Specifications

dsPIC33F Family Reference Manual

Example 16-2: Converting 1 Channel, Automatic Sample Start,

Manual Conversion Start Code

16.11.2 Clocked Conversion Trigger

When SSRC<2:0> =

111

, the conversion trigger is under A/D clock control. The Auto Sample Time

(SAMC<4:0>) bits (AD1CON3<12:8>) select the number of T

clock cycles between the start of sam-

pling and the start of conversion. This trigger option provides the fastest conversion rates on multiple

channels. After the start of sampling, the ADC module counts a number of T

clocks specified by the

SAMC bits.

Equation 16-2: Clocked Conversion Trigger Time

When using only one Sample/Hold channel or simultaneous sampling, SAMC must always be pro-

grammed for at least one clock cycle. When using multiple Sample/Hold channels with sequential

sampling, programming SAMC for zero clock cycles results in the fastest possible conversion rate.

See Example 16-3 for code example.

Figure 16-7: Converting 1 Channel, Manual Sample Start, TAD Based Conversion Start

AD1PCFGL = 0xFF7F; // all PORTB = Digital but RB7 = analog

AD1CON1 = 0x0004; // ASAM bit = 1 implies sampling ..

// starts immediately after last

// conversion is done

AD1CHS0= 0x0007; // Connect RB7/AN7 as CH0 input ..

// in this example RB7/AN7 is the input

AD1CSSL = 0;

AD1CON3 = 0x0002; // Sample time manual, Tad = internal 2 Tcy

AD1CON2 = 0;

AD1CON1bits.ADON = 1; // turn ADC ON

while (1) // repeat continuously

{

DelayNmSec(100); // sample for 100 mS

AD1CON1bits.SAMP = 0; // start Converting

while (!AD1CON1bits.DONE);// conversion done?

ADCValue = ADC1BUF0; // yes then get ADC value

} // repeat

TSMP = SAMC<4:0>*TAD

ADC Clock

SAMP

ADC1BUF0

TSAMP

TCONV

BSET AD1CON1,SAMP

Instruction Execution

DONE

= 16 TAD