Add picocalc stm32 i2c keyboard code

Code/picocalc_keyboard/battery.ino

@@ -0,0 +1,74 @@
+#include "battery.h"
+
+
+void indicator_led_on(){
+    digitalWrite(PC13, LOW);
+}
+
+void indicator_led_off(){
+    digitalWrite(PC13, HIGH);
+}
+
+void flash_one_time(int ts,int restore_status) {
+    for(int i=0;i<ts;i++) {
+      indicator_led_on();
+      delay(400);
+      indicator_led_off();
+      delay(200);
+    }
+    digitalWrite(PC13,restore_status);
+}
+
+void show_bat_segs(){
+  if(!PMU.isBatteryConnect()) return;
+
+  int pcnt =  PMU.getBatteryPercent();
+  int last_d201_status = digitalRead(PC13);
+  
+  if(pcnt >0 && pcnt < 33) {
+    //show one time
+    flash_one_time(1,last_d201_status);
+  }else if(pcnt >= 33 && pcnt <66){
+    //show 2 times
+     flash_one_time(2,last_d201_status);   
+  }else if(pcnt >=66 && pcnt <= 100){
+    //show 3 times
+     flash_one_time(3,last_d201_status);
+  }
+  
+  if(PMU.isCharging()){
+    start_chg();
+  }
+
+}
+
+void low_bat(){
+  if(PMU.isBatteryConnect() && !PMU.isCharging()){
+    int pcnt = PMU.getBatteryPercent();
+     if(pcnt <= LOW_BAT_VAL){
+      //This is related to the battery charging and discharging logic. If you're not sure what you're doing, please don't modify it, as it could damage the battery.
+        indicator_led_off();      
+        if(pcnt <= 1) {//This is related to the battery charging and discharging logic. If you're not sure what you're doing, please don't modify it, as it could damage the battery.
+          PMU.setChargingLedMode(XPOWERS_CHG_LED_BLINK_4HZ);
+          if(pcnt==0){//This is related to the battery charging and discharging logic. If you're not sure what you're doing, please don't modify it, as it could damage the battery.
+            PMU.shutdown();//This is related to the battery charging and discharging logic. If you're not sure what you're doing, please don't modify it, as it could damage the battery.
+          }
+        }else{
+          PMU.setChargingLedMode(XPOWERS_CHG_LED_ON);
+        }
+     }else{
+        indicator_led_on();
+        PMU.setChargingLedMode(XPOWERS_CHG_LED_OFF);
+     }
+  }
+}
+
+void start_chg(){
+  indicator_led_on();
+  PMU.setChargingLedMode(XPOWERS_CHG_LED_BLINK_1HZ);
+}
+
+void stop_chg(){
+  PMU.setChargingLedMode(XPOWERS_CHG_LED_OFF);
+  low_bat();
+}