4X4矩陣鍵盤掃描：

1. 4根行線的GIO均設為Output，根列線的GIO均設為Input；

2. 4根行線的GIO分別置為0111、1011、1101、1110，讀逐一讀取列線GIO的值，可確定是哪一個按鍵；

電路圖如下：

注意：

1. 圖中用作輸入的GIO，一定要有一個上拉電阻。

2. 晶片中的每一個引腳是否用作了GPIO口來用，需配置晶片的暫存器，使引腳當作GPIO口來使用，才會有效。

測試程式碼如下：

#define KEY_GIO_ROW_1	37
#define KEY_GIO_ROW_2	33
#define KEY_GIO_ROW_3	32
#define KEY_GIO_ROW_4	35
#define KEY_GIO_COL_1	22
#define KEY_GIO_COL_2	23
#define KEY_GIO_COL_3	24
#define KEY_GIO_COL_4	36
int scanKey()
{
	int keyValue = 0;
	int col1Value=0,col2Value=0,col3Value=0,col4Value=0,row1Value=0,row2Value=0,row3Value=0,row4Value=0;
	static int press1=0,press2=0,press3=0,press4=0;
	static int press5=0,press6=0,press7=0,press8=0;
	static int press9=0,press10=0,press11=0,press12=0;
	static int press13=0,press14=0,press15=0,press16=0;

	dm365SetGPIO(KEY_GIO_ROW_1, 0);
	dm365SetGPIO(KEY_GIO_ROW_2, 1);
	dm365SetGPIO(KEY_GIO_ROW_3, 1);
	dm365SetGPIO(KEY_GIO_ROW_4, 1);
	col1Value = dm365GetGPIO(KEY_GIO_COL_1);
	col2Value = dm365GetGPIO(KEY_GIO_COL_2);
	col3Value = dm365GetGPIO(KEY_GIO_COL_3);
	col4Value = dm365GetGPIO(KEY_GIO_COL_4);
	keyValue = col1Value | (col2Value << 1) | (col3Value << 2) | (col4Value << 3);
//	printf("=1==keyValue = %x\n",keyValue);
	switch(keyValue)
	{
		case 0x0E:
			{
				if(!press1)
				{
					press1 = 1;
					printf("KEY 1\n");
				}
			}
			break;
		case 0x0D:
			{
				if(!press2)
				{
					press2 = 1;
					printf("KEY 2\n");
				}
			}
			break;
		case 0x0B:
			{
				if(!press3)
				{
					press3 = 1;
					printf("KEY 3\n");
				}
			}
			break;
		case 0x07:
			{
				if(!press4)
				{
					press4 = 1;
					printf("KEY 4\n");
				}
			}
			break;
		default:
			{
				press1 = 0;
				press2 = 0;
				press3 = 0;
				press4 = 0;
			}
			break;
	}

	dm365SetGPIO(KEY_GIO_ROW_1, 1);
	dm365SetGPIO(KEY_GIO_ROW_2, 0);
	dm365SetGPIO(KEY_GIO_ROW_3, 1);
	dm365SetGPIO(KEY_GIO_ROW_4, 1);
	col1Value = dm365GetGPIO(KEY_GIO_COL_1);
	col2Value = dm365GetGPIO(KEY_GIO_COL_2);
	col3Value = dm365GetGPIO(KEY_GIO_COL_3);
	col4Value = dm365GetGPIO(KEY_GIO_COL_4);
	keyValue = col1Value | (col2Value << 1) | (col3Value << 2) | (col4Value << 3);
//	printf("=2==keyValue = %x\n",keyValue);
	switch(keyValue)
	{
		case 0x0E:
			{
				if(!press5)
				{
					press5 = 1;
					printf("KEY 5\n");
				}
			}
			break;
		case 0x0D:
			{
				if(!press6)
				{
					press6 = 1;
					printf("KEY 6\n");
				}
			}
			break;
		case 0x0B:
			{
				if(!press7)
				{
					press7 = 1;
					printf("KEY 7\n");
				}
			}
			break;
		case 0x07:
			{
				if(!press8)
				{
					press8 = 1;
					printf("KEY 8\n");
				}
			}
			break;
		default:
			{
				press5 = 0;
				press6 = 0;
				press7 = 0;
				press8 = 0;
			}
			break;
	}

	dm365SetGPIO(KEY_GIO_ROW_1, 1);
	dm365SetGPIO(KEY_GIO_ROW_2, 1);
	dm365SetGPIO(KEY_GIO_ROW_3, 0);
	dm365SetGPIO(KEY_GIO_ROW_4, 1);
	col1Value = dm365GetGPIO(KEY_GIO_COL_1);
	col2Value = dm365GetGPIO(KEY_GIO_COL_2);
	col3Value = dm365GetGPIO(KEY_GIO_COL_3);
	col4Value = dm365GetGPIO(KEY_GIO_COL_4);
	keyValue = col1Value | (col2Value << 1) | (col3Value << 2) | (col4Value << 3);
//	printf("=3==keyValue = %x\n",keyValue);
	switch(keyValue)
	{
		case 0x0E:
			{
				if(!press9)
				{
					press9 = 1;
					printf("KEY 9\n");
				}
			}
			break;
		case 0x0D:
			{
				if(!press10)
				{
					press10 = 1;
					printf("KEY 10\n");
				}
			}
			break;
		case 0x0B:
			{
				if(!press11)
				{
					press11 = 1;
					printf("KEY 11\n");
				}
			}
			break;
		case 0x07:
			{
				if(!press12)
				{
					press12 = 1;
					printf("KEY 12\n");
				}
			}
			break;
		default:
			{
				press9 = 0;
				press10 = 0;
				press11 = 0;
				press12 = 0;
			}
			break;
	}

	dm365SetGPIO(KEY_GIO_ROW_1, 1);
	dm365SetGPIO(KEY_GIO_ROW_2, 1);
	dm365SetGPIO(KEY_GIO_ROW_3, 1);
	dm365SetGPIO(KEY_GIO_ROW_4, 0);
	col1Value = dm365GetGPIO(KEY_GIO_COL_1);
	col2Value = dm365GetGPIO(KEY_GIO_COL_2);
	col3Value = dm365GetGPIO(KEY_GIO_COL_3);
	col4Value = dm365GetGPIO(KEY_GIO_COL_4);
	keyValue = col1Value | (col2Value << 1) | (col3Value << 2) | (col4Value << 3);
//	printf("=4==keyValue = %x\n",keyValue);
	switch(keyValue)
	{
		case 0x0E:
			{
				if(!press13)
				{
					press13 = 1;
					printf("KEY 13\n");
				}
			}
			break;
		case 0x0D:
			{
				if(!press14)
				{
					press14 = 1;
					printf("KEY 14\n");
				}
			}
			break;
		case 0x0B:
			{
				if(!press15)
				{
					press15 = 1;
					printf("KEY 15\n");
				}
			}
			break;
		case 0x07:
			{
				if(!press16)
				{
					press16 = 1;
					printf("KEY 16\n");
				}
			}
			break;
		default:
			{
				press13 = 0;
				press14 = 0;
				press15 = 0;
				press16 = 0;
			}
			break;
	}


	return keyValue;
}
void *KeyMngThread()
{
	int resetValue = 1;
	int resetCout = 0;
	int alarmInValue = 1;
	int alarmInCout = 0;
	while(1)
	{
		resetValue = dm365GetGPIO(GIO_RESET);
		if(0 == resetValue)
		{
			resetCout++;
		}
		else if(1 == resetValue)
		{
			resetCout = 0;
		}
		if(resetCout == 30)
		{
			resetCout = 0;
			system("rm -f /mnt/nand/sysenv.cfg");
			system("/bin/sync");
//			System("reboot");
			system("/tmp/shutdown -r now \n");
		}
		alarmInValue = dm365GetGPIO(GIO_ALARM_IN);
		if(0 == alarmInValue)
		{
			dm365SetGPIO(GIO_LED,0);	//control led off .
		}
		else if(1 == alarmInValue)
		{
			dm365SetGPIO(GIO_LED,1);	//control led on .
		}

		scanKey();

		usleep(100000);
	}

}
 

dm365GetGPIO( )中將GPIO預設設定為Input,

通過字元裝置驅動實現應用層操作底層GPIO。