diff --git a/src/main.c b/src/main.c
index 6485d44..5405819 100644
--- a/src/main.c
+++ b/src/main.c
@@ -218,7 +218,7 @@ int main() {
   if (!(baro=mgos_barometer_create_i2c(i2c, 0x60, BARO_MPL115))) {
     LOG(LL_ERROR, ("Cannot create MPL115 barometer"));
   } else {
-    mgos_barometer_set_cache_ttl(baro, 5000);
+    mgos_barometer_set_cache_ttl(baro, 0);
   }
 
   for (;;) {
diff --git a/src/mgos_barometer_mpl115.c b/src/mgos_barometer_mpl115.c
index b3e1ed5..eb79140 100644
--- a/src/mgos_barometer_mpl115.c
+++ b/src/mgos_barometer_mpl115.c
@@ -1,6 +1,9 @@
 #include "mgos_barometer_mpl115.h"
 #include "mgos_i2c.h"
 
+// Datasheet:
+// https://cdn-shop.adafruit.com/datasheets/MPL115A2.pdf
+
 bool mgos_barometer_mpl115_create(struct mgos_barometer *dev) {
   struct mgos_barometer_mpl115_data *mpl115_data;
 
@@ -12,13 +15,18 @@ bool mgos_barometer_mpl115_create(struct mgos_barometer *dev) {
   mpl115_data=calloc(1, sizeof(struct mgos_barometer_mpl115_data));
   if (!mpl115_data) return false;
 
-  // TODO(pim): fix this -- math is wrong.
-  mpl115_data->a0=(float)(((uint16_t) data[0] << 8) | data[1]) / 8.0;
-  mpl115_data->b1=(float)(((uint16_t) data[2] << 8) | data[3]) / 8192.0;
-  mpl115_data->b2=(float)(((uint16_t) data[4] << 8) | data[5]) / 16384.0;
-  mpl115_data->c12=(float)((((uint16_t) (data[6] << 8) | data[7])) >> 2) / 4194304.0;
+  // TESTDATA:
+  // data[0]=0x3e; data[1]=0xce; data[2]=0xb3; data[3]=0xf9; data[4]=0xc5; data[5]=0x17; data[6]=0x33; data[7]=0xc8;
+  int16_t a0 = ((uint16_t) data[0] << 8) | data[1];
+  int16_t b1 = ((uint16_t) data[2] << 8) | data[3];
+  int16_t b2 = ((uint16_t) data[4] << 8) | data[5];
+  int16_t c12 = (((uint16_t) data[6] << 8) | data[7]) >> 2;
+
+  mpl115_data->a0=(float)a0/(1<<3);
+  mpl115_data->b1=(float)b1/(1<<13);
+  mpl115_data->b2=(float)b2/(1<<14);
+  mpl115_data->c12=(float)c12/(1<<22);
   dev->user_data=mpl115_data;
-  LOG(LL_DEBUG, ("Calibration data: a0=%.4f b1=%.4f b2=%.4f c12=%.4f", mpl115_data->a0, mpl115_data->b1, mpl115_data->b2, mpl115_data->c12));
 
   dev->has_barometer=true;
   dev->has_thermometer=true;
@@ -36,7 +44,7 @@ bool mgos_barometer_mpl115_destroy(struct mgos_barometer *dev) {
 
 bool mgos_barometer_mpl115_read(struct mgos_barometer *dev) {
   struct mgos_barometer_mpl115_data *mpl115_data;
-  uint16_t Padc, Tadc;
+  int16_t Padc, Tadc;
   float Pcomp;
 
   if (!dev) return false;
@@ -50,14 +58,21 @@ bool mgos_barometer_mpl115_read(struct mgos_barometer *dev) {
   uint8_t data[4];
   if (!mgos_i2c_read_reg_n(dev->i2c, dev->i2caddr, MPL115_REG_PRESSURE, 4, data))
     return false;
+  // TESTDATA:
+  // data[0]=0x66; data[1]=0x80; data[2]=0x7e; data[3]=0xc0;
   Padc=(((uint16_t) data[0] << 8) | data[1]) >> 6;
   Tadc=(((uint16_t) data[2] << 8) | data[3]) >> 6;
 
-  Pcomp= mpl115_data->a0 + (mpl115_data->b1 + mpl115_data->c12 * Tadc ) * Padc + mpl115_data->b2 * Tadc;
+  Pcomp=mpl115_data->a0 + (mpl115_data->b1 + mpl115_data->c12 * Tadc ) * Padc + mpl115_data->b2 * Tadc;
 
-  dev->pressure= 1000*Pcomp*(65.0/1023) + 50.0;        // Pascals
+  dev->pressure=(Pcomp*(65.0/1023) + 50.0)*1000;        // Pascals
   dev->temperature=((float) Tadc - 498.0F) / -5.35F +25.0F;           // Celsius
 
+  /* TESTDATA (in mpl115_data and Padc/Tadc) yields:
+   * pressure=96587.33
+   * temperature=23.32
+   */
+
   return true;
 }