test/periph_dac: adds a test for DACs

tests/periph_dac/Makefile

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+APPLICATION = periph_dac
+include ../Makefile.tests_common
+
+FEATURES_REQUIRED = periph_dac
+USEMODULE += vtimer
+
+include $(RIOTBASE)/Makefile.include

tests/periph_dac/README.md

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+About
+=====
+This is a test application for a digital to analog converter (DAC).
+
+This test application will initialize each configured DAC and one ADC (ADC_O) device to sample with
+10-bit accuracy. The ADC is only initialized if there is one available on your board.
+
+After initialization, values from 0 to 1000 are converted through the DACs in a loop. Shortly after the digital to analog conversion of one number, the ADC_0 samples its input signal. The numbers that are given to the DACs and the numbers that are sampled by the ADC were printed to the STDOUT. 
+
+Usage
+=====
+
+a) Connect an oscilloscope to the DAC pins and look at the ten iteration signal levels
+
+or
+
+b) Connect the ADC input to the DAC outputs successively and compare if the sampled input value correlates with the printed output value at each DAC port.

tests/periph_dac/main.c

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+/*
+ * Copyright (C) 2014 Freie Universität Berlin
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser General
+ * Public License v2.1. See the file LICENSE in the top level directory for more
+ * details.
+ */
+
+/**
+ * @ingroup tests
+ * @{
+ *
+ * @file
+ * @brief       Test case for the low-level DAC driver
+ *
+ * @author      Peter Kietzmann <[email protected]>
+ * @author      Hauke Petersen <[email protected]>
+ *
+ * @}
+ */
+
+#include <stdio.h>
+
+#include "cpu.h"
+#include "board.h"
+#include "vtimer.h"
+#include "periph/dac.h"
+#include "periph/adc.h"
+
+#if DAC_NUMOF < 1
+#error "Please enable at least 1 DAC device to run this test"
+#endif
+
+#define RES             DAC_RES_10BIT
+#define DELAY           (1000 * 1000U)
+#define MAX_VALUE_STEPS 1000
+
+static int values[DAC_NUMOF][DAC_MAX_CHANNELS];
+
+int main(void)
+{
+    uint16_t write_value = 0;
+    int8_t status_dac_write;
+
+    puts("\nRIOT DAC peripheral driver test\n");
+    puts("This test simply sets each available DAC channel about every 100ms\n\n");
+
+    for (int i = 0; i < DAC_NUMOF; i++) {
+        /* initialize result vector */
+        for (int j = 0; j < DAC_MAX_CHANNELS; j++) {
+            values[i][j] = -1;
+        }
+        /* initialize DAC device */
+        printf("Initializing DAC_%i @ %i bit resolution", i, (6 + (2* RES)));
+        if (dac_init(i, RES) == 0) {
+            puts("    ...[ok]");
+        }
+        else {
+            puts("    ...[failed]");
+            return 1;
+        }
+
+#if ADC_NUMOF > 0
+        printf("Initializing ADC_0 @ %i bit resolution", (6 + (2* RES)));
+        if (adc_init(0, RES) == 0) {
+            puts("    ...[ok]");
+        }
+        else {
+            puts("    ...[failed]");
+            return 1;
+        }
+#endif
+    }
+    puts("\n");
+
+    while (1) {
+        for (int i = 0; i < DAC_NUMOF; i++) {
+            for (int j = 0; j < DAC_MAX_CHANNELS; j++) {
+                /* Write values to DAC */
+                status_dac_write = dac_write(i, j, write_value);
+                if (status_dac_write < 0) {
+                    printf("%i: Something went wrong writing DAC\n", status_dac_write);
+                    return -1;
+                }
+#if ADC_NUMOF > 0
+                /* Read values from ADC */
+                int sample = adc_sample(ADC_0, 0);
+                if (sample < 0) {
+                    printf("%i: Something went wrong sampling ADC\n", sample);
+                    return -1;
+                }
+                printf("Wrote %i Read %i using DAC %i Channel %i and ADC_0 Channel 0\n", write_value, sample, i, j);
+#else
+                printf("Wrote %i to DAC %i Channel %i\n", write_value, i, j);
+#endif
+            }
+        }
+        puts("\n");
+        write_value+=100;
+        if (write_value >= MAX_VALUE_STEPS) {
+            write_value = 0;
+        }
+        /* sleep a little while */
+        vtimer_usleep(DELAY);
+    }
+
+    return 0;
+}