STM32F103 & ILI9341 with SPI/DMA & overclocking

This project has blog post here: http://www.stupid-projects.com/driving-an-ili9341-lcd-with-an-overclocked-stm32f103/

This project is about an stm32f103 (blue-pill) driving an ILI9341 LCD with SPI and DMA. On top of that the stm32 is also overclocked from 72 to 128MHz. The lcd driver is in source/libs/ILI9341, but it's using another SPI drivers I've implemented which is located in source/dev_spi.c.

The LCD module used is: TJCTM24028-SPI

The SPI driver is using DMA for both TX/RX and you can use it for all available SPI options:

• SPI1: on GPIOA (see en_spi_mode::DEV_SPI1_GPIOA)
• SPI1: on GPIOB (see en_spi_mode::DEV_SPI1_GPIOB)
• SPI2: on GPIOB (see en_spi_mode::DEV_SPI2)

The pinout is used for the STM32 is:

• common for all modes:

  • PA0: LED
  • PA2: RESET
  • PA3: D/C

• en_spi_mode::DEV_SPI1_GPIOA (default):

  • PA4: CS
  • PA5: SCK
  • PA6: SDO(MISO)
  • PA7: SDI(MOSI)

• en_spi_mode::DEV_SPI1_GPIOB:

  • PB2: CS
  • PB3: SCK
  • PB4: SDO(MISO)
  • PB5: SDI(MOSI)

• en_spi_mode::DEV_SPI2:

  • PB12: CS
  • PB13: SCK
  • PB14: SDO(MISO)
  • PB15: SDI(MOSI)

• serial port (115200-8-N-1):

  • PA9: Tx
  • PA10: Rx

Note: The ILI9341 is both 3V3 and 5V. On the back of the module there are two SMD pads (J1). This supposed to be soldered when you power the module, but I haven't shorted those.

You can either connect the VCC on an external 3V3 PSU, but in my case I've just connected the LCD's VCC to the 3.3 pin of the stm32f013 and it worked fine.

What the code does

The code in main is very simple and you won't see any graphics. If it works, you'll only see a yellow screen. This is because I wanted to benchmark the framerate of filling the screen without any additional calculations that spend cpu cycles. The code that does the drawing is inside main():

LCD_setCursor(0, 0);
LCD_fillScreen(YELLOW);

The above code runs on every main loop and there's also a counter glb.fps that increments on every screen draw. Finally, in the SysTick_Handler() interrupt in stm3210x_it.c every second the glb.fps is stored and reset and then the code prints the fps value.

Therefore, if you need more advanced graphics, the library is there and you can add any code you like.

Also, there's a dbg_uart_parser() function in main.c that is ready to be used to parse and execute commands from the uart.

Overclocking

I've done two benchmarks. The one with the default maximum frequency (72MHz) and the other with the stm32f103 overclocked to 128MHz. These are the FPS I got for each frequency (using -O3 for GCC optimization):

• 72MHz: 29-30 fps
• 128MHz: 52-53 fps

I haven't seen any difference in the fps when using other optimization flags.

Note: When stm32f103 is overclocked then the USB is not working as the available divider options don't achieve the 48MHz it needs.

How to compile and flash

You need cmake to build this project either on Windows or Linux. To setup the cmake properly follow the instructions from here. Then edit the cmake/TOOLCHAIN_arm_none_eabi_cortex_m3.cmake file and point TOOLCHAIN_DIR to the correct GCC path.

e.g. on Windows

set(TOOLCHAIN_DIR C:/opt/gcc-arm-none-eabi-4_9-2015q3-20150921-win32)

or on Linux

set(TOOLCHAIN_DIR /opt/gcc-arm-none-eabi-4_9-2015q3)

Then on Windows run build.cmd or on Linux run ./build.bash and the .bin and .hex files should be created in the build-stm32/src folder. Also, a .cproject and .project files are created if you want to edit the source code.

To flash the HEX file in windows use st-link utility like this: "C:\Program Files (x86)\STMicroelectronics\STM32 ST-LINK Utility\ST-LINK Utility\ST-LINK_CLI.exe" -c SWD -p build-stm32\src\stm32f103_wifi_usb_psu.hex -Rst

To flash the bin in Linux: st-flash --reset write build-stm32/src/stm32f103_wifi_usb_psu.bin 0x8000000

FW details

• CMSIS version: 5.3.0
• StdPeriph Library version: 3.6.1