Add an example which stores data into a MySQL database

Makefile

@@ -1,14 +1,25 @@
 CC=gcc
 CFLAGS=-I. -Werror -pthread -g
+LDFLAGS=-lm -lpthread
+
+MYSQL_CFLAGS=`mysql_config --cflags`
+MYSQL_LDFLAGS=`mysql_config --libs`
+
 DEPS = lngpio.h air_utils.h
 OBJ = lngpio.o air_utils.o test.o
 OBJ_ASYNC = lngpio.o air_utils.o test_async.o
+OBJ_MYSQL = lngpio.o air_utils.o test_mysql.o
 
 %.o: %.c $(DEPS)
 	$(CC) -c -o $@ $< $(CFLAGS)
 
 test: $(OBJ)
-	gcc -o $@ $^ $(CFLAGS) -lm -lpthread
+	gcc -o $@ $^ $(CFLAGS) $(LDFLAGS)
 
 test_async:  $(OBJ_ASYNC)
-	gcc -o $@ $^ $(CFLAGS) -lm -lpthread
+	gcc -o $@ $^ $(CFLAGS) $(LDFLAGS)
+
+test_mysql:  CFLAGS := $(MYSQL_CFLAGS)
+test_mysql:  LDFLAGS := $(MYSQL_LDFLAGS)
+test_mysql:  $(OBJ_MYSQL)
+	gcc -o $@ $^ $(CFLAGS) $(LDFLAGS)

README

@@ -22,7 +22,25 @@ OR
 make test_async
 ./test_async
 
-lngpio provides two APIs:
+OR
+
+make test_mysql
+./test_mysql
+
+./test_mysql stores data into a MySQL database so that it can be later retrieved
+and plotted for example. For the test app to work set up the database in the
+following way:
+
+mysql -h localhost -u root -ppass
+mysql> CREATE DATABASE AirQuality;
+mysql> use AirQuality;
+mysql> CREATE TABLE ParticlePM25 (concentration_pcs FLOAT, \
+    concentration_ugm3 FLOAT, aqi INT, ts_created TIMESTAMP);
+mysql> quit
+Bye
+
+All test applications use lngpio which is part of the project, it provides two
+APIs for reading the GPIO:
 
 1. synchronous API with a pulseIn alike function, ./test uses that one
 2. asyncronous API with callbacks, ./test_async demontrates how to use it

test_mysql.c

@@ -0,0 +1,160 @@
+/*
+ * (c) 2016 Ognyan Tonchev otonchev@gmail.com
+ * Example application monitoring Fine particle (PM2.5) with Grove Dust sensor
+ * (Shinyei PPD42NS) and a Raspberry Pi.
+ * The app uses lngpio's asynchronous API.
+ */
+#include "lngpio.h"
+#include "air_utils.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <math.h>
+
+/* MySQL headers */
+#include <my_global.h>
+#include <mysql.h>
+
+#define LOW  0
+#define HIGH 1
+
+#define PIN  17
+
+/* MySQL database setup */
+#define MYSQL_DATABASE "AirQuality"
+#define MYSQL_USER "root"
+#define MYSQL_PASS "pass"
+
+static unsigned long starttime;
+static unsigned long sampletime_ms = 30000; /* 30s */
+static unsigned long lowpulseoccupancy;
+static struct timeval t_low, t_high;
+
+static long
+millis ()
+{
+  struct timeval  tv;
+  gettimeofday (&tv, NULL);
+
+  return (tv.tv_sec) * 1000 + (tv.tv_usec) / 1000 ;
+}
+
+static void
+finish_with_error (MYSQL *con)
+{
+  fprintf (stderr, "%s\n", mysql_error (con));
+  mysql_close (con);
+  exit (1);
+}
+
+static void
+store_data (float concentration_pcs, float concentration_ugm3, int aqi)
+{
+  MYSQL *con = mysql_init (NULL);
+  char query[1024];
+
+  if (con == NULL) {
+      fprintf (stderr, "%s\n", mysql_error (con));
+      exit (1);
+  }
+
+  if (mysql_real_connect (con, "localhost", MYSQL_USER, MYSQL_PASS,
+      MYSQL_DATABASE, 0, NULL, 0) == NULL) {
+      finish_with_error (con);
+  }
+
+  sprintf (query, "INSERT INTO ParticlePM25 (concentration_pcs,"
+      " concentration_ugm3, aqi) VALUES (%f, %f, %d)",
+      concentration_pcs, concentration_ugm3, aqi);
+
+  if (mysql_query (con, query)) {
+      finish_with_error (con);
+  }
+
+  mysql_close (con);
+}
+
+static void
+pulse_detected (unsigned long pulse_duration)
+{
+  lowpulseoccupancy = lowpulseoccupancy + pulse_duration;
+
+  if ((millis () - starttime) > sampletime_ms) {
+    float ratio;
+    float concentration_pcs;
+    float concentration_ugm3;
+    int aqi;
+
+    ratio = lowpulseoccupancy / (sampletime_ms * 10.0);
+    concentration_pcs =
+        1.1 * pow (ratio, 3) - 3.8 * pow (ratio, 2) + 520 * ratio + 0.62;
+    concentration_ugm3 = pm25pcs2ugm3 (concentration_pcs);
+    aqi = pm25ugm32aqi (concentration_ugm3);
+
+    printf ("%f pcs/0.01cf, %f μg/m3, %d AQI\n", concentration_pcs,
+        concentration_ugm3, aqi);
+
+    store_data (concentration_pcs, concentration_ugm3, aqi);
+
+    lowpulseoccupancy = 0;
+    starttime = millis ();
+  }
+}
+
+static void
+status_changed (int pin, int status)
+{
+  long micros;
+
+  if (status == 0) {
+    gettimeofday (&t_low, NULL);
+  } else if (status == 1) {
+    gettimeofday (&t_high, NULL);
+
+    micros = (t_high.tv_sec - t_low.tv_sec) * 1000000L;
+    micros += (t_high.tv_usec - t_low.tv_usec);
+
+    if (micros > 95000 || micros < 8500)
+      printf ("pulse duration out of bounds: %ld\n", micros);
+
+    pulse_detected (micros);
+  }
+}
+
+int
+main (int argc, char * argv[])
+{
+  LNGPIOPinMonitor *monitor;
+
+  if (lngpio_is_exported (PIN))
+    lngpio_unexport (PIN);
+
+  if (-1 == lngpio_export (PIN))
+    return (1);
+
+  if (-1 == lngpio_wait_for_pin (PIN))
+    return (1);
+
+  if (-1 == lngpio_set_direction (PIN, LNGPIO_PIN_DIRECTION_IN))
+    return (1);
+
+  if (-1 == lngpio_set_edge (PIN, LNGPIO_PIN_EDGE_BOTH))
+    return (1);
+
+  monitor = lngpio_pin_monitor_create (PIN, status_changed);
+  if (NULL == monitor)
+    return (1);
+
+  while (1) {
+    usleep (100000);
+  }
+
+  if (-1 == lngpio_pin_monitor_stop (monitor))
+    return (1);
+
+  if (-1 == lngpio_unexport (PIN))
+    return (1);
+
+  return (0);
+}