IO6		=	BAT_VOLTAGE		读取电池电压，作为电量的粗略判断
IO7		=	ADC_CTL			开关读取电压的MOS管，防止电池电量跑光
IO15	=	POW_CTL			开关各种外围芯片的电源
IO8		= 	I2C_SDA			
IO19 	= 	Button0			按钮信号0
IO20	=	Button1			按钮信号1，两个按钮的状态：00无按键；10左键；01右键；11中键
~~IO41	=	LED_CTL			控制状态LED灯
~~IO46	=	SD_CS			sd卡片选
IO9	=		I2C_SCL			
IO10	=	TFT_PWM			TFT显示屏背光亮度控制
IO11	=	SPI_SDO(MISO)
IO12	=	SPI_SDI(MOSI)
IO13	=	SPI_CS
IO14	= 	SPI_DC
IO21	= 	SPI_SCL
IO47	= 	TFE_RST			TFT显示屏复位引脚
~~IO45	= 	USB_PLUGIN_DETECT	检测USB是否插入，高电平有usb

新增或修改的IO口
IO4		=	SD_CMD
IO5		=	SD_CLK
IO16	=	ESP_TX
IO17	= 	ESP_RX
IO18	=	USB_PLUGIN_DETECT
IO42	=	LED_CTL
IO41	=	SD_DATA0
IO40	=	SD_DATA1
IO39	=	SD_DATA2
IO38	=	SD_DATA3
IO48	=	SD_CON