RTC works, 5V needed

LedRing.ioc

@@ -19,11 +19,12 @@ KeepUserPlacement=false
 Mcu.CPN=STM32F103C6T6A
 Mcu.Family=STM32F1
 Mcu.IP0=DMA
-Mcu.IP1=NVIC
-Mcu.IP2=RCC
-Mcu.IP3=SYS
-Mcu.IP4=TIM2
-Mcu.IPNb=5
+Mcu.IP1=I2C1
+Mcu.IP2=NVIC
+Mcu.IP3=RCC
+Mcu.IP4=SYS
+Mcu.IP5=TIM2
+Mcu.IPNb=6
 Mcu.Name=STM32F103C(4-6)Tx
 Mcu.Package=LQFP48
 Mcu.Pin0=PC13-TAMPER-RTC
@@ -32,9 +33,11 @@ Mcu.Pin2=PD1-OSC_OUT
 Mcu.Pin3=PA0-WKUP
 Mcu.Pin4=PA13
 Mcu.Pin5=PA14
-Mcu.Pin6=VP_SYS_VS_Systick
-Mcu.Pin7=VP_TIM2_VS_ClockSourceINT
-Mcu.PinsNb=8
+Mcu.Pin6=PB6
+Mcu.Pin7=PB7
+Mcu.Pin8=VP_SYS_VS_Systick
+Mcu.Pin9=VP_TIM2_VS_ClockSourceINT
+Mcu.PinsNb=10
 Mcu.ThirdPartyNb=0
 Mcu.UserConstants=
 Mcu.UserName=STM32F103C6Tx
@@ -58,6 +61,10 @@ PA13.Mode=Serial_Wire
 PA13.Signal=SYS_JTMS-SWDIO
 PA14.Mode=Serial_Wire
 PA14.Signal=SYS_JTCK-SWCLK
+PB6.Mode=I2C
+PB6.Signal=I2C1_SCL
+PB7.Mode=I2C
+PB7.Signal=I2C1_SDA
 PC13-TAMPER-RTC.GPIOParameters=GPIO_Label
 PC13-TAMPER-RTC.GPIO_Label=LED_Green
 PC13-TAMPER-RTC.Locked=true