Some lessons on STM3216 IO port operation

I have taken a lot of detours when using TFT screens recently. Since TFT screens are all 16-bit, most of them use a set of IO ports corresponding to 16 data bits to transmit data through parallel ports. Recently, due to the shortage of IO ports, I wanted to change to a serial port, but found that the serial port refreshes the screen too slowly, so I finally changed to an 8-bit parallel port. However, the registers for operating the IO port of STM32 are 16 bits. That is to say, if you use a parallel port, although only 8 bits are used to transmit data together, the operation is still 16 bits together. Although there are 8 bits that are not used, they are still operated together when transmitting data, and the values ​​of the unused 8 bits will be overwritten together.

 #define DATAOUT(x) GPIOB->ODR=x; //Data output

As above, when the macro is called, the entire B port is operated together.

Method 1: ODR configuration method, you can directly use GPIO->ODR = value << N; to perform output operations on the corresponding IO port.
However, the hardware must ensure that:
1. The remaining IO ports on this function port (such as GPIOA) are not used as ordinary IO output ports
2. GPIO ports outside the rows and columns are either common IO input ports or function ports. Function ports are UART, USB, PWM, ADC, etc. When operating the ODR of GPIO, it will not affect the function port.
That is to say, for example, if the high 8 bits of port B are selected, then IO ports 8--15 are selected to drive TFT, but IO ports 0-7 cannot be used as ordinary output IO ports, but can be set as input, or UART, USB, PWM, ADC and other functions.

Method 2

The IO port can be operated individually by bit operation, but the data refresh speed is very slow.

void WriteData(u8 data)
{
   // Operate the IO ports connected to the LCD separately, the order is from high to low
    GPIO_WriteBit(GPIO number, Pin number, (data & 0x80) >> 7 ); 
    GPIO_WriteBit(GPIO number, Pin number, (data & 0x40) >> 6 ); 
    GPIO_WriteBit(GPIO number, Pin number, (data & 0x20) >> 5 ); 
    GPIO_WriteBit(GPIO number, Pin number, (data & 0x10) >> 4 ); 
    GPIO_WriteBit(GPIO number, Pin number, (data & 0x08) >> 3 ); 
    GPIO_WriteBit(GPIO number, Pin number, (data & 0x04) >> 2 ); 
    GPIO_WriteBit(GPIO number, Pin number, (data & 0x02) >> 1 ); 
    GPIO_WriteBit(GPIO number, Pin number, data & 0x01);
 }

Using this method will not affect the bottom 8 bits, but the refresh speed will be very slow.