Add MPL3115 driver; It's a bit slow (takes ~1s for DataReady to be set), should take a look

src/mgos_barometer_mpl3115.c

@@ -1,21 +1,97 @@
-#include "mgos_barometer_mpl115.h"
+#include "mgos_barometer_mpl3115.h"
 #include "mgos_i2c.h"
 
 // Datasheet:
 // https://cdn-shop.adafruit.com/datasheets/1893_datasheet.pdf
 
 bool mgos_barometer_mpl3115_detect(struct mgos_barometer *dev) {
-  return false;
+  int val;
+
+  if (!dev) {
+    return false;
+  }
+
+  if ((val = mgos_i2c_read_reg_b(dev->i2c, dev->i2caddr, MPL3115_REG_WHOAMI)) < 0) {
+    return false;
+  }
+
+  if (val != 0xC4) {
+    return false;
+  }
+
+  return true;
 }
 
 bool mgos_barometer_mpl3115_create(struct mgos_barometer *dev) {
-  return false;
-}
+  if (!dev) {
+    return false;
+  }
 
-bool mgos_barometer_mpl3115_destroy(struct mgos_barometer *dev){
-  return false;
+
+  // Reset
+  if (!mgos_i2c_write_reg_b(dev->i2c, dev->i2caddr, MPL3115_REG_CTRL1, 0x04)) {
+    return false;
+  }
+  mgos_usleep(20000);
+
+  // Set sample period to 1sec ST[3:0], period 2^ST seconds
+  if (!mgos_i2c_write_reg_b(dev->i2c, dev->i2caddr, MPL3115_REG_CTRL2, 0x00)) {
+    return false;
+  }
+
+  // Set Barometer Mode, OS[2:0], oversampling 2^OS times, continuous sampling
+  if (!mgos_i2c_write_reg_b(dev->i2c, dev->i2caddr, MPL3115_REG_CTRL1, 0x39)) {
+    return false;
+  }
+
+  // Set event flags for temp+pressure
+  if (!mgos_i2c_write_reg_b(dev->i2c, dev->i2caddr, MPL3115_REG_PT_DATA, 0x07)) {
+    return false;
+  }
+
+  dev->has_barometer   = true;
+  dev->has_thermometer = true;
+
+  return true;
 }
 
 bool mgos_barometer_mpl3115_read(struct mgos_barometer *dev) {
-  return false;
+  if (!dev) {
+    return false;
+  }
+
+  uint8_t val = 0;
+  while (!(val & 0x80)) { // Data Ready
+    if ((val = mgos_i2c_read_reg_b(dev->i2c, dev->i2caddr, MPL3115_REG_STATUS)) < 0) {
+      return false;
+    }
+    mgos_usleep(10000);
+  }
+
+  uint32_t pressure;
+  int16_t  temperature;
+  uint8_t  data[5];
+
+  if (!mgos_i2c_read_reg_n(dev->i2c, dev->i2caddr, MPL3115_REG_PRESSURE_MSB, 5, data)) {
+    return false;
+  }
+
+  pressure   = data[0];
+  pressure <<= 8;
+  pressure  |= data[1];
+  pressure <<= 8;
+  pressure  |= data[2];
+  pressure >>= 4;
+
+  temperature   = data[3];
+  temperature <<= 8;
+  temperature  |= data[4];
+  temperature >>= 4;
+  if (temperature & 0x800) {
+    temperature |= 0xF000;
+  }
+
+  dev->pressure    = pressure / 4.0;
+  dev->temperature = temperature / 16.0;
+  return true;
 }