capture.cpp

/*
 * capture.cpp - ADC data capture
 * Tiny Scope for Arduino project
 *
 * Copyright (C)2015 Laurentiu Badea
 *
 * This file may be redistributed under the terms of the MIT license.
 * A copy of this license has been included with this distribution in the file LICENSE.
 */
#include "capture.h"

int Capture::init(ADCInput adc_in, unsigned samples_in, uint16_t rangemV_in){
    adc = adc_in;
    samples = samples_in;
    rangemV = rangemV_in;
    data = (uint16_t*)calloc(samples+2, sizeof(uint16_t)); // two extra reads: 0 and a non-zero
    if (!data){
        samples = 0;
    }
    return data != 0;
}

/*
 * ADC allowable float for zero-detection (because of unclean ground)
 */
#define ADC_JITTER 4
/*
 * Capture the requested number of samples.
 * on return, data contains the raw capture data.
 */
void Capture::capture(){
    uint32_t start;
    uint16_t *dataCur;
    uint16_t v;
    unsigned j;

    adc.read(); // allow the port to be configured (discard result)

    dataCur = data;
    /*
     * Attempt to latch on a zero transition
     */
    for (j=1024; j; j--){
        v = adc.readFast();
        if (v < ADC_JITTER){
            *dataCur++ = v;
            break;
        }
    }
    for (j=1024; j; j--){
        v = adc.readFast();
        if (v >= ADC_JITTER){
            *dataCur++ = v;
            break;
        } else {
            *data = v; // overwrite a previous "0" at dataCur-1
        }
    }
    start = micros();
    adc.readMulti(dataCur, samples);
    elapsedus = micros() - start;
}

/*
 * Convert captured data to mV and extract min/max values
 */
void Capture::tomV(){
    uint16_t v;
    minmV = rangemV;
    maxmV = 0;
    for (unsigned i=0; i<samples; i++){
        v = map(data[i], 0, (1L<<adc.bits)-1, 0, long(rangemV));
        data[i] = v;
        if (v < minmV){
            minmV = v;
        };
        if (v > maxmV){
            maxmV = v;
        }
    }
}