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Board index » 產品技術問題 (開版時請註明使用的元件編號及C編譯器版本) » » 16-bit PIC24/dsPIC® Device » dsPIC30F6012A的12位ADC的疑问???


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meng_1226
Re: dsPIC30F6012A的12位ADC的疑问???
#5
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多谢版主指点!

發表於: 2008/1/7 20:52
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Ryang
Re: dsPIC30F6012A的12位ADC的疑问???
#4
版主
版主


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1. 兩種方式適用的時機不一樣，高速轉換 < 500uS 時，可以用內部時續做自動取樣及轉換。但轉換速度較慢時就要考慮用 Timer3 的觸發轉換。原因是因為 System Clock 無法用 ADCON3<ADCS 5:0> 將Tcy 降的很低。

2. 那就直接掃描 10ch 後產生中斷，自己在 ADCBUF0 ~ADCBUF9 裡取出所要用的資料，這樣比較簡單。當然你可以用 Altemate 切換模式選擇 A/B 兩組的輸入切換，但這樣做比較麻煩，程式也較複雜。

發表於: 2008/1/7 10:43
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meng_1226
Re: dsPIC30F6012A的12位ADC的疑问???
#3
新會員
新會員


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多谢版主,
但教材是10位AD,我用的是12位AD,只有一个S/H通道
看了教材之后还有两个问题请版主再来指点一下!

1.用Timer3方式和自动采样自动转换方式哪一种方式更好一点呢?
用Timer3方式时间更精准吗?
我用的自动采样自动转换方式是想省一个Timer3定时器资源
2.比如我想10路AD,(an0~an9)
我想只扫描8路,第一次是an0~an5,an6,an7,
第二次是an0~an5,an8,an9,这样反复,然后每8次中断一次
我这样在中断里切换扫描通道可以,时间能保存准确吗?
void InitADC(void)
{
ADCON1bits.ADON = 0;

ADCHS = 0x0000;

IPC2bits.ADIP = 7; // highest
IFS0bits.ADIF = 0;
IEC0bits.ADIE = 1;

ADPCFGbits.PCFG0 = 0; // an0~an9,diagal ad
ADPCFGbits.PCFG1 = 0;
ADPCFGbits.PCFG2 = 0;
ADPCFGbits.PCFG3 = 0;
ADPCFGbits.PCFG4 = 0;
ADPCFGbits.PCFG5 = 0;
ADPCFGbits.PCFG6 = 0;
ADPCFGbits.PCFG7 = 0;
ADPCFGbits.PCFG8 = 0;
ADPCFGbits.PCFG9 = 0;
ADPCFGbits.PCFG10 = 1;
ADPCFGbits.PCFG11 = 1;
ADPCFGbits.PCFG12 = 1;
ADPCFGbits.PCFG13 = 1;
ADPCFGbits.PCFG14 = 1;
ADPCFGbits.PCFG15 = 1;

ADCSSLbits.CSSL0 = 0; //first scan an0~an7
ADCSSLbits.CSSL1 = 0;
ADCSSLbits.CSSL2 = 0;
ADCSSLbits.CSSL3 = 0;
ADCSSLbits.CSSL4 = 0;
ADCSSLbits.CSSL5 = 0;
ADCSSLbits.CSSL6 = 0;
ADCSSLbits.CSSL7 = 0;
ADCSSLbits.CSSL8 = 1;
ADCSSLbits.CSSL9 = 1;
ADCSSLbits.CSSL10 = 1;
ADCSSLbits.CSSL11 = 1;
ADCSSLbits.CSSL12 = 1;
ADCSSLbits.CSSL13 = 1;
ADCSSLbits.CSSL14 = 1;
ADCSSLbits.CSSL15 = 1;

ADCON3bits.SAMC = 11; //Tsamp=11Tad,Tconv=14Tad
ADCON3bits.ADCS = 19; //Tad=10Tcy Tsamp=13.75us,Tconv=17.5us

ADCON2bits.VCFG = 0; // AVDD AVSS
ADCON2bits.CSCNA = 1; // Scan
ADCON2bits.SMPI = 7; //Pre8 interrupt
ADCON2bits.BUFM = 0; //16Word
ADCON2bits.ALTS = 0; //mux A

ADCON1bits.FORM = 0; //unsigned integer
ADCON1bits.SSRC = 9; //auto convert
ADCON1bits.ASAM = 1; //auto sample

ADCON1bits.ADON = 1;

}

void __attribute__ ((interrupt, no_auto_psv)) _ADCInterrupt(void)
{
IFS0bits.ADIF = 0;
if(!ADCSSLbits.CSSL8)
{
ADCSSLbits.CSSL0 = 0; //first scan an0~an7
ADCSSLbits.CSSL1 = 0;
ADCSSLbits.CSSL2 = 0;
ADCSSLbits.CSSL3 = 0;
ADCSSLbits.CSSL4 = 0;
ADCSSLbits.CSSL5 = 0;
ADCSSLbits.CSSL6 = 0;
ADCSSLbits.CSSL7 = 0;
ADCSSLbits.CSSL8 = 1;
ADCSSLbits.CSSL9 = 1;
ADCSSLbits.CSSL10 = 1;
ADCSSLbits.CSSL11 = 1;
ADCSSLbits.CSSL12 = 1;
ADCSSLbits.CSSL13 = 1;
ADCSSLbits.CSSL14 = 1;
ADCSSLbits.CSSL15 = 1;
}
else
{
ADCSSLbits.CSSL0 = 0; //second scan an0~an7
ADCSSLbits.CSSL1 = 0;
ADCSSLbits.CSSL2 = 0;
ADCSSLbits.CSSL3 = 0;
ADCSSLbits.CSSL4 = 0;
ADCSSLbits.CSSL5 = 0;
ADCSSLbits.CSSL6 = 1;
ADCSSLbits.CSSL7 = 1;
ADCSSLbits.CSSL8 = 0;
ADCSSLbits.CSSL9 = 0;
ADCSSLbits.CSSL10 = 1;
ADCSSLbits.CSSL11 = 1;
ADCSSLbits.CSSL12 = 1;
ADCSSLbits.CSSL13 = 1;
ADCSSLbits.CSSL14 = 1;
ADCSSLbits.CSSL15 = 1;
}
}

發表於: 2008/1/5 9:59
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Ryang
Re: dsPIC30F6012A的12位ADC的疑问???
#2
版主
版主


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因為你的取樣時間算蠻慢的，可以考慮使用 Timer3 的 Trigger 來觸發 ADC 做轉換。　在 dsPIC30F Peripheral Module - 10-bit ADC　裡的教材裡有利用 Timer3來觸發 ADC 的範例，也有用 Syatem Clock 做自動取樣的範例。

另外有關 Tsamp & Tconv　的說明在這獎以的後面也有詳細的說明與使用方式。
http://www.microchip.com.tw/modules/mydownloads/viewcat.php?cid=4

發表於: 2008/1/4 14:52
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meng_1226
dsPIC30F6012A的12位ADC的疑问???
#1
新會員
新會員


查看用戶資訊
如果用自动采样自动转换方式的话,那个Tsamp与Tconv怎样设置才好一点!
比如我扫描10路AD,每路都是20ms内采样64个点,每10次采样/转换过程中断一次,
假设Fcy=8000000,我的程序如下:

#define CHANNUM 10
#define SAMPNUM 64

uint g_Samples[CHANNUM][SAMPNUM]
void InitADC1(void)
{
fAdcDone = FALSE;
ADCON1bits.ADON = 0;

ADCHS = 0x0000;

IPC2bits.ADIP = 7; // highest
IFS0bits.ADIF = 0;
IEC0bits.ADIE = 1;

ADPCFG = 0xC8D0; //an0~an3,an5,an8~an10,an12,an13
ADCSSL = 0x372F;

ADCON3bits.SAMC=6; //Tsamp=6Tad,Tconv=14Tad
ADCON3bits.ADCS=24; //Tad=12.5Tcy Tsamp=9.375us,Tconv=21.875us

ADCON2bits.VCFG = 0; // AVDD AVSS
ADCON2bits.CSCNA=1; // Scan
ADCON2bits.SMPI=9; //Pre10 interrupt
ADCON2bits.BUFM=0; //16Word
ADCON2bits.ALTS=0; //mux A

ADCON1bits.FORM=0; //unsigned integer
ADCON1bits.SSRC=9; //auto convert
ADCON1bits.ASAM=1; //auto sample

ADCON1bits.ADON = 1;
}


void InitADC2(void)
{
fAdcDone = FALSE;
ADCON1bits.ADON = 0;

ADCHS = 0x0000;

IPC2bits.ADIP = 7; // highest
IFS0bits.ADIF = 0;
IEC0bits.ADIE = 1;

ADPCFG = 0xC8D0; //an0~an3,an5,an8~an10,an12,an13 10 channel
ADCSSL = 0x372F;

ADCON3bits.SAMC=11; //Tsamp=11Tad,Tconv=14Tad
ADCON3bits.ADCS=19; //Tad=10Tcy Tsamp=13.75us,Tconv=17.5us

ADCON2bits.VCFG = 0; // AVDD AVSS
ADCON2bits.CSCNA=1; // Scan
ADCON2bits.SMPI=9; //Pre10 interrupt
ADCON2bits.BUFM=0; //16Word
ADCON2bits.ALTS=0; //mux A

ADCON1bits.FORM=0; //unsigned integer
ADCON1bits.SSRC=9; //auto convert
ADCON1bits.ASAM=1; //auto sample

ADCON1bits.ADON = 1;
}

void __attribute__ ((interrupt, no_auto_psv)) _ADCInterrupt(void)
{
IFS0bits.ADIF = 0;

static int iLoopCount = 0;

int i;
uint *p;
//pre10 interrupt get 10 adcvalue==ADCBUF0~ADCBUF9
p = (uint *) & ADCBUF0;
for(i = 0; i < CHANNUM; i++)
g_Samples[i][iLoopCount] = *p++;

// Cycle SAMPNUM=64 20ms
if(++iLoopCount >= SAMPNUM)
{
iLoopCount = 0;
fAdcDone = TRUE;
}
}

用InitADC1()方式设置的Tsamp和Tconv好
还是用InitADC2()方式设置的Tsamp和Tconv好呢?
Tsamp与Tconv的时间选择这个问题一直困扰着我?
喜欢哪位大侠给讲讲了?

發表於: 2008/1/4 13:34
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Board index » 產品技術問題 (開版時請註明使用的元件編號及C編譯器版本) » » 16-bit PIC24/dsPIC® Device » dsPIC30F6012A的12位ADC的疑问???


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