我正在努力让 ADC 与我的设备一起工作。我正在使用 dsPIC33FJ128GP802 并尝试通过手动采样和转换来缓慢启动。
我的代码发布在下面，我已经为 ADC 设置了每个寄存器，然后尝试仅采样一次以从我连接的传感器获取电压。我应该看到的值大约是 0.7V，但我得到的是 -17408（10111100 00000000）区域。这可以上升到 -2000 左右，但该值首先不应为负。
#include <p33Fxxxx.h>
_FOSCSEL(FNOSC_FRCPLL) // select internal 7.37MHz osc with PPL
_FOSC(OSCIOFNC_OFF & POSCMD_XT) // no clock output, external OSC disabled
_FWDT(FWDTEN_OFF) // disable the watchdog timer
_FPOR(FPWRT_PWR1) // Turn off the power-up timers.
int ADCValue;
void DELAY(unsigned ms) {
unsigned j;
unsigned i;
for (j = 0; j < ms; j++) {
for (i = 0; i < 0x1F40; i++);
}
}
int main(void) {
// set up clock to 80MHz
PLLFBD = 41; // sets M = 41+2 = 43
CLKDIVbits.PLLPRE = 0; // sets N1 = 2
CLKDIVbits.PLLPOST = 0; // sets N2 = 2
while (!OSCCONbits.LOCK); // wait for PLL ready
AD1CON1 = 0; // set everything to zero to start with.
AD1CON1bits.ADON = 0; // turn ADC off.
AD1CON1bits.ADSIDL = 0; // continue module operation in idle mode.
AD1CON1bits.ADDMABM = 1; // DMA buffers are written in the order of conversion.
AD1CON1bits.AD12B = 0; // set to 10bit mode.
AD1CON1bits.FORM = 3; // set data output to signed fractional.
AD1CON1bits.SSRC = 0; // manual conversion. clearing sample bit manually.
AD1CON1bits.SIMSAM = 1; // collect samples from channels 0, 1, 2, 3 simultaneously.
AD1CON1bits.ASAM = 0; // manual sample. samples when SAMP bit is set.
AD1CON1bits.SAMP = 0; // sample enable bit.
AD1CON1bits.DONE = 0; // ADC conversion status bit.
AD1CON2 = 0; // set everything to zero to start with.
AD1CON2bits.VCFG = 0; // converter voltage ref. set to AVdd and AVss.
AD1CON2bits.CSCNA = 0; // input scan select bit. set to do not scan.
AD1CON2bits.CHPS = 0; // channel select bits. set to just channel 0;
AD1CON2bits.BUFS = 0; // buffer fill status (invalid as BUFM is 0);
AD1CON2bits.SMPI = 0; // ADC interrupt is generated after every sample/conversion.
AD1CON2bits.BUFM = 0; // buffer fill mode. set to always start filling from start address.
AD1CON2bits.ALTS = 0; // Alternate input sample mode. set to always uses channel input from sample A.
AD1CON3 = 0; // set everything to zero to start with.
AD1CON3bits.ADRC = 0; // ADC conversion clock derived from system clock.
AD1CON3bits.SAMC = 0; // auto sample time bits, TAD, set to 0.
AD1CON3bits.ADCS = 0; // ADC conversion clock set to 0. 1 * TCY = TAD.
AD1CON4 = 0; // set everything to zero to start with.
AD1CON4bits.DMABL = 0; // allocates 1 word of buffer to each analogue input.
AD1CHS123 = 0; // everything set to zero as not using channels 1, 2, or 3.
AD1CHS0 = 0; // set everything to zero to start with.
AD1CHS0bits.CH0NB = 0; // channel 0 negative input, set by CH0NA. sample B.
AD1CHS0bits.CH0SB = 0; // channel 0 positive input, set by CH0SA. sample B.
AD1CHS0bits.CH0NA = 0; // channel 0 negative input, for sample A. set to VREFL.
AD1CHS0bits.CH0SA = 0; // channel 0 positive input is AN0.
AD1CSSL = 0; // input scan register set to zero as not using it.
AD1PCFGL = 0; // port configuration, set to analogue mode, ADC samples voltage.
AD1CON1bits.ADON = 1; // turn on ADC
AD1CON1bits.SAMP = 1; // Start sampling
DELAY(1); // Wait for sampling time (1ms)
AD1CON1bits.SAMP = 0; // Start the conversion
while (!AD1CON1bits.DONE); // Wait for the conversion to complete
ADCValue = ADC1BUF0; // Read the conversion result
while (1);
}
我使用 PIC 使用的相同轨道为传感器供电，并且我将传感器的输出连接到 AN0（引脚 2），正如我在代码中设置的那样。PIC 由标准 Vss 和 Vdd（引脚 8 和 13）、模拟电源引脚 AVdd 和 AVss（引脚 28 和 27）以及 Vcap 和 Vss（引脚 20 和 19）之间的 33uF 电容器供电。我还需要在硬件方面做些什么吗？我对 AD1CHS0bits.CH0NA 寄存器有点困惑，因为我不知道是否必须将地连接到 VREFL 或在这种情况下该怎么做。
任何关于我应该做些什么来纠正这个问题的帮助将不胜感激！此外，任何有关如何在正确接收到值后转换值的帮助都将非常有帮助。