v3_firmware/lib/SG112A/SG112A.cpp

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/*
SG112A.cpp - SG112A Sensor Library
Copyright (c) 2020-2021, Stefan Brand
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
1. Redistributions of source code must retain the above copyright notice, this
list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation
and/or other materials provided with the distribution.
3. Neither the name of the copyright holder nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
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#include <Arduino.h>
#include "SG112A.h"
// Constructor - Inititalize Hardware UART
SG112A::SG112A(void) {
Serial.begin(9600);
Serial.setTimeout(READ_TIMEOUT);
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}
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uint8_t SG112A::getSensorData(char *payload, uint8_t startbyte) {
write(CMD_GET_PPM);
delay(50);
uint8_t readBytes = read();
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payload[startbyte] = 0x00;
payload[startbyte+1] = 0x00;
if (readBytes > 0) {
switch(buffer[2]) {
case 0x15:
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uint16ToPayload((buffer[3]*256) + buffer[4], payload, startbyte);
break;
}
}
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return startbyte+2;
}
// Write a Command to the Sensor
void SG112A::write(byte cmd) {
uint8_t _cmd[6] = {0xAA, 0x55, cmd, 0x00, 0x00, 0x00};
uint16_t crc = crc16(_cmd, 4);
_cmd[4] = (uint8_t)(crc & 0xFF);
_cmd[5] = (uint8_t)(crc >> 8);
while (Serial.available() > 0) Serial.read();
Serial.write(_cmd, 6);
Serial.flush();
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}
// Read a Sensor Response
uint8_t SG112A::read() {
// Number of returned Bytes
uint8_t ret = 0;
// Clear Internal Buffer
zeroBuffer();
// Read Available Bytes
if (Serial.available() > 0) {
ret = Serial.readBytes(buffer, SER_BUF_LEN);
}
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// Check Sync Bytes
if (buffer[0] != 0xBB || buffer[1] != 0x66)
return 0;
// Check CRC of the Returned Messages
uint16_t crc = crc16(buffer, ret-2);
if (buffer[ret-1] != (uint8_t)(crc >> 8) || buffer[ret-2] != (uint8_t)(crc & 0xFF))
return 0;
return ret;
}
// Fill the Internal Buffer with Zeroes
void SG112A::zeroBuffer() {
for (int i=0; i < SER_BUF_LEN; i++)
buffer[i] = 0x00;
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}
// Calculate 16Bit CRC of Messages and Commands
uint16_t SG112A::crc16(uint8_t *cmd, int len){
uint16_t ret = 0xffff;
uint16_t polynomial = 0xa001;
int shift = 0x0;
int i = 0;
for (i = len - 1; i >= 0 ; i-- ){
uint16_t code = ( uint16_t )( cmd [ len -1 - i ] & 0xff );
ret = ret^code;
shift = 0x0;
while ( shift <= 7 ){
if ( ret & 0x1 ) {
ret = ret >> 1;
ret = ret^polynomial ;
} else {
ret = ret >> 1;
}
shift++;
}
}
return ret;
}