我static volatile在我的类中定义了两个变量ADC。该类写为：（裁剪以节省空间）
#pragma once
#include "../PeriodicProcess/PeriodicProcess.h"
#include <stdint.h>
#include <stdlib.h>
class ADC
{
private:
static inline unsigned char SPI_transfer(unsigned char data);
void read(uint32_t tnow);
static const unsigned char adc_cmd[9];
static volatile uint32_t _sum[8];
static volatile uint16_t _count[8];
public:
ADC();
void raw();
void init(PeriodicProcess * scheduler);
double ch(uint8_t c);
bool available(const uint8_t *channelNumbers);
uint32_t ch6(const uint8_t *channelNumbers, double *result);
};
但是编译项目会在第 10、29、39 和 44 行的 cpp 文件中引发错误：
ADC.cpp 到目前为止：
#include "ADC.h"
extern "C" {
// AVR LibC Includes
#include <inttypes.h>
#include <stdint.h>
#include <avr/interrupt.h>
}
#include "Arduino.h"
const unsigned char ADC::adc_cmd[9] = { 0x87, 0xC7, 0x97, 0xD7, 0xA7, 0xE7, 0xB7, 0xF7, 0x00 };
#define bit_set(p,m) ((p) |= ( 1<<m))
#define bit_clear(p,m) ((p) &= ~(1<<m))
// We use Serial Port 2 in SPI Mode
#define ADC_DATAOUT 51 // MOSI
#define ADC_DATAIN 50 // MISO
#define ADC_SPICLOCK 52 // SCK
#define ADC_CHIP_SELECT 33 // PC4 9 // PH6 Puerto:0x08 Bit mask : 0x40
// DO NOT CHANGE FROM 8!!
#define ADC_ACCEL_FILTER_SIZE 8
#define TCNT2_781_HZ (256-80)
#define TCNT2_1008_HZ (256-62)
#define TCNT2_1302_HZ (256-48)
unsigned char ADC::SPI_transfer(unsigned char data)
{
// Put data into buffer, sends the data
UDR2 = data;
// Wait for data to be received
while ( !(UCSR2A & (1 << RXC2)) );
// Get and return received data from buffer
return UDR2;
}
ADC::ADC()
{
//Do nothing
}
void ADC::read(uint32_t tnow)
{
uint8_t ch;
bit_clear(PORTC, 4); // Enable Chip Select (PIN PC4)
ADC_SPI_transfer(adc_cmd[0]); // Command to read the first channel
for (ch = 0; ch < 8; ch++) {
uint16_t v;
v = ADC_SPI_transfer(0) << 8; // Read first byte
v |= ADC_SPI_transfer(adc_cmd[ch + 1]); // Read second byte and send next command
if (v & 0x8007) {
// this is a 12-bit ADC, shifted by 3 bits.
// if we get other bits set then the value is
// bogus and should be ignored
continue;
}
if (++_count[ch] == 0) {
// overflow ... shouldn't happen too often
// unless we're just not using the
// channel. Notice that we overflow the count
// to 1 here, not zero, as otherwise the
// reader below could get a division by zero
_sum[ch] = 0;
_count[ch] = 1;
}
_sum[ch] += (v >> 3);
}
bit_set(PORTC, 4); // Disable Chip Select (PIN PC4)
}
void ADC::init(AP_PeriodicProcess * scheduler)
{
pinMode(ADC_CHIP_SELECT, OUTPUT);
digitalWrite(ADC_CHIP_SELECT, HIGH); // Disable device (Chip select is active low)
// Setup Serial Port2 in SPI mode
UBRR2 = 0;
DDRH |= (1 << PH2); // SPI clock XCK2 (PH2) as output. This enable SPI Master mode
// Set MSPI mode of operation and SPI data mode 0.
UCSR2C = (1 << UMSEL21) | (1 << UMSEL20); // |(0 << UCPHA2) | (0 << UCPOL2);
// Enable receiver and transmitter.
UCSR2B = (1 << RXEN2) | (1 << TXEN2);
// Set Baud rate
UBRR2 = 2; // SPI clock running at 2.6MHz
// get an initial value for each channel. This ensures
// _count[] is never zero
for (uint8_t i=0; i<8; i++) {
uint16_t adc_tmp;
adc_tmp = ADC_SPI_transfer(0) << 8;
adc_tmp |= ADC_SPI_transfer(adc_cmd[i + 1]);
_count[i] = 1;
_sum[i] = adc_tmp;
}
last_ch6_micros = micros();
scheduler->register_process( AP_ADC_ADS7844::read );
}
// Read one channel value
double ADC::ch(uint8_t c)
{
uint16_t count;
uint32_t sum;
// Ensure we have at least one value
while (_count[c] == 0); // Waiting while
// grab the value with interrupts disabled, and clear the count
cli();
count = _count[c];
sum = _sum[c];
_count[c] = 0;
_sum[c] = 0;
sei();
return ((double)sum)/count;
}
// See if Ch6() can return new data
bool ADC::available(const uint8_t *channelNumbers)
{
uint8_t i;
for (i=0; i<6; i++)
{
if (_count[channelNumbers[i]] == 0)
{
return false;
}
}
return true;
}
// Read 6 channel values
// this assumes that the counts for all of the 6 channels are
// equal. This will only be true if we always consistently access a
// sensor by either Ch6() or Ch() and never mix them. If you mix them
// then you will get very strange results
uint32_t ADC::ch6(const uint8_t *channelNumbers, double *result)
{
uint16_t count[6];
uint32_t sum[6];
uint8_t i;
// Ensure we have at least one value
for (i=0; i<6; i++)
{
while (_count[channelNumbers[i]] == 0); // Waiting while
}
// Grab the values with interrupts disabled, and clear the counts
cli();
for (i=0; i<6; i++)
{
count[i] = _count[channelNumbers[i]];
sum[i] = _sum[channelNumbers[i]];
_count[channelNumbers[i]] = 0;
_sum[channelNumbers[i]] = 0;
}
sei();
// Calculate averages. We keep this out of the cli region
// to prevent us stalling the ISR while doing the
// division. That costs us 36 bytes of stack, but I think its
// worth it.
for (i = 0; i < 6; i++)
{
result[i] = (sum[i] + count[i]) / (double)count[i];
}
// Return number of microseconds since last call
uint32_t us = micros();
uint32_t ret = us - last_ch6_micros;
last_ch6_micros = us;
return ret;
}
错误报告提供：
ADC.cpp:10: error: expected unqualified-id before 'volatile'
ADC.cpp:10: error: expected `)' before 'volatile'
ADC.cpp:10: error: expected `)' before 'volatile'
ADC.cpp:29: error: expected unqualified-id before 'volatile'
ADC.cpp:29: error: expected `)' before 'volatile'
ADC.cpp:29: error: expected `)' before 'volatile'
ADC.cpp:39: error: expected unqualified-id before 'volatile'
ADC.cpp:39: error: expected `)' before 'volatile'
ADC.cpp:39: error: expected `)' before 'volatile'
ADC.cpp:44: error: expected unqualified-id before 'volatile'
ADC.cpp:44: error: expected `)' before 'volatile'
ADC.cpp:44: error: expected `)' before 'volatile'
这里有什么问题？为什么它指向我的常量静态定义？为什么它讨厌我的 3 个类方法？为什么在该行上不存在 volatile 的情况下期望 volatile 为 ')'？为什么它期待一个不合格的ID（不应该反过来）？