STM32 MEDIA DRIVER TOOLKIT

This package provides a toolkit for developing applications with multimedia features using STM32 boards. It implements a VGA driver, a basic primitive drawing library, a very basic audio driver and a basic USB input device driver.

This is an adaptation of an old project that I developed in 2014.

VGA DRIVER

The driver generates a VGA signal with 256 colors RGB 2-3-3

A minimal DAC is needed to convert the 8 bit signal to the 3 channel VGA analog signals. This DAC can be easily built with only resistors. The following picture describes how to build the DAC and how to connect it to the VGA adapter:

By default, the video output on the board uses the following pins:

• B0 -> PC8
• B1 -> PC9
• B2 -> PC10
• G0 -> PC11
• G1 -> PC12
• G2 -> PC13
• R0 -> PC14
• R1 -> PC15

But in the future this will be a configurable option.

If you don't want to build the DAC, it is still possible to generate the output without it, but the color combinations will be reduced to 8. Just pick 3 pins and place a 260 Ohm resistor between each one and the corresponding color pin on the VGA connector. You can also use a single pin if you want monochrome video. There's a wide option range!

Example

Here is a basic example which demonstrates how to initialize the video driver.

#include <stdio.h>

#include <stm32f4xx.h>
#include "mdt/graphics.h"
#include "mdt/text.h"


void example(void) {

    MDT_GRAPHICS_InitTypeDef graphicsCfg = {
        .useHardwareAcceleration = true,
        .useSDRAM = false,
        .mainCtxHeight = 200,
        .mainCtxWidth = 320,
        .videoDriver = VIDEO_DRIVER_VGA,
    };

    MDT_GRAPHICS_Init(&graphicsCfg);

    while (1) {

        MDT_Clear(0x00);
        
        MDT_DrawText("Hello world!", 10, 10, 0xFF);
        
        MDT_WaitForVSync();
        
        MDT_SwapBuffers();

    }

}

Running the examples from scratch

1. Open STM32CubeIDE and create a new project: File > New > STM32 Project.

   • Click on Board Selector tab and select yours, then click next.

   • Give your project a name, use default options (C, Executable, STM32Cube) and click Finish.

   • When prompted to initialize all peripherals to default mode choose No.

     The .ioc configuration tool will open. If you go to System view only DMA, GPIO, NVIC and RCC should appear.

   • Go to Categories > System Core > SYS and set the Debug to Serial Wire.

   • Go to Categories > System > RCC and set the High Speed Clock (HSE) to Crystal/Ceramic Resonator.

   • Go to Clock configuration and choose whatever clock frequency combination you want, please note that for this project to work correctly the HCLK frequency should be a multiple of 25.175MHz, otherwise you might experience issues.

   • Go to Project Manager > Advanced Settings and set the GPIO driver to LL.

2. If you want USB support:

   • Go to Categories > Conectivity > USB_OTG_HS and set the Internal FS Phy to Host_Only.

   • Go to Categories > Middleware > USB_HOST and set the Class For HS IP option to Human Interface Host Class (HID), and in the platform Settings set the Driver_VBUS_HS to GPIO:Output and select your pin (PC4 in my case)

   • Go to Categories > System > NVIC and set Prioriy Group to 4 bits ... and set the USB On The Go HS Global Interrupt priorities to the highest value [1].

   • Go to Project Manager > Advanced Settings and uncheck the Generate Code checkbox for MX_USB_HOST_Init

3. Open a terminal and navigate to the project Middlewares folder [2], once there git clone this repo.

4. Add the include and examples/include folders to the include directories.

5. Open the project with your OS Explorer and go to the Drivers/STM32***_HAL_Driver folder and copy the missing drivers.

   You should add your MCU's drivers, for example: for the STM32F4xx family you can find them here.

6. Edit main.c file and modify it according to this snippet:

//...
/* USER CODE BEGIN Includes */
#include "mdt/examples/all.h"
/* USER CODE END Includes */
//...

void main(void) {

    //...
    /* USER CODE BEGIN 2 */
    MDT_EXAMPLE_term(); //or whatever example you want to run
    /* USER CODE END 2 */
    //...
    
}

Notes

• Enabling any other peripherals could make the system unstable, please do it carefully.

• In Project Properties > C/C++ Build > Settings > MCU GCC Compiler > Preprocessor, the USE_FULL_LL_DRIVER definition should be set.

[1]

In NVIC priority settings, lower value means higher priority.

[2]

Actually you can clone this repo anywhere within the project. Middlewares just seemed the appropiate place, but in case it does not exist you can put it into any folder, just make sure the folder is a Source Folder so its contents get compiled.