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Add finished MPL115 barometer

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This commit is contained in:
Pim van Pelt
2018-04-21 17:47:56 +02:00
parent 9d9cd1d00a
commit d142cb37d3
2 changed files with 25 additions and 10 deletions
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2
src/main.c
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@ -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 (;;) {

33
src/mgos_barometer_mpl115.c
View File

@ -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;
}