| title | layout | meta-description | share | author | about | cats | simple-description | acknowledgements |
|---|---|---|---|---|---|---|---|---|
8x8 LED Matrix |
text-width-sidebar |
Connect a DS3231 RTC to the microbit and take time & date with python. |
true |
jez |
Use 8x8 LED matrix with HK16K33 driver |
external |
HD44780 LCD + Backpack |
Messy LED Matrix image by Hypercoregz on Flickr (CC-BY). Teaser Image by Adafruit (CC-BY). |
LCD displays are a good way to display information from the microbit; it is much easier to read than the scrolling display.
(picture)
As with the 8x8 matrix, an I2C backpack is used for simplicitiy.
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The LCD screen above has two roads of 16 characters (16x2). There is a Hitachi HD44780 chip on the back of the module which drives the display. These are usually listed as HD44780 LCDs.
The backpack connects to the LCD module's 16 pins. The microbit communicates display information over two I2C wires as opposed to 4 or 8!
There are many available and are usually around £3. Here's an example on eBay.
The contrast is altered by pin3 on the HD44780.
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A microbit edge connector is required to access the I2C pins on the microbit. These are pin19 and pin20 of the microbit.
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| Backpack Pin | Microbit Pin |
|---|---|
GND |
GND |
VCC+ |
3V |
DAT or SDA |
PIN 20 |
CLK or SCA |
PIN 19 |
The I2C naming conventions are different than usual. SCL = CLK & SDA = DAT.
The I2C bus is accessed through pin19 and pin20. There are already two components on the bus:
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| Device | I2C Address |
|---|---|
| Accelerometer | 0x1D |
| Magnetometer | 0x0E |
Each slave on the bus must occupy a different address. Check the I2C address on the data sheet of your component and ensure they do not conflict with other components. On the Adafruit backpack it's possible to change the I2C address if required.
The is a guide to scanning the I2C bus on this website.
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Radomir Dopieralski has written a Python module to control HT16K33-based backpacks. Download the HT16k33 driver and save it to your computer.
Upload the saved module to the microbit in mu. See here for tutorial on how to add modules.
{% highlight python %} from microbit import i2c, sleep
from ht16k33 import Matrix8x8
display = Matrix8x8(i2c)
for x in range(8): for y in range(8): display.pixel(x, y, 1) display.show() sleep(50)
display.fill(0x00) display.show() sleep(1000)
display.fill(0xff) display.show() sleep(1000)
for x in range(15): display.brightness(x) sleep(50)
{% endhighlight %}
The MAX7219 is an alternative driver that uses SPI. Multiple LED displays can be linked together. I've not managed to slim a module down yet for the microbit.