Initial checkin of empty MCP9808 driver

include/mgos_mcp9808.h

@@ -0,0 +1,54 @@
+#pragma once
+
+#include "mgos.h"
+#include "mgos_i2c.h"
+
+#define MGOS_MCP9808_READ_DELAY (2)
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct mgos_mcp9808;
+
+/* 
+ * Initialize a MCP9808 on the I2C bus `i2c` at address specified in `i2caddr`
+ * parameter (default MCP9808 is on address 0x18). The sensor will be polled for
+ * validity, upon success a new `struct mgos_mcp9808` is allocated and
+ * returned. If the device could not be found, NULL is returned.
+ */
+struct mgos_mcp9808 *mgos_mcp9808_create(struct mgos_i2c *i2c, uint8_t i2caddr);
+
+/* 
+ * Destroy the data structure associated with a MCP9808 device. The reference
+ * to the pointer of the `struct mgos_mcp9808` has to be provided, and upon
+ * successful destruction, its associated memory will be freed and the pointer
+ * set to NULL.
+ */
+void mgos_mcp9808_destroy(struct mgos_mcp9808 **sensor);
+
+/* 
+ * The sensor will be polled for its temperature and humidity data. If the poll
+ * has occured in the last `MGOS_MCP9808_READ_DELAY` seconds, the cached data is
+ * used (so as not to repeatedly poll the bus upon subsequent calls).
+ */
+bool mgos_mcp9808_read(struct mgos_mcp9808 *sensor);
+
+/*
+ * The sensor will be polled for its temperature and humidity data. If the poll
+ * has occured in the last `MGOS_MCP9808_READ_DELAY` seconds, the cached data is
+ * used (so as not to repeatedly poll the bus upon subsequent calls).
+ *
+ * The return value is the temperature of the sensor in Celsius, or NAN if no
+ * data was found.
+ */
+float mgos_mcp9808_getTemperature(struct mgos_mcp9808 *sensor);
+
+/*
+ * Initialization function for MGOS -- currently a noop.
+ */
+bool mgos_mcp9808_i2c_init(void);
+
+#ifdef __cplusplus
+}
+#endif

src/main.c

@@ -3,10 +3,11 @@
 #include "mgos_sht31.h"
 #include "mgos_si7021.h"
 #include "mgos_htu21df.h"
+#include "mgos_mcp9808.h"
 #include <fcntl.h>
 #include <sys/ioctl.h>
 
-#define I2CBUSNR 7
+#define I2CBUSNR 5
 
 void i2c_scanner(struct mgos_i2c *i2c) {
   int i;
@@ -76,11 +77,23 @@ bool do_htu21df(struct mgos_htu21df *sensor) {
   return true;
 }
 
+bool do_mcp9808(struct mgos_mcp9808 *sensor) {
+  float temp;
+
+  if (!sensor) return false;
+
+  temp=mgos_mcp9808_getTemperature(sensor);
+  LOG(LL_INFO, ("temperature=%.2fC", temp));
+
+  return true;
+}
+
 int main() {
   struct mgos_i2c *i2c;
   struct mgos_si7021 *si7021;
   struct mgos_sht31 *sht31;
   struct mgos_htu21df *htu21df;
+  struct mgos_mcp9808 *mcp9808;
 
   if (!mgos_i2c_open(I2CBUSNR)) {
     LOG(LL_ERROR, ("Cannot open I2C bus %u", I2CBUSNR));
@@ -102,6 +115,9 @@ int main() {
   if (!(htu21df = mgos_htu21df_create(i2c, 0x40))) 
     LOG(LL_ERROR, ("Cannot create HTU21DF device"));
 
+  if (!(mcp9808 = mgos_mcp9808_create(i2c, 0x18))) 
+    LOG(LL_ERROR, ("Cannot create MCP9808 device"));
+
   for (;;) {
     do_sht31(sht31);
     do_si7021(si7021);
@@ -112,6 +128,7 @@ int main() {
   mgos_sht31_destroy(&sht31);
   mgos_si7021_destroy(&si7021);
   mgos_htu21df_destroy(&htu21df);
+  mgos_mcp9808_destroy(&mcp9808);
 
   return 0;
 }

src/mgos_mcp9808.c

@@ -0,0 +1,82 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "mgos.h"
+#include "mgos_mcp9808_internal.h"
+#include "mgos_i2c.h"
+
+// Datasheet:
+// https://cdn-shop.adafruit.com/datasheets/MCP9808.pdf
+
+// Private functions follow
+// Private functions end
+
+// Public functions follow
+struct mgos_mcp9808 *mgos_mcp9808_create(struct mgos_i2c *i2c, uint8_t i2caddr) {
+  struct mgos_mcp9808 *sensor;
+
+  if (!i2c) return NULL;
+
+  sensor=calloc(1, sizeof(struct mgos_mcp9808));
+  if (!sensor) return NULL;
+  sensor->i2caddr=i2caddr;
+  sensor->i2c=i2c;
+  sensor->last_read_time=0;
+
+  // Check for the right chip.
+  if (false) {
+    LOG(LL_INFO, ("MCP9808 created at I2C 0x%02x", i2caddr));
+    return sensor;
+  }
+
+  LOG(LL_ERROR, ("Failed to create MCP9808 at I2C 0x%02x", i2caddr));
+  free(sensor);
+  return NULL;
+}
+
+void mgos_mcp9808_destroy(struct mgos_mcp9808 **sensor) {
+  if (!*sensor) return;
+  free (*sensor);
+  *sensor=NULL;
+  return;
+}
+
+bool mgos_mcp9808_read(struct mgos_mcp9808 *sensor) {
+  double now = mg_time();
+
+  if (!sensor || !sensor->i2c)
+    return false;
+
+  if (now - sensor->last_read_time < MGOS_MCP9808_READ_DELAY) {
+    return true;
+  }
+  // Read out sensor data here 
+  //
+  LOG(LL_DEBUG, ("temperature=%.2fC", sensor->temperature));
+  sensor->last_read_time=now;
+  return true;
+}
+
+float mgos_mcp9808_getTemperature(struct mgos_mcp9808 *sensor) {
+  if (!mgos_mcp9808_read(sensor)) return NAN;
+
+  return sensor->temperature;
+}
+
+bool mgos_mcp9808_i2c_init(void) {
+  return true;
+}
+// Public functions end

src/mgos_mcp9808_internal.h

@@ -0,0 +1,36 @@
+#pragma once
+
+#include "mgos.h"
+#include "mgos_i2c.h"
+#include "mgos_mcp9808.h"
+#include <math.h>
+
+#define MGOS_MCP9808_DEFAULT_I2CADDR       (0x18)
+
+#define MGOS_MCP9808_MEAS_HIGHREP_STRETCH  (0x2C06)
+#define MGOS_MCP9808_MEAS_MEDREP_STRETCH   (0x2C0D)
+#define MGOS_MCP9808_MEAS_LOWREP_STRETCH   (0x2C10)
+#define MGOS_MCP9808_MEAS_HIGHREP          (0x2400)
+#define MGOS_MCP9808_MEAS_MEDREP           (0x240B)
+#define MGOS_MCP9808_MEAS_LOWREP           (0x2416)
+#define MGOS_MCP9808_READSTATUS            (0xF32D)
+#define MGOS_MCP9808_CLEARSTATUS           (0x3041)
+#define MGOS_MCP9808_SOFTRESET             (0x30A2)
+#define MGOS_MCP9808_HEATEREN              (0x306D)
+#define MGOS_MCP9808_HEATERDIS             (0x3066)
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct mgos_mcp9808 {
+  struct mgos_i2c *i2c;
+  uint8_t i2caddr;
+  double last_read_time;
+
+  float temperature;
+};
+
+#ifdef __cplusplus
+}
+#endif