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    AHT20 Humidity + Temperature Sensor

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    • J Offline
      JohnGalt
      last edited by

      Does anyone know of a module that will display the output from AHT20 temperature + humidity sensors? I got these after having used the older DHTxx sensors in the past. These new sensors use I2C, and I have confirmed the sensor is wired up correctly and sending data by using an example script.

      Now I’d like to get the output on the Magic Mirror. While I do see some modules that read from I2C compatible sensors, I haven’t seen one that reads these.

      Currently I an working with these two modules, both to no avail:
      MMMiTemperature: https://github.com/Tom-Hirschberger/MMM-Temperature
      and
      MMM-BME280: https://github.com/awitwicki/MMM-BME280

      R 1 Reply Last reply Reply Quote 0
      • R Offline
        rkorell @JohnGalt
        last edited by

        @JohnGalt Good morning,
        do you have connected the sensors locally to the same PI where the mirror is running?
        What script are you using and what output this sends?
        If you are able to modify these scripts to deliver a JSON output you may can use MMM-JsonValue for displaying the results…

        Regards,
        Ralf

        J 2 Replies Last reply Reply Quote 0
        • J Offline
          JohnGalt @rkorell
          last edited by

          @rkorell – Thanks for responding, answers follow:

          1. Yes, the first use case is a sensor connected directly to the Raspberry Pi 4 where the Magic Mirror is running. It will be great if I can expand this in the future to display on my office Magic Mirror the outputs from sensors on three (3) other Pis (they run Magic Mirror, NEMS network monitor and Pi-Aware flight tracking, respectively).

          2. I am just running the two Magic Mirror modules listed above. I don’t know what scripts they run. At this point I have just looked and don’t see any obvious way to adapt them. I did try changing the address of the device from their default to 0x38, which is what I think is the address for this sensor attached to my Pi - but I still don’t get output. I should have some time this afternoon to SSH into that machine, and I can locate the scripts and log the error messages.

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          • J Offline
            JohnGalt @rkorell
            last edited by

            @rkorell Ralf: OK, I have a chance to work on this today - Thanks for your help.

            To ease troubleshooting, I have temporarily disabled MMM-Temperature and am only running MMM-BME280. Below are the following:

            1. Config for this module
            2. Error as captured using pm2 logs
            3. Code listing of bme280.js, which is called by the module

            Config:

            {module: 'MMM-BME280', // https://github.com/awitwicki/MMM-BME280
              disabled: false,
              position: 'top_right',
              config: {
                titleText: "Office - MMM-BME280",
                updateInterval: 100, //seconds 
                deviceAddress: "0x38", //0x76 = default
                temperatureScaleType: 1, // 0=Celsius
                pressureScaleType: 1, // 0 = hPa
            	} },
            

            Errors [from pm2 logs]:
            0|MagicMirror | [2025-04-15 12:57:48.599] [ERROR] exec error: Error: Command failed: python3 ./modules/MMM-BME280/bme280.py 0x38
            0|MagicMirror | Traceback (most recent call last):
            0|MagicMirror | File “/home/pi/MagicMirror/./modules/MMM-BME280/bme280.py”, line 176, in
            0|MagicMirror | main()
            0|MagicMirror | File “/home/pi/MagicMirror/./modules/MMM-BME280/bme280.py”, line 171, in main
            0|MagicMirror | temperature,pressure,humidity = readBME280All()
            0|MagicMirror | File “/home/pi/MagicMirror/./modules/MMM-BME280/bme280.py”, line 82, in readBME280All
            0|MagicMirror | bus.write_byte_data(addr, REG_CONTROL_HUM, OVERSAMPLE_HUM)
            0|MagicMirror | OSError: [Errno 121] Remote I/O error
            0|MagicMirror |

            Code for bme280.py:

            Module.register("MMM-BME280", {
                // Default module config.
                defaults: {
                    updateInterval: 100, // Seconds
                    titleText: "Home weather",
                    deviceAddress: "0x76",
                    temperatureScaleType: 0, // Celsuis
                    pressureScaleType: 0 // hPa
                },
            
                // Define start sequence.
                start: function () {
                    Log.info("Starting module: " + this.name);
            
                    this.temperature = 'Loading...';
                    this.humidity = 'Loading...';
                    this.pressure = 'Loading...';
            
                    this.update();
                    setInterval(
                        this.update.bind(this),
                        this.config.updateInterval * 1000);
                },
            
                update: function () {
                    this.sendSocketNotification('REQUEST', this.config);
                },
            
                getStyles: function () {
                    return ['MMM-BME280.css'];
                },
            
                // Override dom generator.
                getDom: function () {
                    var wrapper = document.createElement("div");
            
                    var header = document.createElement("div");
                    var label = document.createTextNode(this.config.titleText);
                    header.className = 'bme-header';
                    header.appendChild(label)
                    wrapper.appendChild(header);
            
                    var table = document.createElement("table");
                    var tbdy = document.createElement('tbody');
                    for (var i = 0; i < 3; i++) {
                        var val = "";
                        var sufix = "";
                        var icon_img = "";
            
                        switch (i) {
                            case 0:
                                switch (this.config.temperatureScaleType) {
                                    case 0: // Celsius
                                        val = this.temperature;
                                        sufix = "°C";
                                        break;
                                    case 1: // Fahrenheit
                                        val = Math.round(this.temperature * 9.0 / 5.0 + 32.0);
                                        sufix = "°F";
                                        break;
                                }
                                icon_img = "temperature-high";
                                break;
                            case 1:
                                val = this.humidity;
                                icon_img = "tint";
                                sufix = "%";
                                break;
                            case 2:
                                switch (this.config.pressureScaleType) {
                                    case 0: // hPa
                                        val = this.pressure;
                                        sufix = " hPa";
                                        break;
                                    case 1: // inHg
                                        val = Math.round(this.pressure * 100 / 33.864) / 100;
                                        sufix = " inHg";
                                        break;
                                }
                                icon_img = "tachometer-alt";
                                break;
                        }
            
                        var tr = document.createElement('tr');
                        var icon = document.createElement("i");
            
                        icon.className = 'fa fa-' + icon_img + ' bme-icon';
            
                        var text_div = document.createElement("div");
                        var text = document.createTextNode(" " + val + sufix);
                        text_div.className = 'bme-text';
                        text_div.appendChild(text);
            
                        var td = document.createElement('td');
                        td.className = 'bme-td-icon';
                        td.appendChild(icon)
                        tr.appendChild(td)
            
                        var td = document.createElement('td');
                        td.appendChild(text_div)
                        tr.appendChild(td)
            
                        tbdy.appendChild(tr);
                    }
                    table.appendChild(tbdy);
                    wrapper.appendChild(table);
            
                    return wrapper;
                },
            
                socketNotificationReceived: function (notification, payload) {
                    if (notification === 'DATA') {
                        this.temperature = payload.temp;
                        this.humidity = payload.humidity;
                        this.pressure = payload.press;
                        this.updateDom();
                    }
                },
            });
            
            S R 2 Replies Last reply Reply Quote 0
            • S Offline
              sdetweil @JohnGalt
              last edited by

              @JohnGalt the module also has a node_helper.js , this is where the python script is launched

              browsers cannot access hardware or files directly (for security reasons)

              Sam

              How to add modules

              learning how to use browser developers window for css changes

              J 1 Reply Last reply Reply Quote 0
              • J Offline
                JohnGalt @sdetweil
                last edited by

                @sdetweil – Hi Sam, thanks for looking in on this.

                I guess I don’t understand… If the module is calling a python script, and the script is polling the sensor - then it would seem to me that the browser isn’t accessing the hardware or files directly. Obviously I’m missing something here.

                S 1 Reply Last reply Reply Quote 0
                • S Offline
                  sdetweil @JohnGalt
                  last edited by

                  @JohnGalt the browser (electron) wants to display the data from the sensor, but it cant read it directly. so the module sends a request to the helper to get the data from device 0x38

                  the module uses a python script to get the data
                  the python script is reporting an error

                  that is what needs to be looked at.

                  you posted the code from the module/browser side which is not involved in getting the actual data

                  Sam

                  How to add modules

                  learning how to use browser developers window for css changes

                  J 1 Reply Last reply Reply Quote 0
                  • R Offline
                    rkorell @JohnGalt
                    last edited by rkorell

                    the python script you are looking for is bme280.py

                    #!/usr/bin/python
                    #--------------------------------------
                    #    ___  ___  _ ____
                    #   / _ \/ _ \(_) __/__  __ __
                    #  / , _/ ___/ /\ \/ _ \/ // /
                    # /_/|_/_/  /_/___/ .__/\_, /
                    #                /_/   /___/
                    #
                    #           bme280.py
                    #  Read data from a digital pressure sensor.
                    #
                    #  Official datasheet available from :
                    #  https://www.bosch-sensortec.com/bst/products/all_products/bme280
                    #
                    # Author : Matt Hawkins
                    # Date   : 21/01/2018
                    #
                    # https://www.raspberrypi-spy.co.uk/
                    #
                    #--------------------------------------
                    import smbus
                    import sys
                    import time
                    from ctypes import c_short
                    from ctypes import c_byte
                    from ctypes import c_ubyte
                    
                    DEVICE = 0x76 # Default device I2C address
                    
                    try: #override device address like '0x77'
                        DEVICE = int(sys.argv[1], 16)
                    except:
                        pass
                    
                    bus = smbus.SMBus(1) # Rev 2 Pi, Pi 2 & Pi 3 uses bus 1
                                         # Rev 1 Pi uses bus 0
                    
                    def getShort(data, index):
                      # return two bytes from data as a signed 16-bit value
                      return c_short((data[index+1] << 8) + data[index]).value
                    
                    def getUShort(data, index):
                      # return two bytes from data as an unsigned 16-bit value
                      return (data[index+1] << 8) + data[index]
                    
                    def getChar(data,index):
                      # return one byte from data as a signed char
                      result = data[index]
                      if result > 127:
                        result -= 256
                      return result
                    
                    def getUChar(data,index):
                      # return one byte from data as an unsigned char
                      result =  data[index] & 0xFF
                      return result
                    
                    def readBME280ID(addr=DEVICE):
                      # Chip ID Register Address
                      REG_ID     = 0xD0
                      (chip_id, chip_version) = bus.read_i2c_block_data(addr, REG_ID, 2)
                      return (chip_id, chip_version)
                    
                    def readBME280All(addr=DEVICE):
                      # Register Addresses
                      REG_DATA = 0xF7
                      REG_CONTROL = 0xF4
                      REG_CONFIG  = 0xF5
                    
                      REG_CONTROL_HUM = 0xF2
                      REG_HUM_MSB = 0xFD
                      REG_HUM_LSB = 0xFE
                    
                      # Oversample setting - page 27
                      OVERSAMPLE_TEMP = 2
                      OVERSAMPLE_PRES = 2
                      MODE = 1
                    
                      # Oversample setting for humidity register - page 26
                      OVERSAMPLE_HUM = 2
                      bus.write_byte_data(addr, REG_CONTROL_HUM, OVERSAMPLE_HUM)
                    
                      control = OVERSAMPLE_TEMP<<5 | OVERSAMPLE_PRES<<2 | MODE
                      bus.write_byte_data(addr, REG_CONTROL, control)
                    
                      # Read blocks of calibration data from EEPROM
                      # See Page 22 data sheet
                      cal1 = bus.read_i2c_block_data(addr, 0x88, 24)
                      cal2 = bus.read_i2c_block_data(addr, 0xA1, 1)
                      cal3 = bus.read_i2c_block_data(addr, 0xE1, 7)
                    
                      # Convert byte data to word values
                      dig_T1 = getUShort(cal1, 0)
                      dig_T2 = getShort(cal1, 2)
                      dig_T3 = getShort(cal1, 4)
                    
                      dig_P1 = getUShort(cal1, 6)
                      dig_P2 = getShort(cal1, 8)
                      dig_P3 = getShort(cal1, 10)
                      dig_P4 = getShort(cal1, 12)
                      dig_P5 = getShort(cal1, 14)
                      dig_P6 = getShort(cal1, 16)
                      dig_P7 = getShort(cal1, 18)
                      dig_P8 = getShort(cal1, 20)
                      dig_P9 = getShort(cal1, 22)
                    
                      dig_H1 = getUChar(cal2, 0)
                      dig_H2 = getShort(cal3, 0)
                      dig_H3 = getUChar(cal3, 2)
                    
                      dig_H4 = getChar(cal3, 3)
                      dig_H4 = (dig_H4 << 24) >> 20
                      dig_H4 = dig_H4 | (getChar(cal3, 4) & 0x0F)
                    
                      dig_H5 = getChar(cal3, 5)
                      dig_H5 = (dig_H5 << 24) >> 20
                      dig_H5 = dig_H5 | (getUChar(cal3, 4) >> 4 & 0x0F)
                    
                      dig_H6 = getChar(cal3, 6)
                    
                      # Wait in ms (Datasheet Appendix B: Measurement time and current calculation)
                      wait_time = 1.25 + (2.3 * OVERSAMPLE_TEMP) + ((2.3 * OVERSAMPLE_PRES) + 0.575) + ((2.3 * OVERSAMPLE_HUM)+0.575)
                      time.sleep(wait_time/1000)  # Wait the required time  
                    
                      # Read temperature/pressure/humidity
                      data = bus.read_i2c_block_data(addr, REG_DATA, 8)
                      pres_raw = (data[0] << 12) | (data[1] << 4) | (data[2] >> 4)
                      temp_raw = (data[3] << 12) | (data[4] << 4) | (data[5] >> 4)
                      hum_raw = (data[6] << 8) | data[7]
                    
                      #Refine temperature
                      var1 = ((((temp_raw>>3)-(dig_T1<<1)))*(dig_T2)) >> 11
                      var2 = (((((temp_raw>>4) - (dig_T1)) * ((temp_raw>>4) - (dig_T1))) >> 12) * (dig_T3)) >> 14
                      t_fine = var1+var2
                      temperature = float(((t_fine * 5) + 128) >> 8);
                    
                      # Refine pressure and adjust for temperature
                      var1 = t_fine / 2.0 - 64000.0
                      var2 = var1 * var1 * dig_P6 / 32768.0
                      var2 = var2 + var1 * dig_P5 * 2.0
                      var2 = var2 / 4.0 + dig_P4 * 65536.0
                      var1 = (dig_P3 * var1 * var1 / 524288.0 + dig_P2 * var1) / 524288.0
                      var1 = (1.0 + var1 / 32768.0) * dig_P1
                      if var1 == 0:
                        pressure=0
                      else:
                        pressure = 1048576.0 - pres_raw
                        pressure = ((pressure - var2 / 4096.0) * 6250.0) / var1
                        var1 = dig_P9 * pressure * pressure / 2147483648.0
                        var2 = pressure * dig_P8 / 32768.0
                        pressure = pressure + (var1 + var2 + dig_P7) / 16.0
                    
                      # Refine humidity
                      humidity = t_fine - 76800.0
                      humidity = (hum_raw - (dig_H4 * 64.0 + dig_H5 / 16384.0 * humidity)) * (dig_H2 / 65536.0 * (1.0 + dig_H6 / 67108864.0 * humidity * (1.0 + dig_H3 / 67108864.0 * humidity)))
                      humidity = humidity * (1.0 - dig_H1 * humidity / 524288.0)
                      if humidity > 100:
                        humidity = 100
                      elif humidity < 0:
                        humidity = 0
                    
                      return temperature/100.0,pressure/100.0,humidity
                    
                    def main():
                    
                      # (chip_id, chip_version) = readBME280ID()
                      # print("Chip ID     :", chip_id)
                      # print("Version     :", chip_version)
                    
                      temperature,pressure,humidity = readBME280All()
                    
                      print(round(temperature,1),round(humidity,1),round(pressure,1))
                    
                    if __name__=="__main__":
                       main()
                    

                    @JohnGalt said in AHT20 Humidity + Temperature Sensor:

                    Remote I/O error

                    The given error seems to by not a program but an I/O problem.
                    I’m not familiar with this sensor so I do not know how to connect and - most important - how to figure out the right “deviceAddress” - it seems that there is the error located.

                    Either the address isn’t the correct one or the IO channel is somehow broken.
                    For the latter came in my mind: if this is a I2C conected device - do you have enabled I2C on your Raspi?

                    I’ve tried to “understand” what happens in the python script above as well as in the C-exmaple program on the Bosch product page for bme280 sensor, but didn’t got it…

                    Regards,
                    Ralf

                    R J 3 Replies Last reply Reply Quote 0
                    • R Offline
                      rkorell @rkorell
                      last edited by rkorell

                      @JohnGalt
                      just seen while re-reading my last posting:

                      nodehelper.js (the part of the module which is communicating with the python program and so with the sensor) is calling python3 :

                      exec(`python3 ./modules/MMM-BME280/bme280.py ${deviceAddr}`, (error, stdout) => {
                      

                      but the python script itself is referencing python 2 (see above post, source code of bme280.py, 1st line:

                      #!/usr/bin/python
                      

                      I guess this must match and doesn’t …
                      So may this is the cause of your problems.

                      And if this is true it is may really hard to get this working because you may run in several incompatibilities and library-conflicts …

                      Regards,
                      Ralf

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                      • J Offline
                        JohnGalt @sdetweil
                        last edited by

                        @sdetweil – Thanks, Sam. It looks like I intended to send bme280.py but actually copied MMM-BME280.js. I see below where Ralf did post it, so I will look at that, too.

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