VGA demo on STM32F103 "bluepill"
The STM32F103 is a Cortex-M3 microcontroller that has neither a video controller, nor enough RAM for a framebuffer at any reasonable resolution.
This demo works around this to produce an acceptable quality 800x600 video with 64 colors to display 364x296 pixels. It uses three timers and a GPIO port.
| PIN | Description | Connect To | Output |
|---|---|---|---|
| PB08 | Red 1 | Resistor 680 Ohm | VGA red (1) |
| PB09 | Red 2 | Resistor 470 Ohm | VGA red (1) |
| PB12 | Green 1 | Resistor 680 Ohm | VGA green (2) |
| PB13 | Green 2 | Resistor 470 Ohm | VGA green (2) |
| PB14 | Blue 1 | Resistor 680 Ohm | VGA blue (3) |
| PB15 | Blue 2 | Resistor 470 Ohm | VGA blue (3) |
| PB0 | HSync | VGA HSync (13) | |
| PB6 | VSync | VGA VSync (14) | |
| PA0 | CLK | Resistor 2K2 to keyboard CLK and resistor 3K3 to GND | |
| PA1 | DATA | Resistor 2K2 to keyboard DATA and resistor 3K3 to GND | |
| G | Ground | VGA Ground (5,6,7,8,10) |
I recommend following the setup chapters from the Rust Embedded book. In particular, you need to have Rust and you need to make Rust aware of the cross compilation target we're using here:
$ rustup target add thumbv7m-none-eabiYou will also need a GNU ARM toolchain to compile the assembly language routine.
Now you should be able to compile everything by entering:
$ cargo build --releaseNote: on Windows there's currently an issue rust-embedded/cortex-m-rt#80.
- Timer TIM4 is used to generate vertical sync signal
- Timer TIM2 is used as a "shock absorber" to make the VGA stable
- Timer TIM3 is used to generate horizontal sync signal