虽然在PC机中,串口渐行渐远,但是在嵌入式领域,串口仍可以说是如日中天,因为它造价低廉、并且编程也比较方便,在没有显示屏或输入设备的系统上,串口更是不可或缺,和超级终端一道,共同解决了信息显示和输入问题。
经过这几天的努力,在Cortex-M3平台上的.Net Micro Framework的NativeSample移植工作就要一个段落了,目前已实现启动代码、SRAM、时钟(RCC)、中断(NVIC)、SysTick、GPIO、串口、NandFlash(FMSC)等相关功能,这些代码可以说是使TinyClr正常工作的最小集合,有了这些工作做铺垫,下一步就可以移植TinyClr了,如果我们采用的Cortex-M3开发板有2M以上的RAM,那么我们的工作到这一步也许是已经完成90%上了,但是由于资源有限,下一步调试必须为Flash版本,所以未知的工作将很多,并且调试也将变得困难,不管怎么我们的.Net Micro Framework PortingKit之旅还将继续,不过,说心里话,由零开始完成这些工作,虽然艰苦,但是收获颇丰,对ARM开发(尤其是Cortex-M3)的理解更是上了一个层次。
好了,下面我们要说一下串口驱动的开发。
和GPIO开发一样,我们仍需在CortexM3.h中编写串口相关的寄存器代码。
struct CortexM3_Usart
{
static const UINT32 c_MAX_BAUDRATE = 45000000;
static const UINT32 c_MIN_BAUDRATE = 1200;
static const UINT32 c_Base1 = 0x40013800;
static const UINT32 c_Base2 = 0x40004400;
static const UINT32 c_Base3 = 0x40004800;
/****/ volatile UINT16 SR;
static const UINT16 SR_TXE=((UINT16)0x0080);
static const UINT16 SR_TC=((UINT16)0x0040);
static const UINT16 SR_RXNE=((UINT16)0x0020);
UINT16 RESERVED0;
/****/ volatile UINT16 DR;
UINT16 RESERVED1;
/****/ volatile UINT16 BRR;
UINT16 RESERVED2;
/****/ volatile UINT16 CR1;
static const UINT16 CR1_UE_Set = ((UINT16)0x2000); //USART Enable Mask
static const UINT16 CR1_UE_Reset = ((UINT16)0xDFFF); //USART Disable Mask
static const UINT16 CR1_Parity_No = ((UINT16)0x0000);
static const UINT16 CR1_Parity_Even = ((UINT16)0x0400);
static const UINT16 CR1_Parity_Odd = ((UINT16)0x0600);
static const UINT16 CR1_DataBit_8 = ((UINT16)0x0000);
static const UINT16 CR1_DataBit_9 = ((UINT16)0x1000);
static const UINT16 CR1_Mode_Rx = ((UINT16)0x0004);
static const UINT16 CR1_Mode_Tx = ((UINT16)0x0008);
static const UINT16 CR1_CLEAR_Mask = ((UINT16)0xE9F3);
static const UINT16 CR1_PEIE = ((UINT16)0x0100);
static const UINT16 CR1_TXEIE = ((UINT16)0x0080);
static const UINT16 CR1_TCIE = ((UINT16)0x0040);
static const UINT16 CR1_RXNEIE = ((UINT16)0x0020);
UINT16 RESERVED3;
/****/ volatile UINT16 CR2;
static const UINT16 CR2_StopBits_1 = ((UINT16)0x0000);
static const UINT16 CR2_StopBits_0_5 = ((UINT16)0x1000);
static const UINT16 CR2_StopBits_2 = ((UINT16)0x2000);
static const UINT16 CR2_StopBits_1_5 = ((UINT16)0x3000);
static const UINT16 CR2_StopBits_Mask= ((UINT16)0xCFFF); /* USART CR2 STOP Bits Mask */
UINT16 RESERVED4;
/****/ volatile UINT16 CR3;
static const UINT16 CR3_HardwareFlowControl_None = ((UINT16)0x0000);
static const UINT16 CR3_HardwareFlowControl_RTS = ((UINT16)0x0100);
static const UINT16 CR3_HardwareFlowControl_CTS = ((UINT16)0x0200);
static const UINT16 CR3_HardwareFlowControl_RTS_CTS = ((UINT16)0x0300);
static const UINT16 CR3_HardwareFlowControl_Mask = ((UINT16)0xFCFF);
UINT16 RESERVED5;
/****/ volatile UINT16 GTPR;
UINT16 RESERVED6;
};