Connect units to PbHUB



  • I am trying to connect a LIGHT and an EARTH unit to the PbHUB. I connected the PbHUB to PortA, the EARTH sensor to Hub 0 and the LIGHT sensor to Hub 1.

    0_1568885495578_IMG_3717.JPG

    My code looks like this:

    pbhub = unit.get(unit.PBHUB, unit.PORTA)
    earth = pbhub.analogRead(0x00)
    light = pbhub.analogRead(0x01)
    

    I am able to read values from both sensors, however with strange behaviours. E.g. the lux value increases when it gets darker and vice versa. I guess the problem is, that I am lacking the logic of the analogRead function in the LIGHT and EARTH units:
    https://github.com/m5stack/UIFlow-Code/blob/a0dbef98fe29323d6b1837b479764fdab50c3836/units/_light.py
    https://github.com/m5stack/UIFlow-Code/blob/a0dbef98fe29323d6b1837b479764fdab50c3836/units/_earth.py

    However I do not see how I would have to connect this unit correctly to the PbHUB. Do I have to copy paste the analogRead logic or is there another way to connect these units?
    @ajb2k3 Do you know how this should be handled?


  • M5Stack

    Hey I made a video on the PBHUB https://www.youtube.com/watch?v=NG9SBKfxX5w maybe it can help you. Often when I want to write some micropython code I make it in Uiflow first. Since the micropython documentation is lacking this is a good way to find out what might be missing from your code and what the micropython commands you need are.



  • @maechler You caught me here at a loss. Check out @lukasmaximus video on youtube.



  • @lukasmaximus @ajb2k3 Thanks for your support! Although the video does not really answer my question.

    I am able to read values from the PbHUB like this:

    pbhub = unit.get(unit.PBHUB, unit.PORTA)
    earth = pbhub.analogRead(0x00)
    light = pbhub.analogRead(0x01)
    

    The problem is, that these values seem to be wrong. The lux value increases when it gets darker, similarly the earth unit says the earth gets dryer when it actually gets wetter. I think the problem is, that reading directly from PbHUB, the logic from the LIGHT.analogValue function is missing:

    class Light:
        @property
        def analogValue(self):
            data = 0
            max = 0
            min = 4096
            for i in range(0, 10):
                newdata = 4095 - self.adc.readraw()
                data += newdata
                if newdata > max:
                    max = newdata
                if newdata < min:
                    min = newdata
            data -= (max + min)
            data >>= 3
            return round(1024 * data / 4095, 2)
    

    This function seems to transform the data in a way that is missing when reading the value directly from PbHUB. My question is whether I do have to copy paste this logic or whether there is some way to reuse the LIGHT unit with PbHUB?

    I would like to be able to do something like this:

    pbhub = unit.get(unit.PBHUB, unit.PORTA)
    earth = unit.get(unit.EARTH, pbhub.HUB0) # Not M5Stack API yet
    light = unit.get(unit.LIGHT, pbhub.HUB1) # Not M5Stack API yet
    
    # This should read the value correctly, using the `LIGHT.analogValue` logic
    print(earth.analogValue())
    print(light.analogValue()) 
    


  • I think the Python code in these units was not implemented with PbHUB in mind at all. I agree with your suggested interface will be very useful. You can probably do this by deriving a HubAwareLight class from Light. The job of HubAwareLight is to just set newdata value in Light



  • @maechler are you saying the values are inverted?



  • @ws1088 Thanks for the clarification!
    Do you say that the value I get with pbhub.analogRead(0x00) should be plugged in for newdata in Light.analogValue?
    I would have placed it where the Light unit calls self.adc.readraw().
    Do I also have to call pbhub.analogRead(0x00) 10 times in a loop, as the Light unit does?

    @ajb2k3 Yes, kind of. I have tested what the Light unit does for increasing values of self.adc.readraw() it will output decreasing values. This inversion is missing when reading directly from PbHUB.

    class Light:
        @staticmethod
        def analogValue(value):
            data = 0
            max = 0
            min = 4096
            for i in range(0, 10):
                newdata = 4095 - value
                data += newdata
                if newdata > max:
                    max = newdata
                if newdata < min:
                    min = newdata
            data -= (max + min)
            data >>= 3
    
            return round(1024 * data / 4095, 2)
    
    
    print(400, Light.analogValue(400))  # 400 923.98
    print(500, Light.analogValue(500))  # 500 898.97
    print(600, Light.analogValue(600))  # 600 873.96
    print(700, Light.analogValue(700))  # 700 848.96
    print(800, Light.analogValue(800))  # 800 823.95
    print(900, Light.analogValue(900))  # 900 798.95
    


  • I ended up copy pasting the method from the Light unit with some slight adjustments:

    def pbhubAnalogRead(pbhub, pbhub_address):
            data = 0
            max_val = 30
            min_val = 750
            for i in range(0, 10):
                newdata = 750 - pbhub.analogRead(pbhub_address)
                data += newdata
                if newdata > max_val:
                    max_val = newdata
                if newdata < min_val:
                    min_val = newdata
            data -= (max_val + min_val)
            data >>= 3
            return round(max(1024 * data / 750, 0), 2)
    
    pbhub = unit.get(unit.PBHUB, unit.PORTA)
    light = pbhubAnalogRead(pbhub, 0x01)
    

    The magic number min_val I got by pressing my finger on the light sensor (blocking all the light from entering) and reading the analog value. The value 750 seems to be the minimum value the light sensor would emit. The number max_val I got by pointing a strong light at the sensor, it seems to be the maximum value the sensor emits. The min max values are mixed up because it measures the resistance and decreasing resistance means increasing light intensity. Using this method I get values that are somewhat similar to what I get by connecting the Light unit to PortB directly.

    If anyone knows how this should be done properly, please let me know!