Using the Micro:bit Radio to Send and Receive Sensor Data

In this blog post I’m going to demonstrate the micro:bits radio capability. Have you ever wanted to know how cold your fridge is? Well I thought it would be interesting to find out so we took the following parts and got tinkering!

2 x micro:bit
1 x micro:pixel
1 x 1000mAh LiPo
1 x 6000mAh LiPo
3 x Alligator cables
1 x TMP36 sensor breakout

We then got to the programming, we did this in python and I use mu for the coding. You can download the code here.

The transmitter:bit

In this code we read the voltage from the TMP36 and convert this into the temperature then display it on the LED display and if a micro pixel is attached to this unit it will also change the colour depending on the temperature. We then switch on the radio and send the temperature as a string to any listening micro:bits then switch the radio off.

TempSendColour.py

#   Read and display the temperature
#   and update the NeoPixel panel with 
#   a colour between Blue and Red, and
#   send the data to any listening node 
#   (The micro:pixel panel is not needed)
#   for WWW.proto-pic.co.uk by Drew Anderson

#   import the libraries required by the microbit
from microbit import *
#   import the libraries required by the micro:pixel and Radio
import neopixel
import radio

#   We have 8x4 pixels, 32 in total on pin 0
np = neopixel.NeoPixel(pin0, 32)

while True:
    # Read the RAW temperature
    tmp = pin1.read_analog()
    # Convert the RAW to a real Temperature
    temp = ((tmp * (3300.0/1024.0))-500.0)/10.0
    # Expand the scale for better display in micro:pixel
    tempcolour = int((temp * 3.6))
    # The next 4 lines constrain the colour value to 0 <> 127
    if (tempcolour < 0):
        tempcolour = 0
    if (tempcolour > 127):
        tempcolour = 127
    # Show the colour on the micro:pixel
    for pix in range (0 , 32):
        np[pix] = (tempcolour,0,(255-(tempcolour*2)))
    np.show()
    # Show the Temperature to one decimal place
    tempToShow = "{0:0.1f}".format(temp)
    display.scroll(tempToShow)
    # Turn on the radio
    radio.on()
    # Send the temp as a string
    radio.send(str(temp))
    # Let the data finish
    sleep(50)
    # Turn off the radio to save battery
    radio.off()
sleep(50)

The receiver:bit

In this code we set up the micro:pixel then switch on the radio, once we've done this we listen for a signal and then take the string we receive and convert it to a float. Once we have that we do a little maths to increase the scale. We then display the temperature on the LED matrix and change the colour of the micro:bit depending on the temperature.

TempReceiveColour.py

#   Receive and display the temperature
#   and update the NeoPixel panel with 
#   a colour between Blue and Red
#   for WWW.proto-pic.co.uk by Drew Anderson

#   import the libraries required by the microbit
from microbit import *
#   import the libraries required by the micro:pixel board & Radio
import neopixel
import radio
#   We have 8x4 pixels - 32 in total on pin 0
np = neopixel.NeoPixel(pin0, 32)
#   Turn the radio transmitter on (Required)
radio.on()

while True:
    # Read any incoming Data
    inData = radio.receive()
    if inData is not None:
        # inData is a string - We want a float
        temp = float(inData)
        # A little bit of maths to extend the scale a bit
        tempcolour = int((temp * 3.6))
        # The next 4 lines constrain the value to between 0 and 127
        if (tempcolour < 0):
            tempcolour = 0
        if (tempcolour > 127):
            tempcolour = 127
        # Update the micro:pixel 
        for pix in range (0 , 32):
            np[pix] = (tempcolour,0,(255-(tempcolour*2)))
        np.show()
        # Show the temperature to 1 decimal place
        tempToShow = "{0:0.1f}".format(temp)
display.scroll(tempToShow)

Hook up guide:

First up slide one of the micro:bits into your micro:pixel.

Next up connect the larger capacity LiPo to the micro:bit.

We then connect up the TMP36 up to the other micro:bit 3V to VCC, GND to GND and Pin1 to TMP.

Finally we plug in the small LiPo into this micro:bit and you're all done!

In action video:

LINKS:

Mu micropython editor

Example code