TI MSPM0L1306 LaunchPad体验05：使用ADC采集热敏电阻信号并换算成温度

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TI MSPM0L1306 LaunchPad体验05：使用ADC采集热敏电阻信号并换算成温度 [复制链接]

 

电路分析

LaunchPad板载的热敏电阻是10k的线性热敏电阻（PTC），与10k的定值电阻串联分压。室温下输出电压大约是1.6V。通过J1跳线可以直接输出到MSPM0L1306的PA. 15。

软件设计

使用adc_to_uart模板，可以将adc转换结果输出到串口。

 

使用SysConfig工具，将ADC12的输入通道设定为Channel 9，界面上会自动提示Pin为PA15。

 

也可以点击界面右上角的Device View，直接查看Pin的分配情况。

 

改用printf()函数发送数据：

将ADC值转换为温度的代码可以直接从OOBE中摘录，或者参考热敏电阻的文档。

程序运行结果：

用手指放在热敏电阻附近的PCB上，捂热一会后，温度明显上升。

 

版图设计

热敏电阻（RT1）在开发板下部中间位置。可以看到PCB此处有镂空的狭缝设计，将热敏电阻放置在“孤岛”上。这样做可以将PCB其余部分的发热对温度测量影响降低到最低，从而使热敏电阻可以更准确地测量环境温度。

小结

得益于合适的样例程序和SysConfig，对MSPM0的ADC、UART等外设编程十分容易。这样我们就不需要手写大量繁琐的配置代码，也不需要反复查阅参考手册，只需要专注于业务逻辑即可。

 

 

完整代码

C程序

#include "stdio.h"
#include <math.h>
#include "ti_msp_dl_config.h"
volatile bool gCheckADC;
volatile uint16_t gADCResult;
volatile float temperature;

float VBias = 3.30; // set the VBIAS voltage
// set the number of bits based on you ADC (2^# of ADC Bit Value)
unsigned int ADC_BITS = 4096;
float VTEMP = 0;     // set up the variable for the measured voltage
float THRM_TEMP = 0; // setup the variable for the calculated temperature

float thermistor_calc_temperature(uint16_t raw_ADC) {
  // THRM calculations via regression
  // Copied from TI Thermistor Design Tool Excel Doc
  float VTEMP = 0.0;
  float THRM_ADC = raw_ADC;

  float THRM_A0 = -4.232811E+02;
  float THRM_A1 = 4.728797E+02;
  float THRM_A2 = -1.988841E+02;
  float THRM_A3 = 4.869521E+01;
  float THRM_A4 = -1.158754E+00;

  VTEMP = (VBias / ADC_BITS) * THRM_ADC; // calculate volts per bit then
                                         // multiply that times the ADV value
  THRM_TEMP = (THRM_A4 * powf(VTEMP, 4)) + (THRM_A3 * powf(VTEMP, 3)) +
              (THRM_A2 * powf(VTEMP, 2)) + (THRM_A1 * VTEMP) +
              THRM_A0; // 4th order regression to get temperature
  return THRM_TEMP;
}

int main(void) {
  SYSCFG_DL_init();

  NVIC_EnableIRQ(ADC12_0_INST_INT_IRQN);
  gCheckADC = false;

  while (1) {
    DL_ADC12_startConversion(ADC12_0_INST);

    while (false == gCheckADC) {
      __WFE();
    }

    /*
     *  UART is 8 bits and the ADC result is 16 bits
     *  Split the ADC result into 2 then send via UART.
     */
    gADCResult = DL_ADC12_getMemResult(ADC12_0_INST, DL_ADC12_MEM_IDX_0);
    // uint8_t lowbyte  = (uint8_t)(gADCResult & 0xFF);
    // uint8_t highbyte = (uint8_t)((gADCResult >> 8) & 0xFF);

    temperature = thermistor_calc_temperature(gADCResult);
    printf("ADC=%d, temperature=%f\n", gADCResult, temperature);
    // DL_UART_Main_transmitData(UART_0_INST, highbyte);
    // DL_UART_Main_transmitData(UART_0_INST, lowbyte);

    gCheckADC = false;
    DL_ADC12_enableConversions(ADC12_0_INST);
  }
}

void ADC12_0_INST_IRQHandler(void) {
  switch (DL_ADC12_getPendingInterrupt(ADC12_0_INST)) {
  case DL_ADC12_IIDX_MEM0_RESULT_LOADED:
    gCheckADC = true;
    break;
  default:
    break;
  }
}

SysConfig参考代码

**
 * These arguments were used when this file was generated. They will be automatically applied on subsequent loads
 * via the GUI or CLI. Run CLI with '--help' for additional information on how to override these arguments.
 * @cliArgs --device "MSPM0L130X" --package "VQFN-32(RHB)" --part "Default" --product "mspm0_sdk@1.20.00.06"
 * @versions  {"tool":"1.18.0+3266"}
 */

/**
 * Import the modules used in this configuration.
 */
const ADC12  = scripting.addModule("/ti/driverlib/ADC12", {}, false);
const ADC121 = ADC12.addInstance();
const Board  = scripting.addModule("/ti/driverlib/Board");
const SYSCTL = scripting.addModule("/ti/driverlib/SYSCTL");
const UART   = scripting.addModule("/ti/driverlib/UART", {}, false);
const UART1  = UART.addInstance();

/**
 * Write custom configuration values to the imported modules.
 */
ADC121.$name               = "ADC12_0";
ADC121.enabledInterrupts   = ["DL_ADC12_INTERRUPT_MEM0_RESULT_LOADED"];
ADC121.sampleTime0         = "125 us";
ADC121.sampClkSrc          = "DL_ADC12_CLOCK_ULPCLK";
ADC121.sampClkDiv          = "DL_ADC12_CLOCK_DIVIDE_8";
ADC121.adcMem0chansel      = "DL_ADC12_INPUT_CHAN_9";
ADC121.peripheral.$assign  = "ADC0";
ADC121.adcPin9Config.$name = "ti_driverlib_gpio_GPIOPinGeneric0";



UART1.$name                    = "UART_0";
UART1.enableFIFO               = true;
UART1.direction                = "TX";
UART1.rxFifoThreshold          = "DL_UART_RX_FIFO_LEVEL_ONE_ENTRY";
UART1.targetBaudRate           = 115200;
UART1.peripheral.$assign       = "UART0";
UART1.peripheral.txPin.$assign = "PA8";
UART1.txPinConfig.$name        = "ti_driverlib_gpio_GPIOPinGeneric1";

/**
 * Pinmux solution for unlocked pins/peripherals. This ensures that minor changes to the automatic solver in a future
 * version of the tool will not impact the pinmux you originally saw.  These lines can be completely deleted in order to
 * re-solve from scratch.
 */
ADC121.peripheral.adcPin9.$suggestSolution = "PA15";
Board.peripheral.$suggestSolution          = "DEBUGSS";
Board.peripheral.swclkPin.$suggestSolution = "PA20";
Board.peripheral.swdioPin.$suggestSolution = "PA19";
SYSCTL.peripheral.$suggestSolution         = "SYSCTL";