STM32F103C8Tx medium-density LQFP48

Pin mapping: see datasheet Table 5

## GPIO inputs

Analog RX AGC measurement (S-Meter)
 * PA5

Digital buttons
 * BTN0 PB1
 * BTN1 PB0
 * BTN2 PB12
 * BTN3 PB13

Digital rotary encoder
 * ENC_A   PA6 (TIM3 CH1)
 * ENC_B   PA7 (TIM3 CH2)
 * ENC_BTN PC15 (limited current)

CW paddle
 * CW_TIP  PB8
 * CW_RING PB9

Microphone switches
 * SW1 PA3 ADC12_IN3
 * SW2 PA4 ADC12_IN4

## GPIO outputs

 * SEQ0n PB3
 * SEQ1 PB4
 * SEQ2 PB5
 * CW_KEYn PA15
 * MUTE_SPKR PA2
 * MUTE_MICn PA1

## I2C1 for Si5351A-B-GT

 * SCL  PB6 default alternate function
 * SDA  PB7 default alternate function

## I2C2 for Display, on address 0100<A2><A1><A0> depending on the solder bridges.

 * SCL   PB10   default alternate function
 * SDA   PB11   default alternate function