#include #include #include "watch.h" #include "bme280.h" typedef enum ApplicationMode { MODE_TEMPERATURE = 0, MODE_HUMIDITY, MODE_OFF, } ApplicationMode; typedef struct ApplicationState { ApplicationMode mode; bool light_on; uint16_t dig_T1; int16_t dig_T2; int16_t dig_T3; uint8_t dig_H1; int16_t dig_H2; uint8_t dig_H3; int16_t dig_H4; int16_t dig_H5; int8_t dig_H6; } ApplicationState; ApplicationState application_state; void cb_mode_pressed(); void cb_tick(); float read_temperature(int32_t *p_t_fine); float read_humidity(int32_t t_fine); /** * @brief Zeroes out the application state struct. */ void app_init() { memset(&application_state, 0, sizeof(application_state)); } /** * @todo stash the BME280's calibration values in backup memory so we don't have to ask again */ void app_wake_from_deep_sleep() { } /** * Enables the MODE button, the display and the sensor, and grabs calibration data. */ void app_setup() { watch_enable_buttons(); watch_register_button_callback(BTN_MODE, cb_mode_pressed); // pin A0 powers the sensor on this board. watch_enable_digital_output(A0); watch_set_pin_level(A0, true); delay_ms(10); watch_enable_i2c(); watch_i2c_write8(BME280_ADDRESS, BME280_REGISTER_SOFTRESET, BME280_SOFT_RESET_CODE); delay_ms(10); application_state.dig_T1 = watch_i2c_read16(BME280_ADDRESS, BME280_REGISTER_DIG_T1); application_state.dig_T2 = (int16_t)watch_i2c_read16(BME280_ADDRESS, BME280_REGISTER_DIG_T2); application_state.dig_T3 = (int16_t)watch_i2c_read16(BME280_ADDRESS, BME280_REGISTER_DIG_T3); application_state.dig_H1 = watch_i2c_read8(BME280_ADDRESS, BME280_REGISTER_DIG_H1); application_state.dig_H2 = (int16_t)watch_i2c_read16(BME280_ADDRESS, BME280_REGISTER_DIG_H2); application_state.dig_H3 = watch_i2c_read8(BME280_ADDRESS, BME280_REGISTER_DIG_H3); application_state.dig_H4 = ((int8_t)watch_i2c_read8(BME280_ADDRESS, BME280_REGISTER_DIG_H4) << 4) | (watch_i2c_read8(BME280_ADDRESS, BME280_REGISTER_DIG_H4 + 1) & 0xF); application_state.dig_H5 = ((int8_t)watch_i2c_read8(BME280_ADDRESS, BME280_REGISTER_DIG_H5 + 1) << 4) | (watch_i2c_read8(BME280_ADDRESS, BME280_REGISTER_DIG_H5) >> 4); application_state.dig_H6 = (int8_t)watch_i2c_read8(BME280_ADDRESS, BME280_REGISTER_DIG_H6); watch_i2c_write8(BME280_ADDRESS, BME280_REGISTER_CONTROL_HUMID, BME280_CONTROL_HUMID_SAMPLING_X16); watch_i2c_write8(BME280_ADDRESS, BME280_REGISTER_CONTROL, BME280_CONTROL_TEMPERATURE_SAMPLING_X16 | BME280_CONTROL_PRESSURE_SAMPLING_NONE | BME280_CONTROL_MODE_FORCED); watch_enable_display(); watch_register_tick_callback(cb_tick); } /** * Nothing to do here. */ void app_prepare_for_sleep() { } /** * @todo restore the BME280's calibration values from backup memory */ void app_wake_from_sleep() { } /** * Displays the temperature and humidity on screen, or a string indicating no measurements are being taken. */ bool app_loop() { int32_t t_fine; float temperature; float humidity; char buf[11] = {0}; switch (application_state.mode) { case MODE_TEMPERATURE: // take one reading watch_i2c_write8(BME280_ADDRESS, BME280_REGISTER_CONTROL, BME280_CONTROL_TEMPERATURE_SAMPLING_X16 | BME280_CONTROL_MODE_FORCED); // wait for reading to finish while(watch_i2c_read8(BME280_ADDRESS, BME280_REGISTER_STATUS) & BME280_STATUS_UPDATING_MASK); temperature = read_temperature(NULL); sprintf(buf, "TE %4.1f#C", temperature); watch_display_string(buf, 0); watch_clear_pixel(1, 16); break; case MODE_HUMIDITY: // take one reading watch_i2c_write8(BME280_ADDRESS, BME280_REGISTER_CONTROL, BME280_CONTROL_TEMPERATURE_SAMPLING_X16 | BME280_CONTROL_MODE_FORCED); // wait for reading to finish while(watch_i2c_read8(BME280_ADDRESS, BME280_REGISTER_STATUS) & BME280_STATUS_UPDATING_MASK); temperature = read_temperature(&t_fine); humidity = read_humidity(t_fine); sprintf(buf, "HU rH %3d", (int)humidity); watch_display_string(buf, 0); watch_set_pixel(1, 16); break; case MODE_OFF: watch_display_string(" Sleep ", 0); watch_clear_pixel(1, 16); } return true; } /** * Reads the temperature from the BME280 * @param p_t_fine - an optional pointer to an int32_t; if provided, the t_fine measurement * (required for humidity calculation) will be returned by reference. * Pass in NULL if you do not care about this value. * @return a float indicating the temperature in degrees celsius. */ float read_temperature(int32_t *p_t_fine) { // read24 reads the bytes into a uint32 which works for little-endian values (MSB is 0) uint32_t raw_data = watch_i2c_read24(BME280_ADDRESS, BME280_REGISTER_TEMP_DATA) >> 8; // alas the sensor's register layout is big-endian-ish, with a nibble of zeroes at the end of the LSB. // this line shuffles everything back into place (swaps LSB and MSB and shifts the zeroes off the end) int32_t adc_value = (((raw_data >> 16) | (raw_data & 0xFF00) | (raw_data << 16)) & 0xFFFFFF) >> 4; // this bit is cribbed from Adafruit's BME280 driver. support their open source efforts by buying some stuff! int32_t var1 = ((((adc_value >> 3) - ((int32_t)application_state.dig_T1 << 1))) * ((int32_t)application_state.dig_T2)) >> 11; int32_t var2 = (((((adc_value >> 4) - ((int32_t)application_state.dig_T1)) * ((adc_value >> 4) - ((int32_t)application_state.dig_T1))) >> 12) * ((int32_t)application_state.dig_T3)) >> 14; int32_t t_fine = var1 + var2; // if we got a pointer to a t_fine, return it by reference (for humidity calculation). if (p_t_fine != NULL) *p_t_fine = t_fine; return ((t_fine * 5 + 128) >> 8) / 100.0; } /** * Reads the humidity from the BME280 * @param t_fine - the t_fine measurement from a call to read_temperature * @return a float indicating the relative humidity as a percentage from 0-100. * @todo the returned value is glitchy, need to fix. */ float read_humidity(int32_t t_fine) { int32_t adc_value = watch_i2c_read16(BME280_ADDRESS, BME280_REGISTER_HUMID_DATA); // the sensor returns this as big-endian, so swap the bytes. adc_value = (adc_value >> 8) | (adc_value << 8); // again, cribbed from Adafruit's BME280 driver. they sell a great breakout board for this sensor! int32_t v_x1_u32r = v_x1_u32r = (t_fine - ((int32_t)76800)); v_x1_u32r = (((((adc_value << 14) - (((int32_t)application_state.dig_H4) << 20) - (((int32_t)application_state.dig_H5) * v_x1_u32r)) + ((int32_t)16384)) >> 15) * (((((((v_x1_u32r * ((int32_t)application_state.dig_H6)) >> 10) * (((v_x1_u32r * ((int32_t)application_state.dig_H3)) >> 11) + ((int32_t)32768))) >> 10) + ((int32_t)2097152)) * ((int32_t)application_state.dig_H2) + 8192) >> 14)); v_x1_u32r = (v_x1_u32r - (((((v_x1_u32r >> 15) * (v_x1_u32r >> 15)) >> 7) * ((int32_t)application_state.dig_H1)) >> 4)); v_x1_u32r = (v_x1_u32r < 0) ? 0 : v_x1_u32r; v_x1_u32r = (v_x1_u32r > 419430400) ? 419430400 : v_x1_u32r; float h = (v_x1_u32r >> 12); return h / 1024.0; } void cb_mode_pressed() { application_state.mode = (application_state.mode + 1) % 3; } void cb_tick() { }