103 lines
3.3 KiB
C++
103 lines
3.3 KiB
C++
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/*
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MHZ19C.cpp - MHZ19C Sensor Library
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Copyright (c) 2020-2021, Stefan Brand
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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1. Redistributions of source code must retain the above copyright notice, this
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list of conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright notice,
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this list of conditions and the following disclaimer in the documentation
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and/or other materials provided with the distribution.
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3. Neither the name of the copyright holder nor the names of its
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contributors may be used to endorse or promote products derived from
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this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <Arduino.h>
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#include "MHZ19C.h"
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// Constructor - Inititalize Hardware UART
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MHZ19C::MHZ19C(void) {
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Serial.begin(9600);
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Serial.setTimeout(MHZ19C_READ_TIMEOUT);
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}
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void MHZ19C::getSensorData(lora_data &loradata) {
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write(MHZ19C_CMD_GET_PPM, 0x00);
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delay(50);
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uint8_t readBytes = read();
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loradata.ppm = 0;
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if (readBytes > 0) {
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switch(buffer[1]) {
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case 0x86:
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loradata.ppm = (buffer[2]*256) + buffer[3];
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break;
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}
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}
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}
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// Turn Self Calibration Routine On or Off
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void MHZ19C::setSelfCalibration(bool state) {
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if (state) {
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write(0x79, 0xA0);
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} else {
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write(0x79, 0x00);
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}
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}
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// Write a Command to the Sensor
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void MHZ19C::write(uint8_t cmd, uint8_t arg) {
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uint8_t _cmd[9] = {0xFF, 0x01, cmd, arg, 0x00, 0x00, 0x00, 0x00, 0x00};
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uint8_t crc = crc8(_cmd);
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_cmd[8] = crc;
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while (Serial.available() > 0) Serial.read();
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Serial.write(_cmd, 9);
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Serial.flush();
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}
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// Read a Sensor Response
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uint8_t MHZ19C::read() {
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uint8_t ret = 0;
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zeroBuffer();
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// Read Available Bytes
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if (Serial.available() > 0) {
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ret = Serial.readBytes(buffer, MHZ19C_SER_BUF_LEN);
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}
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// Check Sync Bit and CRC
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if (buffer[0] != 0xFF || buffer [8] != crc8(buffer))
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return 0;
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// Return Read Bytes
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return ret;
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}
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// Fill the Internal Buffer with Zeroes
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void MHZ19C::zeroBuffer() {
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for (int i=0; i < MHZ19C_SER_BUF_LEN; i++)
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buffer[i] = 0x00;
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}
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// Calculate 8Bit CRC of Messages and Commands
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uint8_t MHZ19C::crc8(uint8_t *paket){
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uint8_t i, checksum = 0x00;
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for( i = 1; i < 8; i++)
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checksum += paket[i];
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checksum = 0xff - checksum;
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checksum += 1;
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return checksum;
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}
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