DSP28335 I2C接口应用(11页).doc

-DSP28335 I2C接口应用-第 11 页DSP I2C 应用说明1.示例程序中几种状态第一次看i2c_eeprom示例程序，对程序中的MsgStatus信息状态切换非常懵懂，为什么要有这几个状态？状态切换顺序如何安排？一大堆的状态，让人有些摸不着头脑。先把程序中的头文件涉及的7种状态分析一下。/ I2C Message Commands for I2CMSG struct#define I2C_MSGSTAT_INACTIVE 0x0000 /未激活状态：一般成功发送数据或者/接受数据后可以设置信息状态为此状态，告诉用户可进行下一次的写数据或读数据。#define I2C_MSGSTAT_SEND_WITHSTOP 0x0010 /发送带停止位数据：这是为写数据而设/的状态，写入地址和数据之后发个停止位告诉存储器数据写入完毕。#define I2C_MSGSTAT_WRITE_BUSY 0x0011 /写数据忙状态：在将待写的数据放入/缓存后，就可以使能IIC传输数据了，然后把信息状态设为该状态，意在告诉用户：数据/已经在传送过程中。当然是否传送完毕，还需要通过查询SCD位来判断。#define I2C_MSGSTAT_SEND_NOSTOP 0x0020/发送无停止位数据：这个状态是为了读/取数据而设的，有查阅过AT24C1024EEPROM存储器使用手册的读者知道，在读数据之前/要发送数据的地址，发完地址不能产生停止位，这是存储器硬件设计决定的。设为这个状/态意在告诉读者，可以发送要读取的数据的地址了。#define I2C_MSGSTAT_SEND_NOSTOP_BUSY 0x0021/发送无停止位数据忙状态：这个状态是/为了读取数据而设的,似于I2C_MSGSTAT_WRITE_BUSY，说明地址数据已经在传送过程中。/传送是否成功，还要看ARDY的状态。#define I2C_MSGSTAT_RESTART 0x0022/重发开始位状态：这个状态也是为读取/数据而设。我们知道，读取存储器数据主要分两个步骤：第一，发送START位+设备地址/+数据地址+无停止位。第二，再发START位+设备地址，紧接着存储器发送数据到IIC接收/缓存器(I2CDRR)，接收到设定好的数据数量（I2CCNT值）时输出停止位STOP./值得注意的是：理论上写完数据就能马上读取 数据 ，但事实上EEPROM存储器仍需要一/定延时来存储数据，约有2ms左右。通过示波器可以观察到，写完数据后，并不能马上/成功读取数据，也就是说读数据的第一步骤要重复好几次（总线为50K时，大约要重复/8次）才能成功。#define I2C_MSGSTAT_READ_BUSY 0x0023/读取数据忙状态：这个状态是为读取数/据而设。在读数据的第二步骤中，发完START位+设备地址后，就设为这一状态。意在说/明IIC开始等待接收固定数量（I2CCNT值）的数据。可以通过查询ARDY位判断。/头文件中的其他定义应该没什么大问题了！2.AT24C1024 EEPROM读写数据格式（1）AT24C1024设备地址：10100A1P0R/W（2）单字节写入：START -> 发送从设备地址(写控制码R/W=0) -> 处理Ack -> 发送字节地址 -> 处理Ack -> 发送1字节数据 -> 处理Ack -> STOP。如下图：（3）按页写入：START -> 发送从设备地址(写控制码R/W=0) -> 处理Ack -> 发送字节地址 -> 处理Ack -> 发送1字节数据 -> 处理Ack-> 发送第2字节数据 -> 处理Ack-> 发送第3字节数据 -> 处理Ack直到发完X字节 -> STOP。如下图。注意，连续写入的数据字节数不能超过每页所能容下的总量。如果写入的数据超过一页的长度，将发生回卷，即从EEPROM的0地址处进行数据覆盖。比如，AT24C1024有512页，每页最大容纳256字节。超过这个长度，地址指针将从每页首地址重新开始。（4）随机单字节读取：第一步：发START -> 发送从设备地址(写控制码R/W=0) -> 处理Ack -> 发送字节地址高位 -> 处理Ack -> 发送字节地址低位 -> 处理Ack ->第二步：发START -> 发送器件地址(读控制码R/W=1) -> 处理Ack -> 接收1字节数据 -> STOP。（5）随机连续读取：在随机单字节读取操作的STOP信号发送之前，加入若干个 -> 发送Ack -> 接收1字节数据 即可实现。（6）当前位置单字节读取：START -> 发送从设备地址(读控制码) -> 处理Ack -> 发送字节地址 -> 处理Ack -> 接收1字节数据 -> STOP。当前指的是之前进行过读取操作但是没有发送STOP信号，EEPROM芯片内部指针所在的位置即为当前位置。（7）当前位置连续读取：在当前位置单节读取操作的STOP信号发送之前，加入若干个 -> 发送Ack -> 接收1字节数据 即可实现。备注：部分内容引用百度文库中的I2C读写流程文档3.主程序说明及流程图详细的注释可以参见程序附录，这里主要解释一下设备地址取0x50的缘由。从AT24C1024的数据手册可知，设备地址为。而在程序中设置的地址是0x50，即0B0101 0000。看似不妥，其实，这个例子中设备地址采用7位地址模式，这样只取0x50的低7位作为设备地址的高七位，设备地址的最低位R/W则由寄存器I2CMDR中的TRX位决定。这样读数据时设备地址为0B1010 0001，写数据时设备地址改为0B1010 0000。通过示波器可以验证这些数据。问题1：每次检测到SCD中断时，也就是顺利发完指定数量的数据或者接收指定数量的数据了，理论上I2caRegs.I2CCNT=0，但是本人设了几个中断点去观察该寄存器的值，发现总是不为零。通过观察I2caRegs.I2CFFTX.bit.TXFFST和I2caRegs.I2CFFRX.bit.RXFFST，可以发现这两个寄存器为零时，I2caRegs.I2CCNT也不为零。由此可知，I2CCNT不能实时反映发送/接收存储器中数据的数量，不过可以用TXFFST/RXFFST来代替。图1 主程序流程图,图2为写数据程序流程图，图3为读数据程序流程图，图4为中断函数流程图。图1 主程序流程图图2写数据程序流程图 图3读数据程序流程图图4中断函数流程图4.程序附录/可以用以下代码替换示例程序Example_280xI2c_eeprom.c中的代码，再进行调试。/该程序跟原始程序没多大区别，主要改变为：引入几个统计变量，改变发送数据长度为2字节/ TI File $Revision: /main/5 $/ Checkin $Date: April 4, 2007 17:18:36 $/ FILE: Example_280xI2c_eeprom.c/ TITLE: DSP280x I2C EEPROM Example/ ASSUMPTIONS:/ This program requires the DSP280x header files./ This program requires an external I2C EEPROM connected to/ the I2C bus at address 0x50./ As supplied, this project is configured for "boot to SARAM"/ operation. The 280x Boot Mode table is shown below./ For information on configuring the boot mode of an eZdsp,/ please refer to the documentation included with the eZdsp,/ Boot GPIO18 GPIO29 GPIO34/ Mode SPICLKA SCITXDA/ SCITXB/ Flash 1 1 1/ SCI-A 1 1 0/ SPI-A 1 0 1/ I2C-A 1 0 0/ ECAN-A 0 1 1/ SARAM 0 1 0 <- "boot to SARAM"/ OTP 0 0 1/ I/0 0 0 0/ DESCRIPTION:/ This program will write 1-14 words to EEPROM and read them back./ The data written and the EEPROM address written to are contained/ in the message structure, I2cMsgOut1. The data read back will be/ contained in the message structure I2cMsgIn1./ CODE MODIFICATIONS ARE REQUIRED FOR 60 MHZ DEVICES (In/ DSP280x_Examples.h in the common/include/ directory, set/ #define CPU_FRQ_60MHZ to 1, and #define CPU_FRQ_100MHZ to 0)./ This program will work with the on-board I2C EEPROM supplied on/ the F280x eZdsp./ Original Author: D.F./ $TI Release: DSP280x Header Files V1.60 $/ $Release Date: December 3, 2007 $#include "DSP280x_Device.h" / DSP280x Headerfile Include File#include "DSP280x_Examples.h" / DSP280x Examples Include File/ Note: I2C Macros used in this example can be found in the/ DSP280x_I2C_defines.h file/ Prototype statements for functions found within this file.void I2CA_Init(void);Uint16 I2CA_WriteData(struct I2CMSG *msg);Uint16 I2CA_ReadData(struct I2CMSG *msg);interrupt void i2c_int1a_isr(void);void pass(void);void fail(void);#define I2C_SLAVE_ADDR 0x50 /EEPROM地址#define I2C_NUMBYTES 2 /为方便示波器观察，设置发送2字节的数据#define I2C_EEPROM_HIGH_ADDR 0x11 /数据的写入地址高位#define I2C_EEPROM_LOW_ADDR 0x0F /数据的写入地址低位/ Global variables/全局变量/ Two bytes will be used for the outgoing address,/有2个字节是地址/ thus only setup 14 bytes maximum/最多只能设置14字节数据struct I2CMSG I2cMsgOut1=I2C_MSGSTAT_SEND_WITHSTOP,/初始状态为：发送带停止位数据 I2C_SLAVE_ADDR, I2C_NUMBYTES, I2C_EEPROM_HIGH_ADDR, I2C_EEPROM_LOW_ADDR, 0xff, / Msg Byte 01 0x3F, / Msg Byte 02 0x56, / Msg Byte 03 0x78, / Msg Byte 04 0x9A, / Msg Byte 05 0xBC, / Msg Byte 06 0xDE, / Msg Byte 07 0xF0, / Msg Byte 08 0x11, / Msg Byte 09 0x10, / Msg Byte 10 0x11, / Msg Byte 11 0x12, / Msg Byte 12 0x13, / Msg Byte 13 0x12, / Msg Byte 14struct I2CMSG I2cMsgIn1= I2C_MSGSTAT_SEND_NOSTOP, I2C_SLAVE_ADDR, I2C_NUMBYTES, I2C_EEPROM_HIGH_ADDR, I2C_EEPROM_LOW_ADDR;struct I2CMSG *CurrentMsgPtr;/ Used in interruptsUint16 PassCount;Uint16 FailCount;Uint16 ARDY_ISRC_NACK_number=0; /统计ARDY中断源引起的中断中NACK次数Uint16 SCD_ISRC_number=0; /统计SCD中断源引起的中断次数Uint16 ARDY_ISRC_number=0; /统计ARDY中断源引起的中断次数Uint16 all_ISRC_number=0; /统计所有中断源引起的中断次数Uint16 Write_load_num=0; /统计写数据函数调用次数Uint16 Read_load_num1=0; /统计读数据函数调用次数1第一步骤 Uint16 Read_load_num2=0; /统计读数据函数调用次数2第二步骤void main(void) Uint16 Error; Uint16 i; CurrentMsgPtr = &I2cMsgOut1;/ Step 1. Initialize System Control:/ PLL, WatchDog, enable Peripheral Clocks/ This example function is found in the DSP280x_SysCtrl.c file. InitSysCtrl();/ Step 2. Initalize GPIO:/ This example function is found in the DSP280x_Gpio.c file and/ illustrates how to set the GPIO to it's default state./ InitGpio();/ Setup only the GP I/O only for I2C functionality InitI2CGpio();/ Step 3. Clear all interrupts and initialize PIE vector table:/ Disable CPU interrupts DINT;/ Initialize PIE control registers to their default state./ The default state is all PIE interrupts disabled and flags/ are cleared./ This function is found in the DSP280x_PieCtrl.c file. InitPieCtrl();/ Disable CPU interrupts and clear all CPU interrupt flags: IER = 0x0000; IFR = 0x0000;/ Initialize the PIE vector table with pointers to the shell Interrupt/ Service Routines (ISR)./ This will populate the entire table, even if the interrupt/ is not used in this example. This is useful for debug purposes./ The shell ISR routines are found in DSP280x_DefaultIsr.c./ This function is found in DSP280x_PieVect.c. InitPieVectTable();/ Interrupts that are used in this example are re-mapped to/ ISR functions found within this file. EALLOW;/ This is needed to write to EALLOW protected registers PieVectTable.I2CINT1A = &i2c_int1a_isr; EDIS; / This is needed to disable write to EALLOW protected registers/ Step 4. Initialize all the Device Peripherals:/ This function is found in DSP280x_InitPeripherals.c/ InitPeripherals(); / Not required for this example I2CA_Init();/ Step 5. User specific code / Clear Counters PassCount = 0; FailCount = 0; / Clear incoming message buffer for (i = 0; i < I2C_MAX_BUFFER_SIZE; i+) I2cMsgIn1.MsgBufferi = 0x0000;/ Enable interrupts required for this example/ Enable I2C interrupt 1 in the PIE: Group 8 interrupt 1 PieCtrlRegs.PIEIER8.bit.INTx1 = 1;/ Enable CPU INT8 which is connected to PIE group 8 IER |= M_INT8; EINT; / Application loop for(;) / Write data to EEPROM section / / Check the outgoing message to see if it should be sent. / In this example it is initialized to send with a stop bit. if(I2cMsgOut1.MsgStatus = I2C_MSGSTAT_SEND_WITHSTOP) Write_load_num+; Error = I2CA_WriteData(&I2cMsgOut1); / If communication is correctly initiated, set msg status to busy/如果通信已经正确初始化，设置msg状态为忙，并 / and update CurrentMsgPtr for the interrupt service routine. /更新作为中断服务路径的指针CurrentMsgPtr。 / Otherwise, do nothing and try again next loop. Once message is /否则，不做任何操作，等待下一次重新写数据。一旦信息正确 / initiated, the I2C interrupts will handle the rest. Search for /初始化，I2C中断将处理接下来的事情。可以在 / ICINTR1A_ISR in the i2c_eeprom_isr.c file. /i2c_eeprom_isr.c文件中找到ICINTR1A_ISR。 if (Error = I2C_SUCCESS) /数据已成功放入缓存寄存器 CurrentMsgPtr = &I2cMsgOut1; /改变指针路径 I2cMsgOut1.MsgStatus = I2C_MSGSTAT_WRITE_BUSY; /设为发送数据忙状态 / end of write section / Read data from EEPROM section /该过程包括两次发送START位，第一次发送地址 / Check outgoing message status. Bypass read section if status is / not inactive. if (I2cMsgOut1.MsgStatus = I2C_MSGSTAT_INACTIVE) / Check incoming message status. if(I2cMsgIn1.MsgStatus = I2C_MSGSTAT_SEND_NOSTOP) Read_load_num1+; / EEPROM address setup portion while(I2CA_ReadData(&I2cMsgIn1) != I2C_SUCCESS) / Maybe setup an attempt counter to break an infinite while /这里可以设置一个计数器用于终止可能存在的无限循环。 / loop. The EEPROM will send back a NACK while it is performing/当EEPROM忙于处理写数据操作时，将返回一个NACK。 / a write operation. Even though the write communique is /对DSP来说，此刻写操作已经完成。但是，EEPROM仍需要 / complete at this point, the EEPROM could still be busy /一定时间完成数据的烧写1.8ms左右。在EEPROM完成烧写之前，都会 / programming the data. Therefore, multiple attempts are /返回NACK，告诉DSP它还在忙。因此，DSP需要多次尝试，直到 / necessary. /EEPROM空闲了，并返回ACK确认为止。 / Update current message pointer and message status CurrentMsgPtr = &I2cMsgIn1; I2cMsgIn1.MsgStatus = I2C_MSGSTAT_SEND_NOSTOP_BUSY;/第一次发送START成功，即地址数据已发送成功，给发无停止位数据忙状态，作为第二次发送START位标志 / Once message has progressed past setting up the internal address/一旦成功写入EEPROM地址，便可以再次发送START起始位 / of the EEPROM, send a restart to read the data bytes from the /然后从EEPROM存储器中读取数据。 / EEPROM. Complete the communique with a stop bit. MsgStatus is /DSP采可用一个停止位来结束数据接收。 / updated in the interrupt service routine. /msg状态在中断程序中被更新了。 else if(I2cMsgIn1.MsgStatus = I2C_MSGSTAT_RESTART) /该状态是在中断服务程序中态被赋予 Read_load_num2+; / Read data portion while(I2CA_ReadData(&I2cMsgIn1) != I2C_SUCCESS) / Maybe setup an attempt counter to break an infinite while / loop. / Update current message pointer and message status CurrentMsgPtr = &I2cMsgIn1; I2cMsgIn1.MsgStatus = I2C_MSGSTAT_READ_BUSY;/第二次发送START，且数据接收成功，给下一个状态-读忙，作为中断中读取接收缓存中数据的标志 / end of read section / end of for(;) / end of mainvoid I2CA_Init(void) / Initialize I2C I2caRegs.I2CSAR = 0x0050;/ Slave address - EEPROM control code #if (CPU_FRQ_100MHZ) I2caRegs.I2CPSC.all = 9;/ Prescaler - need 7-12 Mhz on module clk #endif #if (CPU_FRQ_60MHZ) I2caRegs.I2CPSC.all = 6;/ Prescaler - need 7-12 Mhz on module clk #endif I2caRegs.I2CCLKL = 95;/ NOTE: must be non zero I2caRegs.I2CCLKH = 95;/ NOTE: must be non zero I2caRegs.I2CIER.all = 0x24;/ Enable SCD & ARDY interrupts I2caRegs.I2CMDR.all = 0x0020;/ Take I2C out of reset/ Stop I2C when suspended /0b0000 0000 0010 0000，NACKMOD=0，FREE=0中断产生时IIC停止运行，STT=0不产生开始位， /STP=0不产生停止位,MST=0从模式,TRX=0接收模式，XA=0 七位地址模式，RM=0不重复,DLB=0无回来 /IRS=1使能I2C模块，STB=0模块未处在开始字节模式,FDF=0自由数据格式被禁止 /注意：TRX决定AT24C1024设备地址中的R/W，这里R/W=1读数据 I2caRegs.I2CFFTX.all = 0x6000;/ Enable FIFO mode and TXFIFO I2caRegs.I2CFFRX.all = 0x2040;/ Enable RXFIFO, clear RXFFINT, return;Uint16 I2CA_WriteData(struct I2CMSG *msg) Uint16 i; / Wait until the STP bit is cleared from any previous master communication. / Clearing of this bit by the module is delayed until after the SCD bit is / set. If this bit is not checked prior to initiating a new message, the / I2C could get confused. if (I2caRegs.I2CMDR.bit.STP = 1) return I2C_STP_NOT_READY_ERROR; / Setup slave address I2caRegs.I2CSAR = msg->SlaveAddress; / Check if bus busy if (I2caRegs.I2CSTR.bit.BB = 1) return I2C_BUS_BUSY_ERROR; /判断总线空闲后进行数据发送/ / Setup number of bytes to send / MsgBuffer + Address I2caRegs.I2CCNT = msg->NumOfBytes+2; /递减 / Setup data to send I2caRegs.I