BME680 BSEC: support state (de)serialization across application restarts

src/app/bme680-bsec/main.cc

@@ -3,6 +3,15 @@
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
+
+#include "config.h"
+#ifdef CONFIG_driver_bme680_bsec_save_state
+#define STRINGIFY(x) #x
+#define TOSTRING(x) STRINGIFY(x)
+#define BSEC_STATE_PATH TOSTRING(CONFIG_driver_bme680_bsec_state_path)
+#include <stdio.h>
+#endif
+
 #include "arch.h"
 #include "driver/gpio.h"
 #include "driver/stdout.h"
@@ -20,10 +29,18 @@
 
 const char* accuracy[] = {"(unreliable)", "(calibration required)", "(auto-trim in progress)", ""};
 
+#ifdef CONFIG_driver_bme680_bsec_save_state
+// For (de)serialization of library state across application restarts
+uint8_t serialized_state[BSEC_MAX_STATE_BLOB_SIZE];
+uint8_t work_buffer[BSEC_MAX_STATE_BLOB_SIZE];
+#endif
+
 void loop(void)
 {
 	static bsec_bme_settings_t sensor_settings;
 
+	static uint16_t iteration = 0;
+
 	struct bme680_field_data data;
 	bsec_input_t bsec_inputs[BSEC_MAX_PHYSICAL_SENSOR];
 	bsec_output_t bsec_outputs[BSEC_NUMBER_OUTPUTS];
@@ -177,6 +194,32 @@ void loop(void)
 			kout << endl;
 		}
 	}
+
+#ifdef CONFIG_driver_bme680_bsec_save_state
+	if (++iteration == 600) {
+		uint32_t  serialized_state_size;
+		status = bsec_get_state(0, serialized_state, BSEC_MAX_STATE_BLOB_SIZE, work_buffer, BSEC_MAX_STATE_BLOB_SIZE, &serialized_state_size);
+		if (status < 0) {
+			kout << "bsec_get_state error: " << status << endl;
+			return;
+		}
+		if (status > 0) {
+			kout << "bsec_get_state warning: " << status << endl;
+		}
+		FILE *f = fopen(BSEC_STATE_PATH, "w");
+		if (f == NULL) {
+			perror("fopen");
+			return;
+		}
+		if (fwrite(serialized_state, sizeof(uint8_t), serialized_state_size, f) < serialized_state_size) {
+			perror("fwrite");
+		}
+		if (fclose(f) == EOF) {
+			perror("fclose");
+		}
+		iteration = 0;
+	}
+#endif
 }
 
 int main(void)
@@ -215,6 +258,28 @@ int main(void)
 	}
 	kout << "BSEC init OK" << endl;
 
+#ifdef CONFIG_driver_bme680_bsec_save_state
+	FILE *f = fopen(BSEC_STATE_PATH, "r");
+	if (f != NULL) {
+		size_t serialized_state_size = fread(serialized_state, BSEC_MAX_STATE_BLOB_SIZE, sizeof(uint8_t), f);
+		if (serialized_state_size > 0) {
+			bsec_status = bsec_set_state(serialized_state, BSEC_MAX_STATE_BLOB_SIZE, work_buffer, BSEC_MAX_STATE_BLOB_SIZE);
+			if (bsec_status < 0) {
+				kout << "bsec_set_state error: " << bsec_status << endl;
+			}
+			if (bsec_status > 0) {
+				kout << "bsec_set_state warning: " << bsec_status << endl;
+			}
+		}
+		if (fclose(f) == EOF) {
+			perror("fclose");
+		}
+	} else {
+		// file doesn't exist. that's harmless.
+		perror("fopen");
+	}
+#endif
+
 	/*
 	 * Output configuration. The BME680 BSEC library supports several virtual
 	 * sensors such as raw temperature, compensated temperature, or IAQ. Each

src/driver/Kconfig

@@ -37,11 +37,10 @@ depends on meta_driver_i2c && !driver_bme280
 
 config driver_bme680_bsec
 bool "with BSEC (proprietary library for IAQ calculation)"
-depends on driver_bme680 && (arch_msp430fr5994lp || arch_posix)
+depends on driver_bme680 && arch_posix
 # incompatible with avr-gcc 5:
 # /usr/lib/gcc/avr/5.4.0/../../../avr/bin/ld: avr:6 architecture of input file `...' is incompatible with avr:5 output
 
-
 config driver_bme680_bsec_path
 string "BSEC library path"
 default "bme680-bsec-lite" if arch_arduino_nano
@@ -49,6 +48,15 @@ default "bme680-bsec" if arch_msp430fr5994lp
 default "bme680-bsec-armv6" if arch_posix
 depends on driver_bme680_bsec
 
+config driver_bme680_bsec_save_state
+bool "Save and Load library state (requires stdio)"
+depends on driver_bme680_bsec
+
+config driver_bme680_bsec_state_path
+string "BSEC state path"
+default "/boot/bme680-bsec.state" if arch_posix
+depends on driver_bme680_bsec_save_state
+
 config driver_ccs811
 bool "CCS811 VOC Sensor"
 depends on meta_driver_i2c