Reference

Library

• Library files: DFRobot_GasSensor Library
• Installation instructions: Download the library and install it via Arduino IDE's "Sketch > Include Library > Add .ZIP Library" menu.
• Usage examples: Refer to the "examples" folder in the library, including passive/initiative data acquisition and threshold alarm.

Serial port protocol usage tutorial

Through the UART serial communication protocol, you can connect DFR0784 Gravity: Electrochemical Smart Gas Sensor Terminal to any controller with UART for data reading and sensor configuration.
Note: At this time, the SEL end of the DIP switch on the sensor must be placed in the "1" position

Serial Port Parameter Setting

Communication Protocol Description

① 0x78——Modify Terminal Communication Mode

The terminal has two communication modes, active uploading and question and answer. The factory default is active uploading mode, and data is sent every 1s.

Send

EXP.FF 01 78 03 00 00 00 00 84 (switch to initiative mode)
EXP.FF 01 78 04 00 00 00 00 83 (switch to passive mode)

Return

EXP.FF 78 01 00 00 00 00 00 87

② Initiative Mode，Data Format

In the active upload mode, the terminal will return data every 1s. The data format is as follows.

Return

Note:

• Gas concentration value = (high gas concentration x 256 + low gas concentration) x resolution
• The decimal place is 0, the resolution is 1; the decimal place is 1, the resolution is 0.1; the decimal place is 2, the resolution is 0.01
• For the calculation method of temperature value, please refer to the sample code below: "Calculation of temperature value"

Gas Type Table

③ 0x86——Passive Mode, Read Gas Concentration Data

In the question and answer mode, you need to send commands to read various parameters of the terminal. The method of reading the gas concentration is as follows.

Send

EXP.FF 01 86 00 00 00 00 00 79

Return

EXP.FF 86 00 00 00 00 00 00 7A

Note:

• Gas concentration value = (high gas concentration x 256 + low gas concentration) x resolution
• The decimal place is 0, the resolution is 1; the decimal place is 1, the resolution is 0.1; the decimal place is 2, the resolution is 0.01

④ 0x87——Passive Mode, Read Temperature Data

In the question and answer mode, you need to read various parameters of the terminal by sending commands. The terminal integrates the thermistor, which can obtain the real-time temperature of the terminal. The way to read the terminal temperature is as follows.

Send

EXP.FF 01 87 00 00 00 00 00 78

Return

EXP.FF 87 00 00 00 00 00 00 79

Note:
For the calculation method of temperature value, please refer to the sample code below: "Calculation of temperature value"

⑤ 0x88——Passive Mode, Read Temperature and Gas Concentration Data

In the question and answer mode, you need to read various parameters of the terminal by sending commands, and the way to read the temperature and gas concentration data of the terminal is as follows.

Send

EXP.FF 01 88 00 00 00 00 00 77

Return

EXP. FF 88 00 00 00 00 00 00 78

Note:

• Gas concentration value = (high gas concentration x 256 + low gas concentration) x resolution
• The decimal place is 0, the resolution is 1; the decimal place is 1, the resolution is 0.1; the decimal place is 2, the resolution is 0.01
• For the calculation method of temperature value, please refer to the sample code below: "Calculation of temperature value"

⑥ 0x89——Configure Threshold Alarm Function

The terminal has a threshold alarm function, the alarm threshold and judgment logic can be configured. The configuration method is as follows,After the configuration is successful, the entire system needs to be powered on again to take effect.

Note: When no external controller is connected and only the sensor is used to achieve this function, the sensor must be set to active upload mode after the parameters related to the threshold alarm function are configured.

Send

EXP. FF 01 89 00 00 05 00 00 71 (turn off the alarm function)
EXP. FF 01 89 01 00 05 00 00 70 (open the alarm function)

Please refer to ⑤ for how to calculate the concentration.

Return

To configure the threshold alarm by code using a controller such as Raspberry Pi, you can use this python code: GAS_ALA.zip

Checksum Calculation

unsigned char data[] = {0xFF,0x01,0x87,0x00,0x00,0x00}; 

unsigned char FucCheckSum(unsigned char *i,unsigned char ln)
{ 
    unsigned char j,tempq=0; 
    i+=1; 
    for(j=0;j<6;j++) 
    { 
        tempq+=*i; 
        i++; 
    } 
    tempq=(~tempq)+1; 
    return(tempq); 
}

void setup() {
  Serial.begin(115200);
  Serial.println(FucCheckSum(data,6),HEX); 
}

void loop() {

}

Calculation of Temperature Value

byte Temp_H = 0x01;//Temperature data high bit
byte Temp_L = 0xD9;//Temperature data low bit

void setup() {
  Serial.begin(115200);
  uint16_t temp_ADC = (Temp_H << 8) + Temp_L;
  float Vpd3 = 3 * (float)temp_ADC / 1024;
  float Rth = Vpd3 * 10000 / (3 - Vpd3);
  float Temp = 1 / (1 / (273.15 + 25) + 1 / 3380.13 * log(Rth / 10000)) - 273.15;
  Serial.println(Temp);
}

void loop() {

}

API Description

DFR0784 Gravity: Electrochemical Smart Gas Sensor Terminal There are two data reading modes: active upload and passive response. The factory default is active upload mode, and users can adjust them in the code according to their needs.

Mode Selection Function "changeAcquireMode()"

Modify the parameters in brackets of the "changeAcquireMode()" function to adjust the data sending mode.

"INITIATIVE" is the active upload mode. In the active upload mode, the sensor will automatically upload parameters every 1 second;
"PASSIVITY" is the passive response mode. In the passive response mode, the sensor will feedback the parameters only every time the data reading function is called.

gas.changeAcquireMode(gas.INITIATIVE)
/*
      gas.INITIATIVE            // Active upload mode
      gas.PASSIVITY             // Passive response mode
*/

Set the Probe Type Function "setGasType()"

Set the probe type by the "setGasType()" function.

gas.setGasType(/*Gas type*/gas.O2);

Read the Probe Type Function "queryGasType()"

Through the "queryGasType()" function, You can get the type of current gas probe.

gas.queryGasType();

For probe compatible types and corresponding parameters, please refer to the table below.

Gas Concentration Reading Function "readGasConcentrationPPM()"

The feedback gas concentration value of the gas sensor can be read through the "readGasConcentrationPPM()" function.

gas.readGasConcentrationPPM();

Temperature Reading Function "readTempC()"

The onboard temperature sensor data can be read through the "readTempC()" function.

gas.readTempC();

Voltage Reading Function "getSensorVoltage()"

The original voltage output V0 of the gas probe can be read through the "getSensorVoltage()" function.

gas.getSensorVoltage();

Configure Temperature Compensation Function "setTempCompensation()"

You can enable/disable the temperature compensation function through the "setTempCompensation()" function.

gas.setTempCompensation();
/*
  \tgas.ON  \tTurn on
  \tgas.OFF\t\tTurn off
*/

Threshold Alarm Function "setThresholdAlarm()"

You can configure the threshold alarm information through the "setThresholdAlarm()" function

gas.setThresholdAlarm(gas.ON, 200, gas.LOW_THRESHOLD_ALA ,gas.queryGasType());
/*
\tgas.ON  \tTurn on
  \tgas.OFF\t\tTurn off
  \t200\t\t\tSet threshold
  \tgas.LOW_THRESHOLD_ALA Jump to low level when alarming
  \tgas.HIGH_THRESHOLD_ALA Jump to high level when alarming
  \tgas.queryGasType() Set alarm gas type
*/

I2C Address Group Configuration Function "changeI2cAddrGroup()"

You can configure the I2C address group code and switch between different address groups through the "changeI2cAddrGroup()" function.

In order to prevent address conflicts when using multiple sensors, we have prepared 8 groups with a total of 23 addresses. If necessary, You can use "change_sensor_iic_addr.ino" in the library file "example",to switch by modifying the group serial number configuration of "changeI2cAddrGroup()". After the serial port information displays "IIC addr change success!", power on again.

gas.changeI2cAddrGroup(i);
 /* 
 \ti\t\t\tGroup number

  //Group serial number and DIP switch configuration table
  A0 A1Dial level    00    01    10    11
  Group number          Group address
    1            0x60  0x61  0x62  0x63
    2            0x64  0x65  0x66  0x67
    3            0x68  0x69  0x6A  0x6B
    4            0x6C  0x6D  0x6E  0x6F
    5            0x70  0x71  0x72  0x73
    6（Default address group） 0x74  0x75  0x76  0x77
    7            0x78  0x79  0x7A  0x7B
    8            0x7C  0x7D  0x7E  
 */

Other Supplementary Information

• DFRobot-Electrochemical Module .pdf
• Dimension.pdf
• 3D model