Initial Checkin.

Only DHT (AM3202) supported at this time.

.gitignore

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+build/
+deps/

README.md

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+# Prometheus Sensors
+
+This is a library that implements a set of sensor types, reading their values
+periodically and exposing them to Prometheus using the `prometheus-metrics`
+library.
+
+## Supported Sensors
+
+### DHT 
+
+This is using `dht` library; each sensor reading takes approximately 32ms (28ms
+if there is no sensor on the GPIO in). They are placed on timers so as to
+minimize pre-emption of the main application. DHT sensors are polled in order
+based on `sensors.dht_gpio` pins and with a period of `sensors.dht_period`
+which defaults to 3 seconds.

include/mgos_prometheus_sensors.h

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+#ifndef __MGOS_PROMETHEUS_SENSORS_H
+#define __MGOS_PROMETHEUS_SENSORS_H
+
+#include "mgos.h"
+#include "mgos_gpio.h"
+
+#endif // __MGOS_PROMETHEUS_SENSORS_H

mos.yml

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+author: Pim van Pelt <pim@ipng.nl>
+description: Library that interfaces sensors to Prometheus Metrics
+type: lib
+version: 1.0
+platforms: [esp32, esp8266]
+
+tags:
+  - c
+
+# List of files / directories with C sources. No slashes at the end of dir names.
+sources:
+  - src
+
+includes:
+  - include
+
+config_schema:
+  - ["sensors", "o", {title: "Sensors settings"}]
+  - ["sensors.dht_gpio", "s", "13,12,14", {title: "Comma Separated list of GPIO pins to enable DHT22/AM2302 sensors on"}]
+  - ["sensors.dht_period", "i", 3, {title: "Sample period in seconds for DHT sensors"}]
+  - ["prometheus.pushgateway", "prometheus.example.net:9091"]
+
+
+# List of libraries used by this app, in order of initialisation
+libs:
+  - origin: https://github.com/mongoose-os-libs/dht
+  - origin: https://github.com/mongoose-os-libs/prometheus-metrics
+
+# Used by the mos tool to catch mos binaries incompatible with this file format
+manifest_version: 2017-05-18

src/dht.c

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+#include "mgos.h"
+
+#ifdef MGOS_HAVE_DHT
+#include "main.h"
+#include "mgos_dht.h"
+#include "mgos_config.h"
+#include "mgos_prometheus_metrics.h"
+#include "mqtt.h"
+
+#define MAX_DHT 8
+
+struct dht_sensor {
+  struct mgos_dht *dht;
+  float temp;
+  float humidity;
+  uint8_t gpio;
+  uint8_t idx;
+};
+
+static struct dht_sensor *s_dht_sensor[MAX_DHT];
+static int s_num_dht = 0;
+
+static void print_chunk(struct mg_connection *nc, char *name, char *fmt, ...) {
+  char chunk[500];
+  int chunklen=0;
+  va_list ap;
+
+  snprintf(chunk, sizeof(chunk), "%s%s", name, fmt[0]=='{' ? "" : " ");
+  va_start(ap, fmt);
+  vsnprintf(chunk+strlen(chunk), sizeof(chunk)-strlen(chunk), fmt, ap);
+  va_end(ap);
+  strncat(chunk, "\n", sizeof(chunk));
+  chunklen=strlen(chunk);
+  LOG(LL_DEBUG, ("Chunk '%s' with length %d", chunk, chunklen));
+  mg_printf(nc, "%X\r\n%s\r\n", chunklen, chunk);
+
+}
+
+static void dht_prometheus_metrics(struct mg_connection *nc, void *user_data) {
+  int i;
+
+  // BUG -- repeated HELP and TYPE makes Prometheus parser bork :(
+  mgos_prometheus_metrics_printf(nc, GAUGE,
+    "temperature", "Temperature in celcius",
+    "{sensor=\"0\",type=\"DHT\"} %f", s_dht_sensor[0]->temp);
+  mgos_prometheus_metrics_printf(nc, GAUGE,
+    "humidity", "Relative humidity percentage",
+    "{sensor=\"0\",type=\"DHT\"} %f", s_dht_sensor[0]->humidity);
+
+  for (i=1; i<s_num_dht; i++) {
+    print_chunk(nc, "temperature", "{sensor=\"%d\",type=\"DHT\"} %f", i, s_dht_sensor[i]->temp);
+    print_chunk(nc, "humidity", "{sensor=\"%d\",type=\"DHT\"} %f", i, s_dht_sensor[i]->humidity);
+  }
+
+  (void) user_data;
+}
+
+static void dht_timer_cb(void *user_data) {
+  struct dht_sensor *dht_sensor = (struct dht_sensor *)user_data;
+  double start;
+  uint32_t usecs=0;
+
+  if (!dht_sensor) return;
+
+  start=mgos_uptime();
+  dht_sensor->temp = mgos_dht_get_temp(dht_sensor->dht);
+  dht_sensor->humidity = mgos_dht_get_humidity(dht_sensor->dht);
+  usecs=1000000*(mgos_uptime()-start);
+  LOG(LL_DEBUG, ("DHT sensor=%u gpio=%u temp=%.2fC humidity=%.0f%% usecs=%u", dht_sensor->idx, dht_sensor->gpio, dht_sensor->temp, dht_sensor->humidity, usecs));
+}
+
+static bool dht_sensor_create(int pin, enum dht_type type) {
+  struct dht_sensor *dht_sensor = calloc(1, sizeof(struct dht_sensor));
+  if (s_num_dht == MAX_DHT) {
+    LOG(LL_ERROR, ("No more sensor slots available (%d added)", MAX_DHT));
+    free(dht_sensor);
+    return false;
+  }
+
+  dht_sensor->dht=mgos_dht_create(pin, type);
+  if (!dht_sensor->dht) {
+    LOG(LL_ERROR, ("Could not create DHT sensor on pin %d", pin));
+    free(dht_sensor);
+    return false;
+  }
+  dht_sensor->gpio=pin;
+  dht_sensor->idx=s_num_dht;
+  s_dht_sensor[dht_sensor->idx] = dht_sensor;
+  s_num_dht++;
+  mgos_set_timer(mgos_sys_config_get_sensors_dht_period()*1000, true, dht_timer_cb, (void*)dht_sensor);
+  return true;
+}
+
+void dht_init() {
+  char *tok;
+
+  memset(s_dht_sensor, 0, sizeof (struct mgos_dht_sensor *) * MAX_DHT);
+  tok = strtok((char *)mgos_sys_config_get_sensors_dht_gpio(), ", ");
+  while (tok) {
+    int gpio;
+    gpio = atoi(tok);
+    tok=strtok(NULL, ", ");
+    dht_sensor_create(gpio, AM2302);
+    mgos_msleep(250);
+  }
+
+  if (s_num_dht>0)
+    mgos_prometheus_metrics_add_handler(dht_prometheus_metrics, NULL);
+}
+
+#else
+void dht_init() {
+  LOG(LL_ERROR, ("DHT disabled, include library in mos.yml to enable"));
+}
+#endif

src/mgos_prometheus_sensors.c

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+#include "mgos_config.h"
+#include "mgos_prometheus_sensors.h"
+
+void dht_init();
+
+bool mgos_prometheus_sensors_init(void) {
+  dht_init();
+  return true;
+}