Preface

Previously, I found a piece of Wildfire’s STM32F429-V1 core board on Xianyu, and it was this:

However, I feel very uncomfortable after using it, and basically cannot use it independently. The main reasons are as follows:

• There is no SD card slot, which is the most unacceptable.
• The performance of SDRAM is very poor, and Brust access is basically unusable. I don’t know why, because theoretically, the performance of ISSI SDRAM is still good, and it also supports 8-length burst access.
• There are no fuses or other current limiting measures on the power supply. Once connected incorrectly or short-circuited, GG.
• There is no dedicated power supply pin header, and there is nowhere to get power when using DuPont cable to connect the module.
• There is no 5V power pin on the SWD debug interface, which means that if you use an RGB display, you cannot rely solely on the debugger for power, and you must also connect it to USB. . .
• There are no FMC-related pins, which means that the display screen of the MCU interface cannot be connected, and then all the LTDC pins are printed out. . . . What's the picture? Doesn't the core board have an FPC interface?

There are many other issues, but I won’t go into them here because this is not a complaint post.

In short, in order not to let my money go to waste, I drew this simple base board to make it less uncomfortable to use. . .

This project is drawn more casually. There is actually a lot of space on the board. If you are interested, you can fork it and add other things.

characteristic

• Onboard ST-Link V2.1, and leads to SWD interface
• TYPE-C power supply/communication interface with self-restoring fuse
• Export all available IO of the core board
• A USB-Host interface
• A serial LCD interface compatible with most of Taobao's small display modules.
• A universal camera interface, suitable for the cheap OV7670/7725 camera on Taobao (yes, the one that costs 9 yuan on Uxin)
• an RGB light
• Three user buttons and one BOOT button
• Dedicated module power supply pin header
• A 24C02 EEPROM can conveniently store data such as touch screen calibration
• RTC backup battery
• a passive buzzer
• Finally, the most important thing is the MicroSD card slot! ! !

Precautions

The built-in ST-Link and the SWD interface of the core board are led out through the same double row of pins. They are not connected by default and need to be connected together through a short-circuit cap. The advantage of this is that you can use an external debugger even if you don't solder ST-Link (after all, STM32F103CB is very expensive now). Or directly use the ST-LINK on the board to debug other development boards.

Serial LCD interface

I would like to say a few more words about the LCD interface on the board.

Most of the small LCD display modules on Taobao now, such as the 0.96-inch/1.13-inch/1.3-inch/1.54-inch ST7789IPS, and the 1.44-inch/1.8-inch ST7735, all use the SPI protocol. In the interface line sequence, the first four are as follows:

> GND VCC SCK MOSI

Then there are the remaining 4 auxiliary signals for CS, RST, DC, BLK and the like.

Most OLED modules also have this line sequence, but the communication protocol has changed to IIC.

So I designed an LCD interface like this:

It can be seen that the first column leads to the hardware SPI interface according to this line sequence, and the second column leads to the I2C interface. In this case, these common display modules, whether they are TFT modules or OLED modules, can be directly plugged into this interface for use. , no need to use Dupont wire to connect.

If you want to design your own LCD module, you can also design it according to this interface. Because this interface has both hardware I2C and full-duplex SPI interfaces, as well as 7 redundant IOs, it can basically meet all serial screen design needs.

picture

Finished product

Fit photos

Camera application

Finally, there is no need to connect a special wire to power the screen.

Of course you can also play like me