Microchip Technology dsPIC30F - Page 398

dsPIC30F Family Reference Manual
DS70064C-page 17-22 © 2004 Microchip Technology Inc.
17.12.2.2 Multiple Channels with Simultaneous Sampling
As shown in Figure 17-8 when using simultaneous sampling, the SAMC value specifies the
sampling time. In the example, SAMC specifies a sample time of 3 T
AD. Because automatic
sample start is active, sampling will start on all channels after the last conversion ends and will
continue for 3 A/D clocks. See Example 17-5 for code example.
Figure 17-8: Converting 4 Channels, Auto-Sample Start, T
AD Conversion Start, Simultaneous Sampling
Example 17-5: Converting 4 Channels, Auto-Sample Start,
T
AD Conversion Start, Simultaneous Sampling Code
TCONV TCONV TCONV TCONV
ADCLK
ch1_samp
ch2_samp
ch3_samp
ch0_samp
ADCBUF0
ADCBUF1
ADCBUF2
ADCBUF3
TCONV TCONV
DONE
SAMP
TSAMP
ADPCFG = 0xFF78; // RB0,RB1,RB2 & RB7 = analog
ADCON1 = 0x00EC; // SIMSAM bit = 1 implies ...
// simultaneous sampling
// ASAM = 1 for auto sample after convert
// SSRC = 111 for 3Tad sample time
ADCHS = 0x0007; // Connect AN7 as CH0 input
ADCSSL = 0;
ADCON3 = 0x0302; // Auto Sampling 3 Tad, Tad = internal 2 Tcy
ADCON2 = 0x030C; // CHPS = 1x implies simultaneous ...
// sample CH0 to CH3
// SMPI = 0011 for interrupt after 4 converts
ADCON1bits.ADON = 1; // turn ADC ON
while (1) // repeat continuously
{
ADC16Ptr = &ADCBUF0; // initialize ADCBUF pointer
OutDataPtr = &OutData[0]; // point to first TXbuffer value
IFS0bits.ADIF = 0; // clear interrupt
while (IFS0bits.ADIF); // conversion done?
for (count = 0; count < 4; count++) // save the ADC values
{
ADCValue = *ADC16Ptr++;
LoadADC(ADCValue);
}
} // repeat