我一直试图弄清楚为什么我无法通过将无符号整数与浮点值相乘来获得合理的值。
执行 65535*0.1 之类的操作按预期工作，但是将浮点数与内存中的 uint 相乘会产生疯狂的值。我有一个读取 ADC 并返回 uin16_t 的函数。使用此值，我将其打印到 4 位 LED 显示屏上，效果很好。
将相同的值乘以 1.0 会返回完全不同的结果（它对我的显示器来说太大了，所以我真的不知道它是什么）。
我的代码在下面，但争用区域在 main() 的底部。任何帮助都会很棒。谢谢
主.c：
#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>
#include <stdint.h>
#define BAUD 9600
#include <util/setbaud.h>
#define DISP_BRIGHT_CMD 'z'
#define DISP_RESET 'v'
#define ADC_AVG 3
volatile uint8_t hi,lo;
volatile uint16_t result;
ISR(ADC_vect)
{
lo = ADCL;
hi = ADCH;
MCUCR &= ~_BV(SE); //Clear enable sleep
}
void initSerial(void)
{
// set baud rate
UBRR0H = UBRRH_VALUE;
UBRR0L = UBRRL_VALUE;
// set frame format
UCSR0C |= (0x3 << UCSZ00); // 8n1
// set enable tx/rx
UCSR0B = _BV(RXEN0) | _BV(TXEN0);
}
void initADC(void)
{
// AVCC and ADC0
ADMUX = _BV(REFS0);
// Enable, div128, + 1st setup
ADCSRA |= _BV(ADEN)|_BV(ADSC)|_BV(ADPS2)|_BV(ADPS1)|_BV(ADPS0)|_BV(ADIE);
}
uint16_t readADC(void)
{
uint16_t average=0;
// Start Conversion
ADCSRA |= _BV(ADSC);
for (char i=0;i<ADC_AVG;i++) {
MCUCR |= _BV(SE);
ADCSRA |= _BV(ADSC);
__asm volatile("sleep");
MCUCR &= ~_BV(SE);
result = (hi<<8);
result |= lo;
average += result;
}
average /= ADC_AVG;
return average;
}
void sendByte(char val)
{
while (! (UCSR0A & (1<<UDRE0)) ); //wait until tx is complete
UDR0 = val;
}
/*
* Convert voltage to temperature based on a negative coefficient for MAX6613
*/
uint16_t analogToTemp(uint16_t val)
{
uint16_t temp;
//v = 5 * (val/1023.0);
//temp = (1.8455 - (5.0*(val/1023.0)))/0.01123;
temp = (1.8455 - (5.0*(val/1023.0)))*89;
//temp = val * M_PI;
//v = 5 * ( val/1024);
//temp = (2 - v) * 89;
return temp;
}
void initDisplay()
{
sendByte(DISP_RESET);
sendByte(DISP_BRIGHT_CMD);
sendByte(0);
}
void serialSegments(uint16_t val)
{
// 4 digit display
sendByte(val / 1000);
sendByte((val / 100) % 10);
sendByte((val / 10) % 10);
sendByte(val % 10);
}
int main(void)
{
uint16_t calc=0,sense=0;
DDRB |= _BV(DDB5);
PORTB |= _BV(PORTB5);
initSerial();
initADC();
initDisplay();
sei();
MCUCR |= (1 << SM0); // Setting sleep mode to "ADC Noise Reduction"
MCUCR |= (1 << SE); // Sleep enable
for(;;) {
//PORTB ^= _BV(PORTB5);
if (calc>=9999){ // I can't see the real value. Max val on display is 9999
//if (sense>=330){
PORTB |= _BV(PORTB5);
} else {
PORTB &= ~_BV(PORTB5);
}
sense = readADC();
//calc = sense*1.0; // refuses to calculate properly
calc = analogToTemp(sense); // a bunch of zeroes
//calc = 65535*0.1; // a-ok
serialSegments(calc);
_delay_ms(500);
serialSegments(sense);
_delay_ms(500);
}
return 0;
}
生成文件：
# AVR-GCC Makefile
PROJECT=Temp_Display
SOURCES=main.c
CC=avr-gcc
OBJCOPY=avr-objcopy
MMCU=atmega328p
OSC_HZ=16000000UL
OPTIMISATION=2
PORT=/dev/ttyUSB0
CFLAGS=-mmcu=${MMCU} -std=gnu99 -Wall -O${OPTIMISATION} -DF_CPU=${OSC_HZ} -lm -lc
${PROJECT}.hex: ${PROJECT}.out
${OBJCOPY} -j .text -O ihex ${PROJECT}.out ${PROJECT}.hex
avr-size ${PROJECT}.out
$(PROJECT).out: $(SOURCES)
${CC} ${CFLAGS} -I./ -o ${PROJECT}.out ${SOURCES}
program: ${PROJECT}.hex
stty -F ${PORT} hupcl
avrdude -V -F -c arduino -p m168 -b 57600 -P ${PORT} -U flash:w:${PROJECT}.hex
clean:
rm -f ${PROJECT}.out
rm -f ${PROJECT}.hex
编辑： 好的，我已经稍微简化了代码
#include <avr/io.h>
#include <util/delay.h>
#include <stdint.h>
#define BAUD 9600
#include <util/setbaud.h>
#define DISP_BRIGHT_CMD 'z'
#define DISP_RESET 'v'
void initSerial(void)
{
// set baud rate
UBRR0H = UBRRH_VALUE;
UBRR0L = UBRRL_VALUE;
// set frame format
UCSR0C |= (0x3 << UCSZ00); // 8n1
// set enable tx/rx
UCSR0B = _BV(TXEN0);
}
void sendByte(char val)
{
while (! (UCSR0A & (1<<UDRE0)) ); //wait until tx is complete
UDR0 = val;
}
void initDisplay()
{
sendByte(DISP_RESET);
sendByte(DISP_BRIGHT_CMD);
sendByte(0);
}
void serialSegments(uint16_t val) {
// 4 digit display
sendByte(val / 1000);
sendByte((val / 100) % 10);
sendByte((val / 10) % 10);
sendByte(val % 10);
}
int main(void)
{
uint16_t i=0,val;
DDRB |= _BV(DDB5);
initSerial();
initDisplay();
for(;;) {
val = (uint16_t)(i++ * 1.5);
serialSegments(i);
_delay_ms(500);
serialSegments(val);
_delay_ms(500);
if (val > 9999){
PORTB |= _BV(PORTB5);
} else {
PORTB &= ~_BV(PORTB5);
}
}
return 0;
}