对于NUCLEO型开发板不像DISCOVERY型那样配以丰富的外设资源，为此在学习GPIO口使用的基础上，利用开发板所配置的扩展接口来为其添加一个OLED显示屏，这样就可以免去连线的麻烦。开发板的扩展接口的引脚资源配置情况见图1所示，这里所使用的是PA5和PA6。
图1 引脚资源配置
对这2个引脚的配置函数为：
<pre>void OLED_config(void)
{
__HAL_RCC_GPIOA_CLK_ENABLE();
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_PULLUP;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
GPIO_InitStruct.Pin = GPIO_PIN_5|GPIO_PIN_6;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
}</pre>
复制代码为便于引脚输出高低电平的需要，所定义的语句为：
#define OLED_SCLK_Clr() HAL_GPIO_WritePin(GPIOA, GPIO_PIN_5, GPIO_PIN_RESET)
#define OLED_SCLK_Set() HAL_GPIO_WritePin(GPIOA, GPIO_PIN_5, GPIO_PIN_SET)
#define OLED_SDIN_Clr() HAL_GPIO_WritePin(GPIOA, GPIO_PIN_6, GPIO_PIN_RESET)
#define OLED_SDIN_Set() HAL_GPIO_WritePin(GPIOA, GPIO_PIN_6, GPIO_PIN_SET)
以GPIO口模拟I2C发送字节数据的函数为：
<pre>void Write_IIC_Byte(unsigned char IIC_Byte)
{
unsigned char i;
unsigned char m,da;
da=IIC_Byte;
OLED_SCLK_Clr();
for(i=0;i<8;i++)
{
m=da;
m=m&0x80;
if(m==0x80)
{OLED_SDIN_Set();}
else OLED_SDIN_Clr();
da=da<<1;
OLED_SCLK_Set();
OLED_SCLK_Clr();
}
}</pre>
复制代码实现OLED屏初始化的函数为：
<pre>void OLED_Init(void)
{
Write_IIC_Command(0xAE); //display off
Write_IIC_Command(0x20); //Set Memory Addressing Mode
Write_IIC_Command(0x10);
Write_IIC_Command(0xb0);//Set Page Start Address for Page Addressing Mode,0-7
Write_IIC_Command(0xc8);//Set COM Output Scan Direction
Write_IIC_Command(0x00);//---set low column address
Write_IIC_Command(0x10);//---set high column address
Write_IIC_Command(0x40);//--set start line address
Write_IIC_Command(0x81);//--set contrast control register
Write_IIC_Command(0xdf);
Write_IIC_Command(0xa1);//--set segment re-map 0 to 127
Write_IIC_Command(0xa6);//--set normal display
Write_IIC_Command(0xa8);//--set multiplex ratio(1 to 64)
Write_IIC_Command(0x3F);//
Write_IIC_Command(0xa4);//0xa4,Output follows RAM content;0xa5,Output ignores RAM content
Write_IIC_Command(0xd3);//-set display offset
Write_IIC_Command(0x00);//-not offset
Write_IIC_Command(0xd5);//--set display clock divide ratio/oscillator frequency
Write_IIC_Command(0xf0);//--set divide ratio
Write_IIC_Command(0xd9);//--set pre-charge period
Write_IIC_Command(0x22); //
Write_IIC_Command(0xda);//--set com pins hardware configuration
Write_IIC_Command(0x12);
Write_IIC_Command(0xdb);//--set vcomh
Write_IIC_Command(0x20);//0x20,0.77xVcc
Write_IIC_Command(0x8d);//--set DC-DC enable
Write_IIC_Command(0x14);//
Write_IIC_Command(0xaf);//--turn on oled panel
}</pre>
复制代码对显示屏进行清除的函数为：
<pre>void OLED_Clear(void)
{
uint8_t i,n;
for(i=0;i<8;i++)
{
OLED_WR_Byte (0xb0+i,OLED_CMD);
OLED_WR_Byte (0x00,OLED_CMD);
OLED_WR_Byte (0x10,OLED_CMD);
for(n=0;n<128;n++)OLED_WR_Byte(0,OLED_DATA);
}
}</pre>
复制代码实现字符显示输出的函数为：
<pre>void OLED_ShowChar(uint8_t x,uint8_t y,uint8_t chr,uint8_t Char_Size)
{
unsigned char c=0,i=0;
c=chr-' ';
if(x>Max_Column-1){x=0;y=y+2;}
if(Char_Size ==16)
{
OLED_Set_Pos(x,y);
for(i=0;i<8;i++)
OLED_WR_Byte(F8X16[c*16+i],OLED_DATA);
OLED_Set_Pos(x,y+1);
for(i=0;i<8;i++)
OLED_WR_Byte(F8X16[c*16+i+8],OLED_DATA);
}
else
{
OLED_Set_Pos(x,y);
for(i=0;i<6;i++)
OLED_WR_Byte(F6x8[c][i],OLED_DATA);
}
}</pre>
复制代码基于字符显示的字符串显示函数为：
<pre>void OLED_ShowString(uint8_t x,uint8_t y,uint8_t *chr,uint8_t Char_Size)
{
unsigned char j=0;
while (chr[j]!='\0')
{ OLED_ShowChar(x,y,chr[j],Char_Size);
x+=8;
if(x>120){x=0;y+=2;}
j++;
}
}</pre>
复制代码实现OLED屏驱动测试的主程序为：
<pre>int main(void)
{
HAL_Init();
SystemClock_Config();
LED2_GPIO_CLK_ENABLE();
LED1_GPIO_CLK_ENABLE();
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_PULLUP;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
GPIO_InitStruct.Pin = LED2_PIN;
HAL_GPIO_Init(LED2_GPIO_PORT, &GPIO_InitStruct);
GPIO_InitStruct.Pin = LED1_PIN;
HAL_GPIO_Init(LED1_GPIO_PORT, &GPIO_InitStruct);
OLED_config();
OLED_Init();
OLED_Clear();
OLED_ShowString(0,0,"STM32WL55",16);
OLED_ShowString(0,2,"OLED TEST",16);
while (1)
{
HAL_GPIO_TogglePin(LED2_GPIO_PORT, LED2_PIN);
HAL_Delay(100);
HAL_GPIO_TogglePin(LED1_GPIO_PORT, LED1_PIN);
HAL_Delay(100);
}
}</pre>
复制代码经程序的编译和下载，其显示效果如图2所示，说明显示驱动程序正常有效，可以在实际应用中加以使用。
图2 显示效果
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