mhz19_internals.h

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/*
 * Copyright (C) 2018 Koen Zandberg <koen@bergzand.net>
 *
 * This file is subject to the terms and conditions of the GNU Lesser
 * General Public License v2.1. See the file LICENSE in the top level
 * directory for more details.
 */
 
#pragma once

 
#ifdef __cplusplus
extern "C" {
#endif

#define MHZ19_UART_BAUDRATE 9600

#define MHZ19_BUF_SIZE      8

#define MHZ19_TIMEOUT_READ  20
 
/***
 * @name MH-Z19 Command timeout in milliseconds
 *
 * While undocumented, it seems that some commands take some time. Without
 * an additional delay, the first sensor read will fail with a timeout value,
 * or return an arbitrary value.
 */
#define MHZ19_TIMEOUT_CMD   (MHZ19_TIMEOUT_READ * 5)

#define MHZ19_READ_START                0xff    
#define MHZ19_READ_SENSOR_NUM           0x01    

#define MHZ19_CMD_AUTO_CALIBRATION      0x79    
#define MHZ19_CMD_GAS_CONCENTRATION     0x86    
#define MHZ19_CMD_CALIBRATE_ZERO        0x87    
#define MHZ19_CMD_CALIBRATE_SPAN        0x88    

#define MHZ19_RX_POS_PPM_HIGH           1   
#define MHZ19_RX_POS_PPM_LOW            2   
#define MHZ19_RX_POS_CHECKSUM           7   
 
#ifdef __cplusplus
}
#endif