Added battery level in lora stack and nano libc profile

README.md

@@ -15,7 +15,7 @@ mbed target NUCLEO_L073RZ
 mbed config -G GCC_ARM_PATH /opt/gcc-arm-none-eabi-7-2017-q4-major/bin
 cp mbed_app.json.sample mbed_app.json
 # modify lora.device-eui, lora.application-eui and lora.application-key in mbed_app.json
-mbed compile --profile minimal-printf/profiles/release.json
+mbed compile --profile profiles/release.json
 ```
 
 Then you can use stm32flash or - may be better - a stlink interface to copy the generated .bin file onto the RAK811.

main.cpp

@@ -37,6 +37,23 @@ static CayenneLPP cayenne(51);
 
 #if MBED_CONF_APP_BATTERY_ENABLED
 AnalogIn bat(MBED_CONF_APP_BATTERY_ADC);
+AnalogIn vrefint(ADC_VREF);
+
+static float battery_voltage() {
+    float vbat = bat.read();
+    double vdd = (1.224f) / vrefint.read();
+
+    return vbat * MBED_CONF_APP_BATTERY_RATIO * vdd;
+}
+
+static uint8_t battery_level() {
+    float vbat = battery_voltage();
+
+    double ratio = 253.0f / (4.2f - 3.3f);
+    int value = ratio * (vbat - 3.4f) + 1.0f;
+
+    return value < 1 ? 1 : (value > 254 ? 254 : value);
+}
 #endif
 
 #if MBED_CONF_APP_DHT_ENABLED
@@ -47,10 +64,7 @@ DHT dht(MBED_CONF_APP_DHT_DATA, MBED_CONF_APP_DHT_TYPE);
 HX711 loadcell(MBED_CONF_APP_HX711_CLK, MBED_CONF_APP_HX711_DATA);
 #endif
 
-//DigitalOut led(LED1, 1);
-
 int main(void) {
-
     lorawan_status_t retcode;
 
 #if MBED_CONF_APP_HX711_ENABLED
@@ -68,6 +82,9 @@ int main(void) {
     debug("\r\n Mbed LoRaWANStack initialized \r\n");
 
     callbacks.events = mbed::callback(lora_event_handler);
+#if MBED_CONF_APP_BATTERY_ENABLED
+    callbacks.battery_level = mbed::callback(battery_level);
+#endif
     lorawan.add_app_callbacks(&callbacks);
 
     // Set number of retries in case of CONFIRMED messages
@@ -86,8 +103,6 @@ int main(void) {
 
     debug("\r\n Adaptive data  rate (ADR) - Enabled \r\n");
 
-    //led = 0;
-
     retcode = lorawan.connect();
 
     if(retcode == LORAWAN_STATUS_OK || retcode == LORAWAN_STATUS_CONNECT_IN_PROGRESS) {
@@ -110,10 +125,8 @@ int main(void) {
 static void send_message() {
     int16_t retcode;
 
-#if MBED_CONF_APP_BATTERY_ENABLED
+#if MBED_CONF_APP_BATTERY_ENABLED && MBED_CONF_APP_BATTERY_IN_LPP
-    float vbat = bat.read();
+    cayenne.addAnalogInput(1, battery_voltage());
-    vbat = vbat * MBED_CONF_APP_BATTERY_RATIO * 3.3f;
-    cayenne.addAnalogInput(1, vbat);
 #endif
 
 #if MBED_CONF_APP_DHT_ENABLED
@@ -179,7 +192,6 @@ static void receive_message() {
 static void lora_event_handler(lorawan_event_t event) {
     switch(event) {
         case CONNECTED:
-            //led = 1;
             debug("\r\n Connection - Successful \r\n");
             if(MBED_CONF_LORA_DUTY_CYCLE_ON) {
                 send_message();

mbed_app.json.sample

@@ -25,6 +25,7 @@
         "lora-pwr-amp-ctl":    { "value": "NC" },
         "lora-tcxo":           { "value": "NC" },
         "battery-enabled":     { "value": "false" },
+        "battery-in-lpp":      { "value": "false" },
         "battery-adc":         { "value": "NC" },
         "battery-ratio":       { "value": "2.0f" },
         "dht-enabled":         { "value": "false" },
@@ -280,6 +281,7 @@
             "lora-pwr-amp-ctl":    "NC",
             "lora-tcxo":           "NC",
             "battery-enabled":     true,
+            "battery-in-lpp":      true,
             "battery-adc":         "A1",
             "battery-ratio":       "2.0f",
             "dht-enabled":         true,

profiles/release.json

@@ -12,7 +12,7 @@
         "ld": ["-Wl,--gc-sections", "-Wl,--wrap,main", "-Wl,--wrap,_malloc_r",
                "-Wl,--wrap,_free_r", "-Wl,--wrap,_realloc_r", "-Wl,--wrap,_memalign_r",
                "-Wl,--wrap,_calloc_r", "-Wl,--wrap,exit", "-Wl,--wrap,atexit",
-               "-Wl,-n", "--specs=nano.specs"]
+               "-Wl,-n", "--specs=nano.specs", "-u _printf_float"]
     },
     "ARMC6": {
         "common": ["-c", "--target=arm-arm-none-eabi", "-mthumb", "-Oz",