STM32F103C8Tx medium-density LQFP48

Pin mapping: see datasheet Table 5

## GPIO inputs

Analog RX AGC measurement
 * S-Meter PA5

Digital buttons, all with external pullup
 * BTN A PB1
 * BTN B PB0
 * BTN C PB12
 * BTN D PB13

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

CW paddle
 * CW_TIP  PB8
 * CW_RING PB9

CW output
 * Sidetone PA8 (TIM1 CH1)

Microphone switches
 * MIC_PTT PA3 ADC12_IN3 (floating)
 * VOX_PTTn PA0 ADC12_IN0 (needs internal pullup)

## GPIO outputs

 * EN_PA PB3
 * EN_RX PB4
 * EN_TX PB5
 * CW_KEYn PA15
 * MUTE_SPKR PA2
 * MUTE_MICn PA1
 * STATUSn PB14

## Reserved for future use
To XTAL filter board
 * GPIO_XTAL PA4 ADC12_IN4

J33 Header
* PB15
* PA9 USART1_TX
* PA10 USART1_RX

## 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

## Timers
TIM1 is an advanced control timer, TIM2,3,4 are general purpose

 * TIM1 CW Sidetone PWM output
 * TIM2 Clock timer
 * TIM3 QEI decoder
 * TIM4