基于MSP430简易示波器的设计讲解

基于MSP430简易示波器的设计
自动化1107
王诗雨
2013.12
1.硬件设计
1.1 单片机
选用MSP430G2553单片机，该单片机具有低功耗的特点，内部自带8路10位AD转换器（ADC10），最高主频可达16Mhz，对于一个简易示波器来说这些特点足够我们使用。

1.2 程控放大电路
程控放大电路的作用是对大信号进行衰减，对小信号进行放大，保证输入到A／D转换器的信号幅度在要求的输入电压范围内，以达到最好的测量与观察效果。

采用模拟开关CD4051，配合精密电位器实现多挡垂直分辨率。

在MSP430单片机中使用寄存器模块设置通道号，通过写入通道号控制模拟开关选通不同的反馈电阻，从而实现不同的放大倍数，对信号进行不同程度的放大（衰减）。

电路图如下:
1.3 简易调理电路
由于示波器观察信号大多是正负电压信号，考虑到ADC10一般使用的是单极性参考电压（也可以使用寄存器设置双极性参考电压，这样就不需要调理电路了，但最好加一级缓冲）。

为了采样到信号的负电压，就需要给该信号叠加直流量，将负电压部分信号抬高至零电平以上，因此采用信号调理电路。

电路图如下：
1.4 LCD显示电路和按键电路
利用LCD的SPI通信模式与MSP430单片机连接，这样可以得到不错的通信速度，并且可以尽可能的减少MSP430引脚的占用，具体电路这里就不给出了。

（按照spi连接）
利用简单独立按键实现放大倍数调节，采样频率设置等功能即可。

2.软件设计
2.1 单片机初始化
对P2口初始化，打开P2口的中断；将通信方式设置为硬件spi通信模式（注意spi通信在上升沿还是在下降沿开始）。

WDTCTL=WDTPW+WDTHOLD; //关看门狗
P1OUT = 0x00; // P1 setup for LED & reset output
P1DIR |= BIT0 + BIT2 + BIT3 + BIT4 + BIT5;
P1SEL = BIT1 + BIT2 + BIT4;
P1SEL2 = BIT1 + BIT2 + BIT4;
P2REN |= 0x38;
P2DIR = 0x07;
P2OUT = 0;
P2IE |= 0x38; // P1.4 interrupt enabled
P2IFG &= ~0x38;
will=0;
UCA0CTL0 |= UCCKPL + UCMSB + UCMST + UCSYNC + UCCKPH ; // 3-pin, 8-bit SPI master
UCA0CTL1 |= UCSSEL_2; // SMCLK
UCA0BR0 |= 0x04; // /2
UCA0BR1 = 0; //
UCA0MCTL = 0; // No modulation
UCA0CTL1 &= ~UCSWRST; // **Initialize USCI state machine**
P1OUT &= ~BIT5; // Now with SPI signals initialized,
P1OUT |= BIT5; // reset slave
ADC10初始化，开启参考源和中断。

ADC10CTL0 = ADC10SHT_0 + REFON + ADC10ON + ADC10IE;
ADC10CTL1 = INCH_6;
ADC10AE0 |= 0x40;
显示初始化，对LCD的界面显示初始化。

Initial_ILI9340C();
Delay_ms(300);
LCD_TEST_SingleColor(Black);
LCD_TEST_SingleColor(Black);
LCD_TEST_PartColor(Blue);
for(wh=22; wh<220 ;wh+=10)
{
LCD_draw_Line(wh,39,White);
LCD_draw_Line(wh,79,White);
LCD_draw_Line(wh,119,White);
LCD_draw_Line(wh,159,White);
LCD_draw_Line(wh,199,White);
LCD_draw_Line(wh,239,White);
LCD_draw_Line(wh,279,White);
}
Delay_ms(100);
for(co=2; co<320 ;co+=10)
{
LCD_draw_Col(69,co,White);
LCD_draw_Col(119,co,White);
LCD_draw_Col(169,co,White);
}
Delay_ms(100);
2.2 程控选择程序
根据按键的次数，在P2口中断改变will的值，并通过P2口输出给CD4051的ABC开关选择端，对放大倍数进行选择。

#pragma vector=PORT2_VECTOR
__interrupt void Port_2(void)
{
if(P2IFG & 0x10)
{
while(0x10 & P2IN);
will++;
if(will==8)
{
will=7;
}
}
if(P2IFG & 0x20)
{
while(0x20 & P2IN);
will--;
if(will==255)
{
will=0;
}
}
if(P2IFG & 0x08)
{
while(0x08 & P2IN);
chan++;
if(chan==4)
chan=0;
}
P2IFG &= ~0x38;
P2OUT=will;
}
2.3 采样频率设置
通过改变ADC10CTL1，通过按键次数对应值不同改变ADC10时钟的频率来调节电路的采样频率。

switch(chan)
{
case 0: ADC10CTL1 = INCH_6; break;
case 1: ADC10CTL1 |= ADC10DIV0 + ADC10DIV1; break;
case 2: ADC10CTL1 |= ADC10DIV0 + ADC10DIV2; break;
case 3: ADC10CTL1 |= ADC10DIV0 + ADC10DIV1 + ADC10DIV2;
break;
}
2.4 软件触发程序
只有在一定条件下才使lcd刷新，保证每次采集到的波形都从一点开始显示，防止由于每次采集到的点不同导致波形一直移动。

ADC10CTL0 |= ENC + ADC10SC;
// Sampling and conversion start
__bis_SR_register(CPUOFF + GIE);
if(cir==0) key1 = ADC10MEM/5;
if(cir==1) key2 = ADC10MEM/5;
if(cir==2) key3 = ADC10MEM/5;
if(cir>2 && key1>key2 && key2>key3) //((key1-100)/2)>=(key2-100)
{
temp[0]=key1;
temp[1]=key2;
temp[2]=key3;
temp[cir]=ADC10MEM/5;
}
ADC10CTL0 &= ~ENC;
2.5 显示刷新程序
示波器是一个动态显示过程，因此在过程中可能会引起初始界面被部分覆盖，以此需要定时刷新初始界面。

trig++;
if(trig%20==0)
{
for(wh=22; wh<220 ;wh+=10)
{
LCD_draw_Line(wh,39,White);
LCD_draw_Line(wh,79,White);
LCD_draw_Line(wh,119,White);
LCD_draw_Line(wh,159,White);
LCD_draw_Line(wh,199,White);
LCD_draw_Line(wh,239,White);
LCD_draw_Line(wh,279,White); }
Delay_ms(300);
for(co=2; co<320 ;co+=10)
{
LCD_draw_Col(69,co,White);
LCD_draw_Col(119,co,White);
LCD_draw_Col(169,co,White); }
Delay_ms(300);
}
附：源程序
#include"msp430g2553.h"//STC12单片机头文件
//颜色定义
#define Blue 0x001f
#define Yellow 0xffe0
#define Green 0x07e0
#define Black 0x0000
#define White 0xffff
#define Red 0xf800
//引脚定义
#define R_ESET1 P1OUT|=BIT5; //液晶RESET引脚,接单片机IO引脚
#define R_ESET0 P1OUT&=~BIT5;
#define C_D1 P1OUT|=BIT3;//液晶D/CX引脚，数据/命令控制，接单片机IO引脚
#define C_D0 P1OUT&=~BIT3;
#define C_S1 P1OUT|=BIT0;//液晶片选CS,P1.4为单片机SPI总线的SS引脚,通过MSTR位配置为IO模式
#define C_S0 P1OUT&=~BIT0;
unsigned char MST_Data, SLV_Data, wh, temp[320], trig=0, key1, key2 ,key3 ,will ,chan=0;
unsigned int co,cir;
void delay(void)
{
unsigned int j;
for(j=100;j>0;j--);
}
void Delay_us(int value)////延时函数_us
{
while (value)
value--;
}
void Delay_ms(int value)////延时函数_ms
{
while (value){
Delay_us(999);
value--;
}
}
void LCD_Writ_Bus(char a){ //数据写入函数 8位
C_S0;
UCA0TXBUF = a;
__delay_cycles(50);
while (!(IFG2 & UCA0TXIFG));
C_S1;
}
void LCD_WRITE_CMD(char cmd){//8 bit
C_D0;
LCD_Writ_Bus(cmd);
}
void LCD_WRITE_COM_DATA(char com_data){//8 bit
C_D1;
LCD_Writ_Bus(com_data);
}
void LCD_WRITE_DATA(int a){//16位数据,分两次，每次送8位
C_D1;
LCD_Writ_Bus(a>>8);
LCD_Writ_Bus(a);
}
//设置绘点窗口，x=0~239,y=0~319
void Address_set(unsigned int x1,unsigned int x2,unsigned int y1,unsigned int y2)
{
LCD_WRITE_CMD(0x2a); //x轴
LCD_WRITE_DATA(x1);
LCD_WRITE_DATA(x2);
LCD_WRITE_CMD(0x2b); //y轴
LCD_WRITE_DATA(y1);
LCD_WRITE_DATA(y2);
LCD_WRITE_CMD(0x2c);
}
void LCD_TEST_SingleColor(int Discolor){
int i,j;
Address_set(0,239,0,319);
for (i=0;i<320;i++){
for (j=0;j<240;j++){
LCD_WRITE_DATA(Discolor);
}
}
}
void LCD_TEST_PartColor(int Discolor){
int i,j;
Address_set(0,19,0,319);
for (i=0;i<320;i++){
for (j=0;j<20;j++){
LCD_WRITE_DATA(Discolor);
}
}
Address_set(220,239,0,319);
for (i=0;i<320;i++){
for (j=220;j<240;j++){
LCD_WRITE_DATA(Discolor);
}
}
}
//画一条横线
void LCD_draw_Line(unsigned int x,unsigned int y,unsigned int color) { int i;
Address_set(x,x+4,y,y);
for (i=0;i<5;i++){
LCD_WRITE_DATA(color);
}
}
void LCD_draw_Col(unsigned int x,unsigned int y,unsigned int color) { int i;
Address_set(x,x,y,y+4);
for (i=0;i<5;i++){
LCD_WRITE_DATA(color);
}
}
//液晶主控初始化
void Initial_ILI9340C(void)
{
LCD_WRITE_CMD(0xCB);
LCD_WRITE_COM_DATA(0x39);
LCD_WRITE_COM_DATA(0x2C);
LCD_WRITE_COM_DATA(0x00);
LCD_WRITE_COM_DATA(0x34);
LCD_WRITE_COM_DATA(0x02);
LCD_WRITE_CMD(0xCF);
LCD_WRITE_COM_DATA(0x00);
LCD_WRITE_COM_DATA(0XC1);
LCD_WRITE_COM_DATA(0X30);
LCD_WRITE_CMD(0xE8);
LCD_WRITE_COM_DATA(0x85);
LCD_WRITE_COM_DATA(0x00);
LCD_WRITE_COM_DATA(0x78);
LCD_WRITE_CMD(0xEA);
LCD_WRITE_COM_DATA(0x00);
LCD_WRITE_COM_DATA(0x00);
LCD_WRITE_CMD(0xED);
LCD_WRITE_COM_DATA(0x64);
LCD_WRITE_COM_DATA(0x03);
LCD_WRITE_COM_DATA(0X12);
LCD_WRITE_COM_DATA(0X81);
LCD_WRITE_CMD(0xF7);
LCD_WRITE_COM_DATA(0x20);
LCD_WRITE_CMD(0xC0); //Power control
LCD_WRITE_COM_DATA(0x23); //VRH[5:0]
LCD_WRITE_CMD(0xC1); //Power control
LCD_WRITE_COM_DATA(0x10); //SAP[2:0];BT[3:0]
LCD_WRITE_CMD(0xC5); //VCM control
LCD_WRITE_COM_DATA(0x3e); //对比度调节
LCD_WRITE_COM_DATA(0x28);
LCD_WRITE_CMD(0xC7); //VCM control2
LCD_WRITE_COM_DATA(0x86); //--
LCD_WRITE_CMD(0x36); // Memory Access Control
LCD_WRITE_COM_DATA(0xC8);
LCD_WRITE_CMD(0x3A);
LCD_WRITE_COM_DATA(0x55);
LCD_WRITE_CMD(0xB1);
LCD_WRITE_COM_DATA(0x00);
LCD_WRITE_COM_DATA(0x18);
LCD_WRITE_CMD(0xB6); // Display Function Control LCD_WRITE_COM_DATA(0x08);
LCD_WRITE_COM_DATA(0x82);
LCD_WRITE_COM_DATA(0x27);
LCD_WRITE_CMD(0xF2); // 3Gamma Function Disable LCD_WRITE_COM_DATA(0x00);
LCD_WRITE_CMD(0x26); //Gamma curve selected
LCD_WRITE_COM_DATA(0x01);
LCD_WRITE_CMD(0xE0); //Set Gamma
LCD_WRITE_COM_DATA(0x0F);
LCD_WRITE_COM_DATA(0x31);
LCD_WRITE_COM_DATA(0x2B);
LCD_WRITE_COM_DATA(0x0C);
LCD_WRITE_COM_DATA(0x0E);
LCD_WRITE_COM_DATA(0x08);
LCD_WRITE_COM_DATA(0x4E);
LCD_WRITE_COM_DATA(0xF1);
LCD_WRITE_COM_DATA(0x37);
LCD_WRITE_COM_DATA(0x07);
LCD_WRITE_COM_DATA(0x10);
LCD_WRITE_COM_DATA(0x03);
LCD_WRITE_COM_DATA(0x0E);
LCD_WRITE_COM_DATA(0x09);
LCD_WRITE_COM_DATA(0x00);
LCD_WRITE_CMD(0XE1); //Set Gamma
LCD_WRITE_COM_DATA(0x00);
LCD_WRITE_COM_DATA(0x0E);
LCD_WRITE_COM_DATA(0x14);
LCD_WRITE_COM_DATA(0x03);
LCD_WRITE_COM_DATA(0x11);
LCD_WRITE_COM_DATA(0x07);
LCD_WRITE_COM_DATA(0x31);
LCD_WRITE_COM_DATA(0xC1);
LCD_WRITE_COM_DATA(0x48);
LCD_WRITE_COM_DATA(0x08);
LCD_WRITE_COM_DATA(0x0F);
LCD_WRITE_COM_DATA(0x0C);
LCD_WRITE_COM_DATA(0x31);
LCD_WRITE_COM_DATA(0x36);
LCD_WRITE_COM_DATA(0x0F);
LCD_WRITE_CMD(0x11); //Exit Sleep
Delay_ms(120);
LCD_WRITE_CMD(0x29); //Display on
LCD_WRITE_CMD(0x2c);
}
//LCD进入休眠状态
void LCD_Sleep_ILI9340C(void)
{
LCD_WRITE_CMD(0x28);//Display off
Delay_ms(20);
LCD_WRITE_CMD(0x10);//Enter Sleep mode
}
//LCD退出休眠状态
void LCD_ExitSleep_ILI9340C(void)
{
LCD_WRITE_CMD(0x11);//Exit Sleep
Delay_ms(120);
LCD_WRITE_CMD(0x29);//Display on
LCD_WRITE_CMD(0x2c);
}
void main()
{
WDTCTL=WDTPW+WDTHOLD; //关看门狗
P1OUT = 0x00; // P1 setup for LED & reset output
P1DIR |= BIT0 + BIT2 + BIT3 + BIT4 + BIT5;
P1SEL = BIT1 + BIT2 + BIT4;
P1SEL2 = BIT1 + BIT2 + BIT4;
P2REN |= 0x38;
P2DIR = 0x07;
P2OUT = 0;
P2IE |= 0x38; // P1.4 interrupt enabled P2IFG &= ~0x38;
will=0;
UCA0CTL0 |= UCCKPL + UCMSB + UCMST + UCSYNC + UCCKPH ; // 3-pin, 8-bit SPI master
UCA0CTL1 |= UCSSEL_2; // SMCLK
UCA0BR0 |= 0x04; // /2
UCA0BR1 = 0; //
UCA0MCTL = 0; // No modulation
UCA0CTL1 &= ~UCSWRST; // **Initialize USCI state machine**
P1OUT &= ~BIT5; // Now with SPI signals initialized,
P1OUT |= BIT5; // reset slave
__delay_cycles(75); // Wait for slave to initialize
Initial_ILI9340C();
Delay_ms(300);
LCD_TEST_SingleColor(Black);
LCD_TEST_SingleColor(Black);
LCD_TEST_PartColor(Blue);
for(wh=22; wh<220 ;wh+=10)
{
LCD_draw_Line(wh,39,White);
LCD_draw_Line(wh,79,White);
LCD_draw_Line(wh,119,White);
LCD_draw_Line(wh,159,White);
LCD_draw_Line(wh,199,White);
LCD_draw_Line(wh,239,White);
LCD_draw_Line(wh,279,White);
}
Delay_ms(100);
for(co=2; co<320 ;co+=10)
{
LCD_draw_Col(69,co,White);
LCD_draw_Col(119,co,White);
LCD_draw_Col(169,co,White);
}
Delay_ms(100);
ADC10CTL0 = ADC10SHT_0 + REFON + ADC10ON + ADC10IE;
ADC10CTL1 = INCH_6;
ADC10AE0 |= 0x40; // PA.1 ADC option select
while(1)
{
for(cir=0;cir<320;cir++)
{
ADC10CTL0 |= ENC + ADC10SC; // Sampling and conversion start
__bis_SR_register(CPUOFF + GIE); // LPM0, ADC10_ISR will force exi
if(cir==0) key1 = ADC10MEM/5;
if(cir==1) key2 = ADC10MEM/5;
if(cir==2) key3 = ADC10MEM/5;
if(cir>2 && key1>key2 && key2>key3) //((key1-100)/2)>=(key2-100)
{
temp[0]=key1;
temp[1]=key2;
temp[2]=key3;
temp[cir]=ADC10MEM/5;
}
ADC10CTL0 &= ~ENC;
switch(chan)
{
case 0: ADC10CTL1 = INCH_6; break;
case 1: ADC10CTL1 |= ADC10DIV0 + ADC10DIV1; break;
case 2: ADC10CTL1 |= ADC10DIV0 + ADC10DIV2; break;
case 3: ADC10CTL1 |= ADC10DIV0 + ADC10DIV1 + ADC10DIV2; break;
}
}
for(cir=0;cir<320;cir++)
{
Address_set(20+temp[cir],20+temp[cir],cir,cir);
LCD_WRITE_DATA(Yellow);
}
Delay_ms(300);
for(cir=0;cir<320;cir++)
{
Address_set(20+temp[cir],20+temp[cir],cir,cir);
LCD_WRITE_DATA(Yellow);
}
Delay_ms(300);
for(cir=0;cir<320;cir++)
{
Address_set(20+temp[cir],20+temp[cir],cir,cir);
LCD_WRITE_DATA(Yellow);
}
Delay_ms(300);
for(cir=0;cir<320;cir++)
{
Address_set(20+temp[cir],20+temp[cir],cir,cir);
LCD_WRITE_DATA(Yellow);
}
Delay_ms(300);
for(cir=0;cir<320;cir++)
{
Address_set(20+temp[cir],20+temp[cir],cir,cir);
LCD_WRITE_DATA(Black);
}
trig++;
if(trig%20==0)
{
for(wh=22; wh<220 ;wh+=10)
{
LCD_draw_Line(wh,39,White);
LCD_draw_Line(wh,79,White);
LCD_draw_Line(wh,119,White);
LCD_draw_Line(wh,159,White);
LCD_draw_Line(wh,199,White);
LCD_draw_Line(wh,239,White);
LCD_draw_Line(wh,279,White);
}
Delay_ms(300);
for(co=2; co<320 ;co+=10)
{
LCD_draw_Col(69,co,White);
LCD_draw_Col(119,co,White);
LCD_draw_Col(169,co,White);
}
Delay_ms(300);
}
}
}
// ADC10 interrupt service routine
#pragma vector=ADC10_VECTOR
__interrupt void ADC10_ISR (void)
{
__bic_SR_register_on_exit(CPUOFF); // Clear CPUOFF bit from 0(SR)
}
#pragma vector=PORT2_VECTOR
__interrupt void Port_2(void)
{
if(P2IFG & 0x10)
{
while(0x10 & P2IN);
will++;
if(will==8)
{
will=7;
}
}
if(P2IFG & 0x20)
{
while(0x20 & P2IN);
will--;
if(will==255)
{
will=0;
}
}
if(P2IFG & 0x08)
{
while(0x08 & P2IN);
chan++;
if(chan==4)
chan=0;
}
P2IFG &= ~0x38;
P2OUT=will;
}。