Mario Bambagini
Program for reading data from one (or two) ACS712 (current sense amplifier). Read the configuration before trying it.
This program aims at implementing a simple current reader which, sensing from an ACS712, prints on the USB port the average of n samples.
The program can be configured at compile-time by setting few defines:
- the number of channels: either only p20 or the sum of p19 and p20;
- the number of samples to read before printing their average
- the operating mode:
- PIN_TRIGGERED: read a handful of samples when the pin p9 rises
- USER_TRIGGERED: start reading when the user presses the character 's'
- ENDLESS_READ: read continuosly
First of all, when the program starts, it read a bunch of samples and then sets their mean value as reference. This means that the software assumes that when such a reference value is read, there is no current absorption.
Diff: main.cpp
- Revision:
- 0:36d465acb1a2
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp Tue Mar 12 12:20:25 2013 +0000
@@ -0,0 +1,133 @@
+/**********************************************************
+ * CONFIGURATION: before starting, configure the reader
+ **********************************************************/
+
+//define the number of channels to use:
+// -) 1 channel: p20
+// -) 2 channels: p19 and p20
+#define NCHANNELS 1
+//#define nChannels 1
+
+//number of samples to read before printing their average
+#define NSAMPLES 2500
+
+//number of samplng operation after an user trigger
+//(total samples: NSAMPLES*NSAMPLING)
+#define NSAMPLING 50
+
+//read NSAMPLES values when the pin p9 is high
+#define PIN_TRIGGERED 2
+
+//the sampling is run only when the user presses the character 's'
+//the operation lasts for NSAMPLING iterations
+#define USER_TRIGGERED 1
+
+//read all the time
+#define ENDLESS_READ 0
+
+#define ACQ_TYPE USER_TRIGGERED
+
+
+/**********************************************************
+ * CONFIGURATION CHECK
+ **********************************************************/
+#if !defined(NCHANNELS) || (NCHANNELS!=1 && NCHANNELS!=2)
+#error "The number of channels is wrong"
+#endif
+
+#if !defined(ACQ_TYPE) || (ACQ_TYPE!=ENDLESS_READ && \
+ ACQ_TYPE!=PIN_TRIGGERED && ACQ_TYPE!=USER_TRIGGERED)
+#error "Acquisition type not detected or not valid"
+#endif
+
+#if ACQ_TYPE==USER_TRIGGERED && !defined(NSAMPLING)
+#error "Define a number of samplings after the user trigger"
+#endif
+
+
+/**********************************************************
+ * CODE
+ **********************************************************/
+
+#include "mbed.h"
+
+AnalogIn ain_1(p20);
+#if NCHANNELS==2
+AnalogIn ain_2(p19);
+#endif
+
+#if ACQ_TYPE==PIN_TRIGGERED
+DigitalIn firer (p9);
+#endif
+
+#define V_max 3.3
+
+int main()
+{
+ double vref_1 = 0.0;
+#if NCHANNELS==2
+ double vref_2 = 0.0;
+#endif
+
+ //acquiring v_ref
+ for (int i=0; i<NSAMPLES; i++) {
+ vref_1 += ain_1;
+#if NCHANNELS==2
+ vref_2 += ain_2;
+#endif
+ }
+ vref_1 /= NSAMPLES;
+ printf("Vref 1: %f\n\r", vref_1);
+#if NCHANNELS==2
+ vref_2 /= NSAMPLES;
+ printf("Vref 2: %f\n\r", vref_2);
+#endif
+
+ //main loop
+ while(true) {
+ //start condition
+#if ACQ_TYPE==USER_TRIGGERED
+ printf("press \'s\' to start\n\r");
+ int c;
+ do {
+ c = getchar();
+ } while (c!='s');
+ for (int i=0; i<NSAMPLING; i++) {
+#elif ACQ_TYPE==PIN_TRIGGERED
+ while(firer==0);
+#elif ACQ_TYPE==ENDLESS_READ
+#else
+//already signaled
+//#error "Acquisition type not detected"
+#endif
+
+ //acquisition
+ double sum_1 = 0.0;
+#if NCHANNELS==2
+ double sum_2 = 0.0;
+#endif
+ for (int samples = 0; samples<NSAMPLES; samples++) {
+ sum_1 += ain_1;
+#if NCHANNELS==2
+ sum_2 += ain_2;
+#endif
+ }
+ sum_1 /= NSAMPLES;
+ sum_1 = (sum_1-vref_1)*V_max/0.185;
+#if NCHANNELS==2
+ sum_2 /= NSAMPLES;
+ sum_2 = (sum_2-vref_2)*V_max/0.185;
+ printf("%f\n\r", sum_1+sum_2);
+#else
+ printf("%f\n\r", sum_1);
+#endif
+
+ //final condition
+#if ACQ_TYPE==USER_TRIGGERED
+ }
+#elif ACQ_TYPE==PIN_TRIGGERED
+#elif ACQ_TYPE==ENDLESS_READ
+#else
+#endif
+ }
+}