什么是DMA直接内存访问

理论上，DMA应该用来自ADC的样本填充缓冲器而不需要CPU的任何干预：当缓冲区满了（比如：1KWord）时，你会有一些标志提升，然后你就可以处理这些数据…同时，ADC/DMA-QIL将为您填充另一个缓冲区。基本上，减少50%的时间。通常需要一些缓冲的乒乓方法，计时器可以用来在给定的间隔触发ADC（和DMA）。我想说这一切都取决于你使用的图片：我正试图在DSPIC33 E上做一些类似的事情…



      以下为原文

    In theory, DMA should fill a buffer with samples coming from the ADC without any intervention by the CPU: when the buffer is full (say: 1Kwords) you have some flag raisen and then you can process that data... and meanwhile the ADC/DMA qill be filling another buffer for you.
Basically, cutting 50% of the time. Some buffers ping-pong method is usually needed.
 
The timer could be used to trigger ADC (and hence DMA) at given intervals. I'd say it all may depend upon the PIC you use: I am trying to make up something similar on a dsPIC33E ...

5）使用中断或DMA的ADC最快的方法是什么？6）DSPIC33 EP512MU810具有两个ADC模块。我可以使用ADC 1在5个信道和ADC 2上进行轮询，用于2个信道吗？



      以下为原文

    5) What will be fastest method to use ADC 
with Interrupts or with DMA? 

6) Dspic33ep512MU810 has two ADC Modules. Can I use ADC 1 on Polling for 5 channels and 
ADC 2 with DMA for for 2 Channels? 
 
 

嗨，我已经看到例子16-8:ADC配置代码从DSSPIC33 EP FRMDS70621C。现在我正在阅读所有12个通道的顺序读取轮询ADDF位，但我的要求如下：RB0＆LT；AN0＆GT；Low Speed Sample /转换所需[与轮询过程] RB1＆LT；AN1＆GT；与DMA[SPE高]ED样本/转换要求[RB2＆lt；AN2＆Gt；Low Speed Sample /转换] [轮询过程] RB3＆LT；AN3＆Gt；Low Speed Sample /转换所需[轮询过程] RB4＆LT；AN4＆GT；Low Speed Sample /转换所需[轮询过程] RB5＆LT；AN5＆GT；Low Speed Sample /转换要求D[用轮询过程] RB6& lt；AN6& GT；DMA [高速采样/转换要求] RB7& lt；AN7＆GT；Low Speed Sample /转换所需[轮询过程] RB8＆LT；AN8＆GT；Low Speed Sample /转换所需[轮询过程] RB9＆LT；AN9＆GT /转换所需[与轮询]过程[RB10＆L]；AN10＆GT；Low Speed Sample /转换所需的[轮询过程] RB11 & lt；AN11＆Gt；Low Speed Sample /转换所需的[轮询过程] WHEDMA0DISTICTY发生在ADC结果将被CPU保存的情况下？如何在主函数或其他函数中使用该值？——TS9



      以下为原文

    Hi, 
 
I have seen Example 16-8: ADC Configuration Code for 1.1 Msps from dsPIC33EP FRM DS70621C.
Now I am reading all 12 channel by sequential read polling ADIF bit but my requirement in as Below:
 
RB0 Low Speed Sample/Conversion Required [With Polling Process]
RB1 With DMA [High Speed Sample/Conversion Required]
RB2 Low Speed Sample/Conversion Required [With Polling Process]
RB3 Low Speed Sample/Conversion Required [With Polling Process]
RB4 Low Speed Sample/Conversion Required [With Polling Process]
RB5 Low Speed Sample/Conversion Required [With Polling Process]
RB6 With DMA [High Speed Sample/Conversion Required]
RB7 Low Speed Sample/Conversion Required   [With Polling Process]
RB8 Low Speed Sample/Conversion Required   [With Polling Process]
RB9 Low Speed Sample/Conversion Required   [With Polling Process]
RB10Low Speed Sample/Conversion Required [With Polling Process]
RB11Low Speed Sample/Conversion Required [With Polling Process]
 

dsPIC33E/PIC24E Family Reference Manual Page DS70621C-page 16-58
#include
/** CONFIGURATION **************************************************/
_FOSCSEL(FNOSC_FRC);
_FOSC(FCKSM_CSECMD & POSCMD_XT & OSCIOFNC_OFF & IOL1WAY_OFF);
_FWDT(FWDTEN_OFF);
_FPOR(FPWRT_PWR128 & BOREN_ON & ALTI2C1_ON & ALTI2C2_ON);
_FICD(ICS_PGD1 & RSTPRI_PF & JTAGEN_OFF);
void initAdc1(void);
void initDma0(void);
void Delay_us(unsigned int);
int BufferA[8] = {0, 0, 0, 0, 0, 0, 0, 0};
int BufferB[8] = {0, 0, 0, 0, 0, 0, 0, 0};
int i;
int main(void)
{
// Configure the device PLL to obtain 40 MIPS operation. The crystal frequency is 8 MHz.
// Divide 8 MHz by 2, multiply by 40 and divide by 2. This results in Fosc of 80 MHz.
// The CPU clock frequency is Fcy = Fosc/2 = 40 MHz.
PLLFBD = 38; /* M = 40 */
CLKDIVbits.PLLPOST = 0; /* N1 = 2 */
CLKDIVbits.PLLPRE = 0; /* N2 = 2 */
OSCTUN = 0;
/* Initiate Clock Switch to Primary Oscillator with PLL (NOSC = 0x3) */
__builtin_write_OSCCONH(0x03);
__builtin_write_OSCCONL(0x01);
while (OSCCONbits.COSC != 0x3);
while (_LOCK == 0); /* Wait for PLL lock at 40 MIPS */
initAdc1();
initDma0();
while(1); /* Wait for DMA interrupts to occur */
}
void initAdc1(void)
{
/* Set port configuration */
ANSELA = ANSELC = ANSELD = ANSELE = ANSELG = 0x0000;
ANSELB = 0x0001; // Ensure AN0 is analog
/* Initialize ADC module */
AD1CON1 = 0x13E4; // DMA Conversion Order, sequential sampling, 10-bit, Signed Fractional
AD1CON2 = 0x0100; // Select 2-channel mode, increment DMA pointer after every sample
AD1CON3bits.ADRC = 0;// ADC Clock is derived from System Clock
AD1CON3bits.SAMC = 2; // Sample for 2 * Tad before converting
AD1CON3bits.ADCS = 2; // TAD= TCY* (ADCS + 1) = (1 / 40MHz) * 3 = 75 ns (13.3 MHz)
// ADC conversion time for 10-bit Tconv = 12 * Tad = 900 ns (1.1 Msps)
AD1CON4 = 0x0100; // Use DMA to store conversion results
AD1CSSH = 0x0000;
AD1CSSL = 0x0000;
/* Assign MUXA inputs */
AD1CHS0bits.CH0SA = 0; // Select AN0 for CH0 +ve input
AD1CHS0bits.CH0NA = 0; // Select VREF- for CH0 -ve input
AD1CHS123bits.CH123SA = 0; // Select AN0 for CH1 +ve input
AD1CHS123bits.CH123NA = 0; // Select VREF- for CH1 -ve input
/* Enable ADC module and provide ADC stabilization delay */
AD1CON1bits.ADON = 1;
Delay_us(20);
}
void __attribute__((interrupt, auto_psv)) _DMA0Interrupt(void)
{
_DMA0IF = 0; /* Clear DMA interrupt flag to prepare for next block */
}
void Delay_us(unsigned int delay)
{
for (i = 0; i < delay; i++)
{
__asm__ volatile ("repeat #39");
__asm__ volatile ("nop");
}
}

When DMA0Interrupt is occurred where ADC result will save by CPU ?
How to use that value in main or any other function ?
 
--
TS9
 

IndDMA（）函数在哪里？



      以下为原文

    Where is initDMA() function?

感谢不写在DSPIC33 EP FRMDS70621Cand从CE420AADCCHCHSCAN MHCP演示



      以下为原文

    Thanks Not Written in  dsPIC33EP FRM DS70621C
and  taken from ce420_adc_chscan MHCP Demos

void InitDma0( void )
{
DMA0CONbits.AMODE = 2; // Configure DMA for Peripheral indirect mode
DMA0CONbits.MODE = 2; // Configure DMA for Continuous Ping-Pong mode
DMA0PAD = ( int ) &ADC1BUF0;
DMA0CNT = ( SAMP_BUFF_SIZE * NUM_CHS2SCAN ) - 1;
DMA0REQ = 13; // Select ADC1 as DMA Request source
#ifdef _HAS_DMA_
DMA0STAL = __builtin_dmaoffset( &bufferA );
DMA0STAH = __builtin_dmapage( &bufferA );
DMA0STBL = __builtin_dmaoffset( &bufferB );
DMA0STBH = __builtin_dmapage( &bufferB );
#else
DMA0STAL = ( uint16_t ) ( &bufferA );
DMA0STAH = ( uint16_t ) ( &bufferA );
DMA0STBL = ( uint16_t ) ( &bufferB );
DMA0STBH = ( uint16_t ) ( &bufferB );
#endif
IFS0bits.DMA0IF = 0; //Clear the DMA interrupt flag bit
IEC0bits.DMA0IE = 1; //Set the DMA interrupt enable bit
DMA0CONbits.CHEN = 1; // Enable DMA
}

好！有道理，所以你应该找到你的数据



      以下为原文

    Good! Makes sense
So you should find your data in
bufferA
and bufferB
(the ping-pong method)

.



      以下为原文

    .

一个频道？具体渠道如何？多一个渠道？



      以下为原文

    For One Channel ?
How to particular channel ? more then one channel ? 

MHCP DEMOS AT1）CE401- ADC采样在1.1MSPs与DMA（无定时器）2）CE420-ADC信道扫描与DMA（定时器）与计时器我理解？没有定时器，阅读间隔可以得到什么？



      以下为原文

    MHCP Demos at 
1) CE401 - ADC Sampling at 1.1MSPS with DMA(without Timers)
2) CE420 - ADC Channel Scanning with DMA(with Timers)
With Timer  I understand ?
Without Timer, After what interval reading can get ?

DMA缓冲器被分配给特定的ADC。如果这个ADC ISS分配了一些顺序采样，那么你会在同一个DMA缓冲器（块）中找到这些通道的值——一个接一个。一个计时器可以用来触发单独的转换-以达到低于最大转换率的一些采样率。或者将ADC转换与来自相同定时器（例如PWM）的其他活动同步。



      以下为原文

    The DMA  buffers are assigned to a specific ADC. If this ADC iss assigned some sequential sampling, you'll find the values of these channels in the same DMA buffer (block) - one after the other.
A timer can be used to trigger individual conversions - to achieve some sampling rate lower than the maximum conversion rate. Or to synchronize ADC conversions with other activities derived from the same timer (e.g. PWM).

好的，谢谢。四个通道和十二个通道的总CPU时间与DMA相同。如何用DMA来计算？与Fosc @ 120兆赫。——TS9



      以下为原文

    Ok Thanks..
The Total CPU time of reading for four channels and twelve channels will be same with DMA.?
How to calculate that with DMA?
With Fosc @120Mhz.
--
TS9

“阅读时间”被理解为“ADC转换时机”？如果是的话，也许你还没有得到“DMA点”：DMA传输正在发生，否则会发生中断-需要MCU交互。简单地从一些数据传输卸载MCU。



      以下为原文

    "time of reading" to be understood as "ADC conversion timing"? If so: yes.
Maybe you didn't yet get the "DMA point": a DMA transfer is taking place where otherwise an interrupt would occur - requiring MCU interaction. Simply offloading the MCU from some data transfers.

我认为我应该更快地需要与DMA和轮询休息（ADC模块2）对话2个通道（ADC模块1）？



      以下为原文

    I think I should go faster need conversation 2 channels( with ADC Module 1) with DMA and rest of Polling (ADC Module 2) ?

DSPIC33 EP 10位ADC。自动采样和自动转换选项在不检查ADIF位的情况下工作吗？内循环



      以下为原文

    Dspic33ep 10-bit ADC. Will auto sampling and auto conversion options worked without checking ADIF bit continuously ? In while Loop

由于每个ANX都有一个结果寄存器，所以我希望如此。考虑到这些ADC的复杂性，我建议咨询ADS的数据表7000 05213。



      以下为原文

    As there exists a result register for each ANx, I expect so.
Given the complexity of these ADCs, I suggest to consult DS70005213 - the ADCs' datasheet.