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SFM3300.cpp
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SFM3300.cpp
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#include "SFM3300.h"
#include <Wire.h>
SFM3300::SFM3300(uint8_t i2c_addr)
{
SFM3300_Address = i2c_addr;
}
void SFM3300::begin()
{
Wire.begin();
// Soft reset Command 0x2000
Wire.beginTransmission(SFM3300_Address);
Wire.write(0x20);
Wire.write(0x00);
Wire.endTransmission();
delay(100);
// Start Flow Measurement Command 0x1000
Wire.beginTransmission(SFM3300_Address);
Wire.write(0x10);
Wire.write(0x00);
Wire.endTransmission();
delay(100);
// Read the first invalid data from sensor after initialization
Wire.requestFrom(SFM3300_Address, 3);
uint16_t a = Wire.read();
uint8_t b = Wire.read();
uint8_t crc = Wire.read();
Wire.endTransmission();
delay(10);
}
void SFM3300::reset() {
delay(10);
asm volatile ("jmp 0");
}
typedef enum {
CHECKSUM_ERROR = 0X04
} etError;
#define POLYNOMIAL 0x131 //P(x)=x^8+x^5+x^4+1 = 100110001
//=============================================================================
uint8_t SMF3300_CheckCrc (uint8_t data[], uint8_t nbrOfBytes, uint8_t checksum)
//=============================================================================
// calculates checksum for n bytes of data
// and compares it with expected checksum
// Input: data[] checksum is built based on this data
// nbrOfBytes checksum is built for n bytes of data
// checksum expected checksum
// Return: error: CHECKSUM_ERROR = checksum does not match
// 0 = checksum matches
//=============================================================================
{
uint8_t crc = 0;
uint8_t byteCtr;
// Calculates 8-Bit checksum with given polynomial
for (byteCtr = 0; byteCtr < nbrOfBytes; ++byteCtr) {
crc ^= (data[byteCtr]);
for (uint8_t bit = 8; bit > 0; --bit) {
if (crc & 0x80) crc = (crc << 1) ^ POLYNOMIAL;
else crc = (crc << 1);
}
}
if (crc != checksum) return CHECKSUM_ERROR;
else return 0;
}
int count = 0;
int SFM3300::getValue()
{
if (3 == Wire.requestFrom(SFM3300_Address, 3)) {
count = 0;
uint8_t readByte[2];
uint16_t a = readByte[0] = Wire.read();
uint8_t b = readByte[1] = Wire.read();
uint8_t crc = Wire.read();
if (SMF3300_CheckCrc(readByte, 2, crc)) {
//Serial.println("Error: wrong CRC");
}
a = (a << 8) | b;
int Flow = a;
return Flow;
}
else {
// Failed sensor reading
count ++;
if (count >= 2) {
// Software reset the microcontroller unit
delay(10);
asm volatile ("jmp 0");
}
}
}
void SFM3300::hardReset(uint8_t sensorPowerPin)
{
pinMode(sensorPowerPin, OUTPUT);
for (;;) {
// Switch the NPN BJT transistor to hard reset the sensor
digitalWrite(sensorPowerPin, LOW);
delay(500);
digitalWrite(sensorPowerPin, HIGH);
delay(100);
break;
}
}