbits.TON = 1;
 19    CNEN1bits.CN2IE = 0;
 20    
 21 }
 22 //配置定时器初使周期为0.75个数据位时长
 23 void Tim1_Init(void){
 24     T1CON = 0x0020;
 25     
 26     IEC0bits.T1IE = 1;
 27     IPC0bits.T1IP = 7;
 28     IFS0bits.T1IF = 0;
 29     
 30     TMR1 = 0;
 31     PR1 = 390;
 32     T1CONbits.TON = 0;
 33 }
 34 //在定时器中断里面读取数据
 35 void __attribute__((__interrupt__,auto_psv,__shadow__)) _T1Interrupt(void)
 36 {
 37     IFS0bits.T1IF = 0;
 38 
 39     if(LLC_DALI_Rx_Mode == 1)
 40     {
 41         switch(Timer_Num)
 42         {
 43             case 0:
 44                 Timer_Num++;
 45                 T1CONbits.TON = 0; //关闭定时器
 46                 PR1 = 520; //设置下一个定时时长为1个周期
 47                 TMR1 = 0;//初使化定时器初始值
 48                 T1CONbits.TON = 1;//开启定时器
 49                 break;
 50             case 1:
 51                 if(_RB0 == 1 )Address_temp |= (1<<7);
 52                 Timer_Num++;
 53                 break;
 54             case 2:
 55                 if(_RB0 == 1 )Address_temp |= (1<<6);
 56                 Timer_Num++;
 57                 break;
 58             case 3:
 59                 if(_RB0 == 1 )Address_temp |= (1<<5);
 60                 Timer_Num++;            
 61                 break;
 62             case 4:
 63                 if(_RB0 == 1 )Address_temp |= (1<<4);
 64                 Timer_Num++;
 65                 break;
 66             case 5:
 67                 if(_RB0 == 1 )Address_temp |= (1<<3);
 68                 Timer_Num++;            
 69                 break;
 70             case 6:
 71                 if(_RB0 == 1 )Address_temp |= (1<<2);
 72                 Timer_Num++;        
 73                 break;
 74             case 7:
 75                 if(_RB0 == 1 )Address_temp |= (1<<1);
 76                 Timer_Num++;
 77                 break;
 78             case 8:
 79                 if(_RB0 == 1 )Address_temp |= (1<<0);
 80                 Timer_Num++;
 81                 break;
 82             case 9:
 83                 if(_RB0 == 1 )Command_temp |= (1<<7);
 84                 Timer_Num++;
 85                 break;
 86             case 10:
 87                 if(_RB0 == 1 )Command_temp |= (1<<6);
 88                 Timer_Num++;
 89                 break;
 90             case 11:
 91                 if(_RB0 == 1 )Command_temp |= (1<<5);
 92                 Timer_Num++;
 93                 break;
 94             case 12:
 95                 if(_RB0 == 1 )Command_temp |= (1<<4);
 96                 Timer_Num++;
 97                 break;
 98             case 13:
 99                 if(_RB0 == 1 )Command_temp |= (1<<3);
100                 Timer_Num++;
101                 break;
102             case 14:
103                 if(_RB0 == 1 )Command_temp |= (1<<2);
104                 Timer_Num++;
105                 break;
106             case 15:
107                 if(_RB0 == 1 )Command_temp |= (1<<1);
108                 Timer_Num++;
109                 break;
110             case 16:
111                 if(_RB0 == 1 )Command_temp |= (1<<0);
112                 Timer_Num++;
113                 break;
114             case 17:
115                 if(_RB0 == 1 )StopBit_temp |= (1<<1);
116                 Timer_Num++;
117                 break;
118             case 18:
119                 if(_RB0 == 1 )StopBit_temp |= (1<<0);
120                 Timer_Num++;
121                 break;
122             case 19:
123                    T1CONbits.TON = 0;//关闭定时器
124                    PR1 = 390;//设置下一个定时器周期为0.75个数据位时长
125                    TMR1 = 0;//定时器计数初始值置0
126                    CNEN1bits.CN2IE = 1;//开启边沿检测中断
127                    //数据获取，这里还可以添加数据包检验程序
128                    Command = Command_temp;
129                    Address = Address_temp;
130                    StopBit = StopBit_temp;
131 
132                    Command_temp = 0;
133                    Address_temp = 0;
134                    StopBit_temp = 0;
135                    Timer_Num = 0;
136                 break;
137         }
138     }
139     
140 
141

2.2 从机思路及实现

从机的回复相对较简单，只需要在每半个数据位修改输出引脚的电平。分别发送1个起始位、8个数据位和两个停止位。

代码思路：

1)接收数据完成并定时等待8Te

2)发送一个引脚低电平，并设置下一个定时周期为Te，定时器初使值为0，并开启定时器;

3)在后面的定时器中断里面，发送起始位;

4)在后面的定时器中断里面，发送数据位;

5)在后面的定时器中断里面，发送停止位;

6)初使化发送数据计数变量，初始化定时器计数值为零，关闭定时器;

7)开启边沿触发中断;

C语言程序实现

1   if(LLC_DALI_Tx_Mode == 1){
 2         switch(Timer_Num)
 3         {
 4             case 0:
 5                 //Send the Start Bit
 6                 _RF3 = 0;
 7                 T1CONbits.TON = 0;
 8                 PR1 = 260;
 9                 TMR1 = 0;
10                 T1CONbits.TON = 1;
11                 Timer_Num++;
12                 break;
13             case 1:
14                 _RF3 = 1;
15                 Timer_Num++;
16                 break;
17             case 2:
18                  //Send the Data Bits
19                 _RF3 = ((Transfer_Data & 0x80)>0)?0:1;
20                 Timer_Num++;
21                 break;
22             case 3:
23                 _RF3 = ((Transfer_Data & 0x80)>0)?1:0;
24                 Timer_Num++;            
25                 break;
26             case 4:
27                  _RF3 = ((Transfer_Data & 0x40)>0)?0:1;
28                 Timer_Num++;
29                 break;
30             case 5:
31                 _RF3 = ((Transfer_Data & 0x40)>0)?1:0;
32                 Timer_Num++;            
33                 break;
34             case 6:
35                 _RF3 = ((Transfer_Data & 0x20)>0)?0:1;
36                 Timer_Num++;        
37                 break;
38             case 7:
39                 _RF3 = ((Transfer_Data & 0x20)>0)?1:0;
40                 Timer_Num++;
41                 break;
42             case 8:
43                 _RF3 = ((Transfer_Data & 0x10)>0)?0:1;
44                 Timer_Num++;
45                 break;
46             case 9:
47                 _RF3 = ((Transfer_Data & 0x10)>0)?1:0;
48                 Timer_Num++;
49                 break;
50             case 10:
51                 _RF3 = ((Transfer_Data & 0x08)>0)?0:1;
52                 Timer_Num++;
53                 break;
54             case 11:
55                 _RF3 = ((Transfer_Data & 0x08)>0)?1:0;
56                 Timer_Num++;
57                 break;
58             case 12:
59                 _RF3 = ((Transfer_Data & 0x04)>0)?0:1;
60                 Timer_Num++;
61                 break;
62             case 13:
63                 _RF3 = ((Transfer_Data & 0x04)>0)?1:0;
64                 Timer_Num++;
65                 break;
66             case 14:
67                 _RF3 = ((Transfer_Data & 0x02)>0)?0:1;
68                 Timer_Num++;
69                 break;
70             case 15:
71                 _RF3 = ((Transfer_Data & 0x02)>0)?1:0;
72                 Timer_Num++;
73                 break;
74             case 16:
75                 _RF3 = ((Transfer_Data & 0x01)>0)?0:1;
76                 Timer_Num++;
77                 break;
78             case 17:
79                 _RF3 = ((Transfer_Data & 0x01)>0)?1:0;
80                 Timer_Num++;
81                 break;
82             case 18:
83                 //Send the stop bit;
84                 T1CONbits.TON = 0;
85                 TMR1 = 0;
86                 PR1 = 260<<2;
87                 T1CONbits.TON = 1;
88                 _RF3 = 1;
89                 Timer_Num++;
90                 break;
91             case 19:
92                    T1CONbits.TON = 0;  //关闭定时器
93                    CNEN1bits.CN2IE = 1;//开启边沿检测中断
94                    TMR1 = 0;  //定时器初始值置0
95                    PR1 = 260; //定时器周期设置为Te
96                    Timer_Num = 0;//初使定时器数据位计数
97                 break;
98         }
99     }