# Blue Pill Notes

## Baseline

- Board: STM32F103C8T6 Blue Pill
- Core: Cortex-M3
- Default target: `thumbv7m-none-eabi`

## LED

- Most Blue Pill boards wire the onboard LED to `PC13`
- It is usually active-low
- `set_low()` usually turns it on
- `set_high()` usually turns it off

## RGB LED

- `PA0` = GND, drive low
- `PA1` = red
- `PA2` = green
- `PA3` = blue
- The RGB fade example uses software PWM on `PA1`, `PA2`, and `PA3`

## 5-Way Button Board

- `PB12` = GND, drive low
- `PA10` = VCC, drive high
- `PB13` = right
- `PB14` = down
- `PB15` = left
- `PA8` = center
- `PA9` = up
- Assumption: the button inputs read high when pressed
- The button examples use `PA8` as the default center button
- TODO: flip the input polarity if your module is active-low instead

## HMC5883L Module

- `PB4` = VCC, drive high
- `PB5` = GND, drive low
- `PB6` = SCL
- `PB7` = SDA
- `PB8` = DRDY

## Probe Wiring

- `SWDIO` -> `SWDIO`
- `SWCLK` -> `SWCLK`
- `GND` -> `GND`
- `3V3` -> `3V3` reference