|
1 概述 MSP430F149的ADC12为SAR型12位AD,共有16路输入通道，其中8路独立的外部输入通道，2路接外部Vref+,Vref-，3路内部通道可分别测内部温度传感器、AVCC、和外部参考源。 P6口第二功能为AD输入端。MSP430F149的10、11分别接外部电压参考源正负极，7脚可将内部电压参考源输出。 ADC12共有18个中断源，公用一个中断向量ADC12_VECTOR。 AD的参考源可选择内部电压参考源或外部电压参考源。内部电压参考源有1.5V,2.5V可选，使用时向ADC12CTL0写入REFON+ REF2_5V就打开了2.5V。外部电压参考源由REF+接入。上电时若不设置参考源，则参考源为系统供电电压3.3V。 2 使用方法概述 2.1程序架构 中断方式 1、设置 ADC12工作模式，启动转换，开全局中断，等待中断 2、写中断处理函数 查询方式 设置ADC12工作模式，启动转换，查询中断标志ADC12IFG while (!(0x01 & ADC12IFG));转换完毕读取采样值，系统自动清除中断标志 2.2 使用概述 主要参数配置 设置工作方式：sing\\sequence\\re-sing\\re-sequencd; 设置转换时间：SHTX 设置触发方式：ADC12SC\\MSC\\TimerA\\ TimerB 设置通道：外部通道\\内部Temperature sensor 设置参考源：系统电压\\内部参考源\\外部参考源 其他细节配置 一般要配置采样转换模式为脉冲（SHP）,打开ADC12(ADC12ON),使能ADC12转换(ENC)，使能中断（如果采取中断模式），触发转换（若采用ADC12SC触发）。 解释 ADC12模数转换是在SHI的上升沿初始化的。SHI信号有四个来源： The ADC12SC bit；The Timer_A Output Unit 1； The Timer_B Output Unit 0； The Timer_B Output Unit 1。故单次采样时只需要每次设置ADC12CTL0 |= ADC12SC就采样一次；重复采样时，如Rep-sing，设置ADC12CTL1 = SHS_1 +CONSEQ_2就选择了Rep-sing模式，每次采样通过定时器A触发。 3 相关寄存器 1、ADC12CTL0 SHT1x Bits Sample-and-hold time. These bits define the number of ADC12CLK cycles in the sampling period for registers ADC12MEM8 to ADC12MEM15. SHT0x Bits Sample-and-hold time. These bits define the number of ADC12CLK cycles in the sampling period for registers ADC12MEM0 to ADC12MEM7. ADC12ON 0 ADC12 off 1 ADC12 on ENC ENC Bit 1 Enable conversion 0 ADC12 disabled 1 ADC12 enabled ADC12SC Bit 0 Start conversion. Software-controlled sample-and-conversion start. ADC12SC and ENC may be set together with one instruction. ADC12SC is reset automatically. 0 No sample-and-conversion-start 1 Start sample-and-conversion MSC Bit 7 Multiple sample and conversion. Valid only for sequence or repeated modes. 0 The sampling timer requires a rising edge of the SHI signal to trigger each sample-and-conversion. 1 The first rising edge of the SHI signal triggers the sampling timer, but further sample-and-conversions are performed automatically as soon as the prior conversion is completed. 2、ADC12CTL1 SHP SHP Bit 9 Sample-and-hold pulse-mode select. This bit selects the source of the sampling signal (SAMPCON) to be either the output of the sampling timer or the sample-input signal directly. 0 SAMPCON signal is sourced from the sample-input signal. 1 SAMPCON signal is sourced from the sampling timer. SHSx Bits 11-10 Sample-and-hold source select 00 ADC12SC bit 01 Timer_A.OUT1 10 Timer_B.OUT0 11 Timer_B.OUT1 CONSEQx Bits 2-1 Conversion sequence mode select 00 Single-channel, single-conversion 01 Sequence-of-channels 10 Repeat-single-channel 11 Repeat-sequence-of-channels 3、ADC12IE ADC12IEx Bits 15-0 Interrupt enable. These bits enable or disable the interrupt request for the ADC12IFGx bits. 0 Interrupt disabled 1 Interrupt enabled 4、ADC12IFG ADC12IFGx Bits 15-0 ADC12MEMx Interrupt flag. These bits are set when corresponding ADC12MEMx is loaded with a conversion result. The ADC12IFGx bits are reset if the corresponding ADC12MEMx is accessed, or may be reset with software. 0 No interrupt pending 1 Interrupt pending 5、ADC12MCTLX SREFx Bits 6-4 Select reference 000 VR+ = AVCC and VR− = AVSS 001 VR+ = VREF+ and VR− = AVSS 010 VR+ = VeREF+ and VR− = AVSS 011 VR+ = VeREF+ and VR− = AVSS 100 VR+ = AVCC and VR− = VREF−/ VeREF− 101 VR+ = VREF+ and VR− = VREF−/ VeREF− 110 VR+ = VeREF+ and VR− = VREF−/ VeREF− 111 VR+ = VeREF+ and VR− = VREF−/ VeREF− INCHx Bits 3-0 Input channel select 0000 A0 0001 A1 0010 A2 0011 A3 0100 A4 0101 A5 0110 A6 0111 A7 1000 VeREF+ 1001 VREF−/VeREF− 1010 Temperature sensor 1011 (AVCC – AVSS) / 2 1100 (AVCC – AVSS) / 2 1101 (AVCC – AVSS) / 2 1110 (AVCC – AVSS) / 2 1111 (AVCC – AVSS) / 2 EOS Bit 7 End of sequence. Indicates the last conversion in a sequence. 0 Not end of sequence 1 End of sequence 4实例 4.1 single采样，参考电源为系统电源 1.设置ADC12CTL0，使ADC12通道0采样保持时间为16 ADC12CLK(SHT0_2),开启ADC12模块（ADC12ON）； 2.设置ADC12CTL1，选择采样保持脉冲模式即SAMPCON为采样定时器（SHP） 3.设置ADC12IE,是通道0中断使能（0x01）; 4.设置ADC12CTL0,使能AD转换（ENC） 5.设置模拟信号输入IO口P60 7.设置ADC12CTL0，开启AD转换(ADC12SC),等待中断 8.中断中读取通道0转换值ADC12MEM0 ADC12CTL0 = SHT0_2 + ADC12ON; // Set sampling time, turn on ADC12 ADC12CTL1 = SHP; // Use sampling timer ADC12IE = 0x01; // Enable interrupt ADC12CTL0 |= ENC; // Conversion enabled P6SEL |= 0x01; // P6.0 ADC option select P2DIR |= 0x01; ADC12CTL0 |= ADC12SC; #pragma vector=ADC12_VECTOR __interrupt void ADC12_ISR (void) { if (ADC12MEM0 < 0x7FF) P2OUT = 0; // Clear P1.0 LED off else P2OUT = 0XFF; // Set P1.0 LED on __low_power_mode_off_on_exit(); // 与上面等价_BIC_SR_IRQ(CPUOFF); // Clear CPUOFF bit from 0(SR) } 4.2 single采样参考源为2.5V 在ADC12CTL0中设置参考源 在ADC12MCTL0中为通道0选择参考源 ADC12CTL0 = ADC12ON+SHT0_2+REFON+REF2_5V; // Turn on and set up ADC12 ADC12CTL1 = SHP; // Use sampling timer ADC12MCTL0 = SREF_1; // Vr+=Vref+ for ( i=0; i<0x3600; i++); // Delay for reference start-up ADC12CTL0 |= ENC; while (1) { ADC12CTL0 |= ADC12SC; // Start conversion while ((ADC12IFG & BIT0)==0); _NOP(); // SET BREAKPOINT HERE } 4.3 Repeat-single采样,模拟输入为内部Temperature sensor 设置ADC12CTL1，采样保持源为定时器A,脉冲保持模式，Repeat-single模式 ADC12CTL1 = SHS_1 + SHP + CONSEQ_2; // TA trig., rpt conv. 设置ADC12MCTL0，通道0参考源为内部REF,模拟输入通道0选择为Temperature sensor ADC12MCTL0 = SREF_1 + INCH_10; // Channel A10, Vref+ ADC12IE = 0x01; // Enable ADC12IFG.0 ADC12CTL0 = SHT0_8 + REF2_5V + REFON + ADC12ON + ENC; // Config ADC12 TACCTL1 = OUTMOD_4; // Toggle on EQU1 (TAR = 0) TACTL = TASSEL_2 + MC_2; // SMCLK, cont-mode while (!(0x01 & ADC12IFG)); // First conversion? FirstADCVal = ADC12MEM0; // Read out 1st ADC value _BIS_SR(LPM0_bits + GIE); // Enter LPM0 w/ interrupt #pragma vector=ADC12_VECTOR __interrupt void ADC12ISR (void) { if (ADC12MEM0 <= FirstADCVal + ADCDeltaOn) P1OUT &= ~0x01; // LED off else P1OUT |= 0x01; // LED on } 摄氏温度和温度传感器电压转换关系：0摄氏度对应986mv，1摄氏度温差对应1.97mv温差 // oF = ((x/4096)*1500mV)-923mV)*1/1.97mV = x*761/4096 - 468 // IntDegF = (ADC12MEM0 - 2519)* 761/4096 IntDegF = (temp - 2519) * 761; IntDegF = IntDegF / 4096; // oC = ((x/4096)*1500mV)-986mV)*1/3.55mV = x*423/4096 - 278 // IntDegC = (ADC12MEM0 - 2692)* 423/4096 IntDegC = (temp - 2692) * 423; IntDegC = IntDegC / 4096; 4.4 Repeat-sequence mode Sequence模式时可以设置多个采样通道。在最后一个通道加上EOS就表明的采样通道结束位置。中断允许只需要设置最后一个通道。 为了采样速率尽可能快，可设置MSC,此时当SHI上升沿触发第一次采样后，后面的采样在上一次采样结束后自动进行。 ADC12CTL0 = ADC12ON+MSC+SHT0_8; // Turn on ADC12, extend sampling time // to avoid overflow of results ADC12CTL1 = SHP+CONSEQ_3; // Use sampling timer, repeated sequence ADC12MCTL0 = INCH_0; // ref+=AVcc, channel = A0 ADC12MCTL1 = INCH_1; // ref+=AVcc, channel = A1 ADC12MCTL2 = INCH_2; // ref+=AVcc, channel = A2 ADC12MCTL3 = INCH_3+EOS; // ref+=AVcc, channel = A3, end seq. ADC12IE = 0x08; // Enable ADC12IFG.3 ADC12CTL0 |= ENC; // Enable conversions ADC12CTL0 |= ADC12SC; // Start conversion _BIS_SR(LPM0_bits + GIE); // Enter LPM0, Enable interrupts #pragma vector=ADC12_VECTOR __interrupt void ADC12ISR (void) { static unsigned int index = 0; A0results[index] = ADC12MEM0; // Move A0 results, IFG is cleared A1results[index] = ADC12MEM1; // Move A1 results, IFG is cleared A2results[index] = ADC12MEM2; // Move A2 results, IFG is cleared A3results[index] = ADC12MEM3; // Move A3 results, IFG is cleared index = (index+1)%Num_of_Results; // Increment results index, modulo; Set Breakpoint here }
| 
提升卡
变色卡
千斤顶
1/7 
京公网安备 11010802033920号
Copyright © 2005-2025 EEWORLD.com.cn, Inc. All rights reserved
