ARM9 在AD驱动程序中的问题

dhd1111 2012-10-16 08:15:18

1. #define GLOBAL_CLK 1
2. #include <stdlib.h>
3. #include <string.h>
4. #include "def.h"
5. #include "option.h"
6. #include "2440addr.h"
7. #include "2440lib.h"
8. #include "2440slib.h"
9. #include "mmu.h"
10. #include "profile.h"
11. #include "memtest.h"
12.
13.
14. #define ADC_FREQ 2500000
15. //#define ADC_FREQ 1250000
16.
17.
18. volatile U32 preScaler;
19.
20. void adc_init(void);
21. int ReadAdc(int channel);
22. static void cal_cpu_bus_clk(void);
23. void Set_Clk(void);
24. void beep_init(void);
25. void beep_run(void);
26. /*************************************************
27. Function name: delay
28. Parameter : times
29. Description : 延时函数
30. Return : void
31. Argument : void
32. Autor & date : Daniel
33. **************************************************/
34. void delay(int times)
35. {
36. int i,j;
37. for(i=0;i<times;i++)
38. for(j=0;j<400;j++);
39. }
40. /*************************************************
41. Function name: Main
42. Parameter : void
43. Description : 主功能函数
44. Return : void
45. Argument : void
46. Autor & date : Daniel
47. **************************************************/
48. void Main(void)
49. {
50. int a0=0,tmp;
51. int Scom=0;
52. Set_Clk();
53. Uart_Init(0,115200);
54. Uart_Select(Scom);
55.
56. adc_init();
57. while(1)
58. {
59. a0=ReadAdc(0);
60. Uart_Printf( "AIN0: %04d\n", a0);
61. delay(1000) ;
62. }
63.
64. }
65.
66. /*************************************************
67. Function name: adc_init()
68. Parameter : int channel
69. Description : adc初始化
70. Return : void
71. Argument : void
72. Autor & date : Daniel
73. **************************************************/
74. void adc_init(void)
75. {
76. int channel=0; //AIN0，对应开发板上W1可调电阻
77.
78. preScaler = ADC_FREQ;
79. Uart_Printf("ADC conv,freq. = %dHz\n",preScaler);
80. preScaler = 50000000/ADC_FREQ - 1; //PCLK=50M 我们要得到ADC_FREQ=2500000
81.
82. Uart_Printf("PRSCVL=PCLK/ADC_FREQ - 1=%d\n",preScaler);
83.
84. /*AD转换频率设置，最大频率为2.5MHz*/
85. rADCCON = (1<<14)|(preScaler<<6)|(channel<<3); //setup channel 1<<14使能预分频器 (preScaler<<6)预分频值 channel<<3模拟通道选择
86. delay(1000);
87.
88. }
89.
90. /*************************************************
91. Function name: ReadAdc(int channel)
92. Parameter : int channel
93. Description : 获取AD 转换后的值
94. Return : int
95. Argument : void
96. Autor & date : Daniel
97. **************************************************/
98. int ReadAdc(int channel)
99. {
100.
101. /*开启AD转换*/
102. rADCCON |= 0x01; //start ADC
103.
104.
105. while(rADCCON & 0x1); //check if Enable_start is low
106.
107. while(!(rADCCON & 0x8000)); //check if EC(End of Conversion) flag is high判断转换是否结束
108.
109. return ( (int)rADCDAT0 & 0x3ff );//读取转换后的值
110. }
111. /*************************************************
112. Function name: Set_Clk()
113. Parameter : void
114. Description : 设置CPU的时钟频率
115. Return : void
116. Argument : void
117. Autor & date : Daniel
118. **************************************************/
119. void Set_Clk(void)
120. {
121. int i;
122. U8 key;
123. U32 mpll_val = 0 ;
124. i = 2 ; //don't use 100M!
125. //boot_params.cpu_clk.val = 3;
126. switch ( i ) {
127. case 0: //200
128. key = 12;
129. mpll_val = (92<<12)|(4<<4)|(1);
130. break;
131. case 1: //300
132. key = 13;
133. mpll_val = (67<<12)|(1<<4)|(1);
134. break;
135. case 2: //400
136. key = 14;
137. mpll_val = (92<<12)|(1<<4)|(1);
138. break;
139. case 3: //440!!!
140. key = 14;
141. mpll_val = (102<<12)|(1<<4)|(1);
142. break;
143. default:
144. key = 14;
145. mpll_val = (92<<12)|(1<<4)|(1);
146. break;
147. }
148.
149. //init FCLK=400M, so change MPLL first
150. ChangeMPllValue((mpll_val>>12)&0xff, (mpll_val>>4)&0x3f, mpll_val&3); //set the register--rMPLLCON
151. ChangeClockDivider(key, 12); //the result of rCLKDIVN [0:1:0:1] 3-0 bit
152. cal_cpu_bus_clk(); //HCLK=100M PCLK=50M
153. }
154. /*************************************************
155. Function name: cal_cpu_bus_clk
156. Parameter : void
157. Description : 设置PCLK\HCLK\FCLK的频率
158. Return : void
159. Argument : void
160. Autor & date : Daniel
161. **************************************************/
162. static void cal_cpu_bus_clk(void)
163. {
164. static U32 cpu_freq;
165. static U32 UPLL;
166.
167. U32 val;
168. U8 m, p, s;
169.
170. val = rMPLLCON;
171. m = (val>>12)&0xff;
172. p = (val>>4)&0x3f;
173. s = val&3;
174.
175. //(m+8)*FIN*2 不要超出32位数!
176. FCLK = ((m+8)*(FIN/100)*2)/((p+2)*(1<<s))*100; //FCLK=400M FIN=12000000
177.
178. val = rCLKDIVN;
179. m = (val>>1)&3;
180. p = val&1;
181. val = rCAMDIVN;
182. s = val>>8;
183.
184. switch (m) {
185. case 0:
186. HCLK = FCLK;
187. break;
188. case 1:
189. HCLK = FCLK>>1;
190. break;
191. case 2:
192. if(s&2)
193. HCLK = FCLK>>3;
194. else
195. HCLK = FCLK>>2;
196. break;
197. case 3:
198. if(s&1)
199. HCLK = FCLK/6;
200. else
201. HCLK = FCLK/3;
202. break;
203. }
204.
205. if(p)
206. PCLK = HCLK>>1;
207. else
208. PCLK = HCLK;
209.
210. if(s&0x10)
211. cpu_freq = HCLK;
212. else
213. cpu_freq = FCLK;
214.
215. val = rUPLLCON;
216. m = (val>>12)&0xff;
217. p = (val>>4)&0x3f;
218. s = val&3;
219. UPLL = ((m+8)*FIN)/((p+2)*(1<<s));
220. UCLK = (rCLKDIVN&8)?(UPLL>>1):UPLL;
221. }

这个程序在驱动AD过程中为什么还要设置时钟

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