DSP学习笔记（1）——F28335基础知识
❤ 2019.3.6
今天开始学习DSP，over。
我用的版本是德州仪器的TMS320F28335，用的开发板是研旭的TMS320F28335至尊开发板，到底有多至尊我也不知道，不过看起来教材和资料挺全的。
〇 基础知识
● DSP的历史
略（自己看书百度去）
● 数字信号处理特点
● DSP主要特点
● TI的芯片系列
F28335系列属于C2000系列，在TI看来不属于DSP，属于MCU，但是我们就当成DSP学（？）
● C2000系列简介
● DSP系统开发
● 如何成为一个优秀的DSP工程师
（真的假的？）
● 教程总纲
〇 DSP开发环境介绍
● CCS介绍
● CCS安装
（略）
● 仿真器
○ CCS6如何连接仿真器（这个手册上面有）
1、建立target configuration file
2、输入名字
3、选择仿真器、芯片，然后点save
♣ 经常会在工程文件里生成一个target configuration 文件
❤ 2019.3.22
〇 DSP开发流程
○ CMD文件（配置文件）
指定DSP内部的硬件存储器的一些相关地址以及长度。
包含两部分：MEMORY以及SECTIONS
MEMORY：指定DSP内部的ram和flash的首地址以及长度
SECTIONS：指定程序组成部分对应内存的储存部分（MEMORY中设定的部分）。
〇 TMS320F28335介绍
〇 时钟与看门狗
● 内部时钟
❤ 2019.3.23
● 外设时钟
● 看门狗
● 时钟及看门狗寄存器（英文版System Control and Interrupts Reference Guide P34）（中文版见《手把手》P83）
♣ System Control and Interrupts Reference Guide：官方下载地址
● 关于看门狗及时钟的初始化例子
打开官方例程的时钟配置文件
观察系统时钟初始化函数
//---------------------------------------------------------------------------
// InitSysCtrl:
//---------------------------------------------------------------------------
// This function initializes the System Control registers to a known state.
// - Disables the watchdog
// - Set the PLLCR for proper SYSCLKOUT frequency
// - Set the pre-scaler for the high and low frequency peripheral clocks
// - Enable the clocks to the peripherals
void InitSysCtrl(void)
{
// Disable the watchdog
DisableDog();
// Initialize the PLL control: PLLCR and DIVSEL
// DSP28_PLLCR and DSP28_DIVSEL are defined in DSP2833x_Examples.h
InitPll(DSP28_PLLCR,DSP28_DIVSEL);
// Initialize the peripheral clocks
InitPeripheralClocks();
}○ 第一个
//---------------------------------------------------------------------------
// Example: DisableDog:
//---------------------------------------------------------------------------
// This function disables the watchdog timer.
void DisableDog(void)
{
EALLOW;
SysCtrlRegs.WDCR= 0x0068;
EDIS;
}可以看到0x0068，转换成二进制就是0000 0000 0110 1000，查看watchdog的寄存器说明（英文版System Control and Interrupts Reference Guide P54）（中文版见《手把手》P88），可以知道其意义。
如果需要启用watchdog，则用这个函数：
//---------------------------------------------------------------------------
// Example: ServiceDog:
//---------------------------------------------------------------------------
// This function resets the watchdog timer.
// Enable this function for using ServiceDog in the application
void ServiceDog(void)
{
EALLOW;
SysCtrlRegs.WDKEY = 0x0055;
SysCtrlRegs.WDKEY = 0x00AA;
EDIS;
}查看相应寄存器：
可以知道需要启用watchdog的话需要先后写入这两个值。
○ 下面是锁相环初始化
首先看一下两个参数
/*-----------------------------------------------------------------------------
Specify the PLL control register (PLLCR) and divide select (DIVSEL) value.
-----------------------------------------------------------------------------*/
//#define DSP28_DIVSEL 0 // Enable /4 for SYSCLKOUT
//#define DSP28_DIVSEL 1 // Disable /4 for SYSCKOUT
#define DSP28_DIVSEL 2 // Enable /2 for SYSCLKOUT
//#define DSP28_DIVSEL 3 // Enable /1 for SYSCLKOUT
#define DSP28_PLLCR 10
//#define DSP28_PLLCR 9
//#define DSP28_PLLCR 8
//#define DSP28_PLLCR 7
//#define DSP28_PLLCR 6
//#define DSP28_PLLCR 5
//#define DSP28_PLLCR 4
//#define DSP28_PLLCR 3
//#define DSP28_PLLCR 2
//#define DSP28_PLLCR 1
//#define DSP28_PLLCR 0 // PLL is bypassed in this mode
//----------------------------------------------------------------------------可以看出DSP28_PLLCR是倍频，DSP28_DIVSEL是分频，然后在看一下倍频与分频设置函数：
//---------------------------------------------------------------------------
// Example: InitPll:
//---------------------------------------------------------------------------
// This function initializes the PLLCR register.
void InitPll(Uint16 val, Uint16 divsel)
{
// Make sure the PLL is not running in limp mode
if (SysCtrlRegs.PLLSTS.bit.MCLKSTS != 0)
{
// Missing external clock has been detected
// Replace this line with a call to an appropriate
// SystemShutdown(); function.
asm(" ESTOP0");
}
// DIVSEL MUST be 0 before PLLCR can be changed from
// 0x0000. It is set to 0 by an external reset XRSn
// This puts us in 1/4
if (SysCtrlRegs.PLLSTS.bit.DIVSEL != 0)
{
EALLOW;
SysCtrlRegs.PLLSTS.bit.DIVSEL = 0;
EDIS;
}
// Change the PLLCR
if (SysCtrlRegs.PLLCR.bit.DIV != val)
{
EALLOW;
// Before setting PLLCR turn off missing clock detect logic
SysCtrlRegs.PLLSTS.bit.MCLKOFF = 1;
SysCtrlRegs.PLLCR.bit.DIV = val;
EDIS;
// Optional: Wait for PLL to lock.
// During this time the CPU will switch to OSCCLK/2 until
// the PLL is stable. Once the PLL is stable the CPU will
// switch to the new PLL value.
//
// This time-to-lock is monitored by a PLL lock counter.
//
// Code is not required to sit and wait for the PLL to lock.
// However, if the code does anything that is timing critical,
// and requires the correct clock be locked, then it is best to
// wait until this switching has completed.
// Wait for the PLL lock bit to be set.
// The watchdog should be disabled before this loop, or fed within
// the loop via ServiceDog().
// Uncomment to disable the watchdog
DisableDog();
while(SysCtrlRegs.PLLSTS.bit.PLLLOCKS != 1)
{
// Uncomment to service the watchdog
// ServiceDog();
}
EALLOW;
SysCtrlRegs.PLLSTS.bit.MCLKOFF = 0;
EDIS;
}
// If switching to 1/2
if((divsel == 1)||(divsel == 2))
{
EALLOW;
SysCtrlRegs.PLLSTS.bit.DIVSEL = divsel;
EDIS;
}
// If switching to 1/1
// * First go to 1/2 and let the power settle
// The time required will depend on the system, this is only an example
// * Then switch to 1/1
if(divsel == 3)
{
EALLOW;
SysCtrlRegs.PLLSTS.bit.DIVSEL = 2;
DELAY_US(50L);
SysCtrlRegs.PLLSTS.bit.DIVSEL = 3;
EDIS;
}
}有点乱，看不懂，但是ti贴心的（真的么?）画了个流程图：
这个流程图配合寄存器说明来看
稍微有点混乱，不过不需要看明白，反正用默认的就行，也就是10倍频，2分频，配合30M晶振，最后得到系统频率150M。
○ 初始化外设时钟
函数代码：
//--------------------------------------------------------------------------
// Example: InitPeripheralClocks:
//---------------------------------------------------------------------------
// This function initializes the clocks to the peripheral modules.
// First the high and low clock prescalers are set
// Second the clocks are enabled to each peripheral.
// To reduce power, leave clocks to unused peripherals disabled
//
// Note: If a peripherals clock is not enabled then you cannot
// read or write to the registers for that peripheral
void InitPeripheralClocks(void)
{
EALLOW;
// HISPCP/LOSPCP prescale register settings, normally it will be set to default values
SysCtrlRegs.HISPCP.all = 0x0001;
SysCtrlRegs.LOSPCP.all = 0x0002;
// XCLKOUT to SYSCLKOUT ratio. By default XCLKOUT = 1/4 SYSCLKOUT
// XTIMCLK = SYSCLKOUT/2
XintfRegs.XINTCNF2.bit.XTIMCLK = 1;
// XCLKOUT = XTIMCLK/2
XintfRegs.XINTCNF2.bit.CLKMODE = 1;
// Enable XCLKOUT
XintfRegs.XINTCNF2.bit.CLKOFF = 0;
// Peripheral clock enables set for the selected peripherals.
// If you are not using a peripheral leave the clock off
// to save on power.
//
// Note: not all peripherals are available on all 2833x derivates.
// Refer to the datasheet for your particular device.
//
// This function is not written to be an example of efficient code.
SysCtrlRegs.PCLKCR0.bit.ADCENCLK = 1; // ADC
// *IMPORTANT*
// The ADC_cal function, which copies the ADC calibration values from TI reserved
// OTP into the ADCREFSEL and ADCOFFTRIM registers, occurs automatically in the
// Boot ROM. If the boot ROM code is bypassed during the debug process, the
// following function MUST be called for the ADC to function according
// to specification. The clocks to the ADC MUST be enabled before calling this
// function.
// See the device data manual and/or the ADC Reference
// Manual for more information.
ADC_cal();
SysCtrlRegs.PCLKCR0.bit.I2CAENCLK = 1; // I2C
SysCtrlRegs.PCLKCR0.bit.SCIAENCLK = 1; // SCI-A
SysCtrlRegs.PCLKCR0.bit.SCIBENCLK = 1; // SCI-B
SysCtrlRegs.PCLKCR0.bit.SCICENCLK = 1; // SCI-C
SysCtrlRegs.PCLKCR0.bit.SPIAENCLK = 1; // SPI-A
SysCtrlRegs.PCLKCR0.bit.MCBSPAENCLK = 1; // McBSP-A
SysCtrlRegs.PCLKCR0.bit.MCBSPBENCLK = 1; // McBSP-B
SysCtrlRegs.PCLKCR0.bit.ECANAENCLK=1; // eCAN-A
SysCtrlRegs.PCLKCR0.bit.ECANBENCLK=1; // eCAN-B
SysCtrlRegs.PCLKCR0.bit.TBCLKSYNC = 0; // Disable TBCLK within the ePWM
SysCtrlRegs.PCLKCR1.bit.EPWM1ENCLK = 1; // ePWM1
SysCtrlRegs.PCLKCR1.bit.EPWM2ENCLK = 1; // ePWM2
SysCtrlRegs.PCLKCR1.bit.EPWM3ENCLK = 1; // ePWM3
SysCtrlRegs.PCLKCR1.bit.EPWM4ENCLK = 1; // ePWM4
SysCtrlRegs.PCLKCR1.bit.EPWM5ENCLK = 1; // ePWM5
SysCtrlRegs.PCLKCR1.bit.EPWM6ENCLK = 1; // ePWM6
SysCtrlRegs.PCLKCR0.bit.TBCLKSYNC = 1; // Enable TBCLK within the ePWM
SysCtrlRegs.PCLKCR1.bit.ECAP3ENCLK = 1; // eCAP3
SysCtrlRegs.PCLKCR1.bit.ECAP4ENCLK = 1; // eCAP4
SysCtrlRegs.PCLKCR1.bit.ECAP5ENCLK = 1; // eCAP5
SysCtrlRegs.PCLKCR1.bit.ECAP6ENCLK = 1; // eCAP6
SysCtrlRegs.PCLKCR1.bit.ECAP1ENCLK = 1; // eCAP1
SysCtrlRegs.PCLKCR1.bit.ECAP2ENCLK = 1; // eCAP2
SysCtrlRegs.PCLKCR1.bit.EQEP1ENCLK = 1; // eQEP1
SysCtrlRegs.PCLKCR1.bit.EQEP2ENCLK = 1; // eQEP2
SysCtrlRegs.PCLKCR3.bit.CPUTIMER0ENCLK = 1; // CPU Timer 0
SysCtrlRegs.PCLKCR3.bit.CPUTIMER1ENCLK = 1; // CPU Timer 1
SysCtrlRegs.PCLKCR3.bit.CPUTIMER2ENCLK = 1; // CPU Timer 2
SysCtrlRegs.PCLKCR3.bit.DMAENCLK = 1; // DMA Clock
SysCtrlRegs.PCLKCR3.bit.XINTFENCLK = 1; // XTIMCLK
SysCtrlRegs.PCLKCR3.bit.GPIOINENCLK = 1; // GPIO input clock
EDIS;
}♣ 首先注意的是EALLOW和EDIS语句，关于这两个语句，我找到了一篇介绍：
原文地址：DSP的EALLOW和EDIS指令
先看这段：
我们先找到对应的寄存器说明：
由上可知，这两句的意思是将高速时钟配置为2分频，将低速时钟配置为4分频。
这个是用来控制时钟输出的，可以将时钟供给其他模块，可以省一个晶振（？）
这个是用来控制外设时钟的开关，需要哪个模块就开哪个时钟，不用就关上，可以省电。
