Getting Started with Interstate 75
Interstate 75 is a RP2040-powered driver board for HUB75-style panels - the LED matrix panels that you sometimes see making up big fancy billboards or scrolling LED signage. We've made it so it can slot tidily into the back of a panel, with minimal extra hardware required. You can also now get an Interstate 75 W which has wireless internet connectivity, courtesy of Raspberry Pi Pico W Aboard!
This tutorial will show you how to plug things in and how to start making things light up, and it includes basic getting started instructions for both MicroPython and CircuitPython.
⚠ These code examples and instructions have been updated to work with Interstate 75 W and PicoGraphics.
What you'll need
- An Interstate 75 or Interstate 75 W
- A USB cable for programming (USB-C for Interstate 75, USB micro-B for Interstate 75 W )
- One (or more) RGB LED matrix panels
- If your project involves multiple panels, lots of brightness or you just want to run it untethered from your computer, you'll need an external 5v power supply attached to Interstate 75's screw terminals. An easy way to breakout wires from a barrel jack power supply is with a screw terminal block (the kind with a socket).
Power
You can power Interstate 75 and attached panels either through the screw terminals or (if you're drawing a modest amount of power) via the USB connector. LED matrix panels are hungry beasties - officially a 64x64 panel can consume up to 4 amps of electricity. Unofficially, you will probably get away with a lot less ampage than this if you're using it for things like displaying text or numbers and not driving the panels hard - we've had our examples running on four 64x64 panels from a 2A supply.
If your panels are in need of a power supply upgrade you might see glitching, flickering or find your Interstate 75 is constantly rebooting.
Connecting up one panel
For this tutorial, we're going to assume that you have a single panel and you're powering everything through the USB-connector on Interstate 75.
If your project involves multiple panels, it's probably a good idea to start off hooking up a single panel initially to make sure everything's working.
HUB75 panels have 16 pin data in and data out connectors on the back - you'll need to plug Interstate 75 into the data in connector. The backs of the panels should all have arrow markings which you can use to see the direction in which the data should be flowing through the panel.
Here are the backs of the panels we stock with the data in connector marked in red. Markings and layouts may vary slightly from batch to batch!
Go ahead and plug the pre-soldered socket header on Interstate 75 into the data in connector on your panel. The data connector has a nubbin on one side of it so you can only plug it in one way.
Connecting the power cable
The 16-pin connector on Interstate 75 will only provide a data signal to the panel, it won't provide it with enough electricity to power it. To power the panel, you'll need to connect it up to the screw connectors on Interstate 75, using the red and black power cable that comes with the panel. Loosen up the screws and slot the fork in-between the screw and the metal post, then tighten up the screws and give the wires a little tug to check they're securely held in place. Make sure you have the polarity correct - red to + and black to -.
The other end of the cable has a white plug on it - plug this to the power connector on your panel (marked 'power' on some panels, or just VCC and GND on others). The clippy part of this connector means it should also only go in one way round, though there's no harm in double checking that the red wires go into VCC and the black wire is connected to GND.
We've also attached the little magnetic feet that you get with the panel - they're useful if you want to stick your project to a metal surface like a noticeboard or your fridge.
Connecting up multiple panels
We're not going to go a huge amount of detail about chaining multiple panels in this tutorial but you can use the grey ribbon cables that come with the panels to do this - just plug one end of this cable into the vacant data out connector on the first panel, and the other end into the data in connector of the next panel into the chain.
Each panel will need powering, so you'll either have to connect another fork connector to the screw terminals or come up with some sort of custom wiring harness arrangement, like the double ended cable power cable in the photo below. We used some bits of Lego and M3 12mm screws to fasten these two 64x64 panels together, which makes for a nice rigid join that would be easy to expand into a little stand.
If you're using more than one panel we'd recommend hooking up an external power supply whilst you program Interstate 75 (or disconnecting power from the panels). However, modern computers and power supplies should have circuitry to protect themselves from USB over-current mishaps and we've not had any problems powering Interstate and a panel or two from our computer.
Note that if you're using MicroPython/PicoGraphics it only currently supports chained panels arranged next to each other in a line - you can find a list of sizes of matrices that are supported at the link below.
MicroPython and Interstate 75
The LED matrix drivers in our C++/MicroPython build make use of RP2040's programmable IOs and DMA to update the LEDs quickly in the background, minimising CPU usage and maximising colour depth. Our library will let you set individual pixels to a RGB colour value.
You can also now use our tiny graphics library PicoGraphics on your Interstate 75, which gives you a simple way of getting text, shapes and even images onto your LED matrix. The code below should work on both Interstate 75 and Interstate 75 W.
Installing our custom MicroPython build
Interstate 75 comes without firmware, so you'll need to install MicroPython as your first order of business. If you're brand new to Raspberry Pi Pico/RP2040s, you might find the step by step instructions in our Getting Started with Raspberry Pi Pico tutorial useful - it will show you how to install our custom MicroPython build and goes into more detail about how to use Thonny . Here's a quick TLDR!
- Download the most recent MicroPython .uf2 from the Releases page of our pimoroni-pico Github repository. You'll want the
pico.uf2 for Interstate 75, or thepicow.uf2 for Interstate 75 W. - Hold down the BOOT button of Interstate 75 (or BOOTSEL on Interstate 75 W), and then press, and release, the RESET button. This will put it into bootloader mode, and it should appear as a drive on your computer called RPI-RP2.
- Copy the .uf2 file to the RPI-RP2 drive - once you've done that Interstate 75 will reboot running Pirate brand MicroPython (it won't show up as a drive anymore).
- Install Thonny
- Open up Thonny. Make sure the interpreter (shown in the box on the bottom right corner) is set to 'MicroPython (Raspberry Pi Pico)'. If everything's working as it should look something like this. The flashing cursor next to the >>> in the 'Shell' box tells you that Interstate 75 is talking to your computer and is ready to accept instructions!
If you're having trouble using Thonny to communicate with your board, there's some troubleshooting suggestions at the link below:
Running the examples
You can find the MicroPython examples here - the generic examples are good to start with as they don't need any dependencies. If you click on the raw button it makes it easy to copy and paste them into the top box in Thonny. Press the green run button in the toolbar to run the code!
The examples in the 75W directory use Interstate 75 W's wireless functions and may require extra files to be installed. You can find WIFI_CONFIG.py and network_manager.py in examples/micropython/common.
Using PicoGraphics
As of early 2022 you can now use PicoGraphics (our inhouse tiny graphics library) with Interstate 75, woo! Here's how to get started.
Before you do anything else you'll need to import the interstate75 library - this library includes a bunch of helpful shortcuts for working with the functions on the Interstate board. Start your code off like this - you can either copy and paste this code into a new tab in Thonny and press the run button when it's complete, or enter it line by line in the REPL (that's the bottom box with the >>> prompt in it).
from interstate75 import Interstate75
i75 = Interstate75(display=Interstate75.DISPLAY_INTERSTATE75_64X64)
graphics = i75.display
i75 is our board - so we'll be using that when we want to do something physical with the board functions, like reading a button or updating the matrix. We need to specify what size matrix we have - we're using a 64 x 64 matrix but there's a list of other sizes you can use on the page below.
graphics is our graphics buffer - we'll be using that when we want to use one of our fancy PicoGraphics functions like drawing a shape, changing pen colour or drawing some text.
Lighting up the onboard RGB LED
You can light up Interstate 75's onboard RGB LED red like this:
i75.set_led(255, 0, 0)
The three numbers after set_led are an RGB (Red Green Blue) colour code, and each number should be between 0-255.
Using the buttons
Here's a simple example of how to do stuff with the buttons, using the functions in interstate75. This example makes the RGB LED light up red when you press the A button or green when you press the B button (on Interstate 75 W) or the BOOT button (on Interstate 75).
from interstate75 import Interstate75, SWITCH_A, SWITCH_B
i75 = Interstate75(display=Interstate75.DISPLAY_INTERSTATE75_64X64)
graphics = i75.display
while True:
if i75.switch_pressed(SWITCH_A):
i75.set_led(255, 0, 0)
elif i75.switch_pressed(SWITCH_B):
i75.set_led(0, 255, 0)
(you could also use SWITCH_BOOT to reference the button on Interstate 75 if you prefer, but you don't need to - our module should figure out which board you have automatically).
Lighting up the matrix
PicoGraphics keeps track of colours by using pens. If we want to draw something, we'll first need to set up a pen colour. As with the LED, the colour is specified by an RGB colour value. Each colour can be represented by mixing a particular amount of Red, Green, and Blue, from 0 to 255, meaning that you can get over 16 million different colours!! As an example, pure red is 255, 0, 0 and white is 255, 255, 255.
from interstate75 import Interstate75
i75 = Interstate75(display=Interstate75.DISPLAY_INTERSTATE75_64X64)
graphics = i75.display
MAGENTA = graphics.create_pen(255, 0, 255)
Once we've created a pen we'll need to tell PicoGraphics to use it:
graphics.set_pen(MAGENTA)
Clearing the display after you've used set_pen will fill it with the current pen colour:
graphics.clear()
Once you've finished drawing with graphics commands, we can update the LED matrix like this:
i75.update(graphics)
Adding some text
You can draw multiple things to the graphics buffer before triggering a update - here's a little hello world program that uses a few different coloured pens:
from interstate75 import Interstate75
i75 = Interstate75(display=Interstate75.DISPLAY_INTERSTATE75_64X64)
graphics = i75.display
MAGENTA = graphics.create_pen(255, 0, 255)
BLACK = graphics.create_pen(0, 0, 0)
WHITE = graphics.create_pen(255, 255, 255)
graphics.set_pen(BLACK)
graphics.clear()
graphics.set_pen(MAGENTA)
graphics.text("hello", 1, 0, scale=1)
graphics.set_pen(WHITE)
graphics.text("world", 1, 6, scale=1)
i75.update(graphics)
When using the text function you'll need to specify the position the text is going to be on the screen. Pixels are organised by their x/y coordinates from the top left hand corner, so the top left pixel is 0, 0. Remember that, in Python, things are numbered from 0 rather than from 1.
Perhaps you'd like your message to flash? To do that we'll need to incorporate some time.sleep() commands to add some short pauses in our code, and put all the drawing code into a while True: loop, so it runs multiple times :
from interstate75 import Interstate75
import time
i75 = Interstate75(display=Interstate75.DISPLAY_INTERSTATE75_64X64)
graphics = i75.display
MAGENTA = graphics.create_pen(255, 0, 255)
BLACK = graphics.create_pen(0, 0, 0)
WHITE = graphics.create_pen(255, 255, 255)
while True:
graphics.set_pen(MAGENTA)
graphics.text("hello", 1, 0, scale=1)
graphics.set_pen(WHITE)
graphics.text("world", 1, 6, scale=1)
i75.update(graphics)
time.sleep(0.5)
graphics.set_pen(BLACK)
graphics.clear()
i75.update(graphics)
time.sleep(0.5)
Congrats - you're well on the way to opening your own kebab shop!
You can find out more about the things you can do with PicoGraphics (including drawing shapes, illuminating individual pixels and even displaying jpegs) at the link below:
Lighting raw pixels on the matrix
If setting individual pixels is all you need for your application you might find using the raw hub75 module and its set_pixel function to be faster than using PicoGraphics.
import hub75
WIDTH = 64
HEIGHT = 64
matrix = hub75.Hub75(WIDTH, HEIGHT)
matrix.start()
matrix.set_pixel(0, 0, 255, 0, 0)
The first two digits are which pixel you want to update (0, 0 is the one in the top left corner) and the last three digits are the RGB colour code.
To clear any pixels that you've set, you can use the clear() function:
matrix.clear()
Find out more about the hub75 module at the link below.
MicroPython troubleshooting
We've found some matrix panels have hardware differences which may mean you need to tweak some settings. If you're getting a weird, glitchy top row on your matrix or if the right LEDs aren't lighting up, try initialising your matrix like this:
i75 = Interstate75(display=Interstate75.DISPLAY_INTERSTATE75_64X64, stb_invert=True)
If your matrix isn't lighting up at all when you run the examples (and if you aren't getting any errors in Thonny), first double check that Interstate 75 is plugged into the 'data in' connector on your matrix. If it is, it might be worth giving this option a go - some newer panels have a FM6216A driver chip that requires different register settings to work.
i75 = Interstate75(display=Interstate75.DISPLAY_INTERSTATE75_64X64, panel_type=Interstate75.PANEL_FM6126A)
The LEDs on our most recent batch of HUB75 panels have a different colour order to previous batches - fun! If your blue is coming out green and your green is coming out blue you can switch the order our library uses like this:
i75 = Interstate75(display=Interstate75.DISPLAY_INTERSTATE75_64X64, color_order=Interstate75.COLOR_ORDER_RBG)
Other colour orders are available, check the hub75 function reference for more info:
CircuitPython
CircuitPython drivers are designed to work on a bunch of different microcontrollers so you won't get the fancy RP2040-architecture specific tweaks that you'll find in our library. You will get access to Adafruit's mighty DisplayIO library though, which gives you lots of tools for displaying all sorts of different kinds of text, shapes and even simple images.
Installing CircuitPython and libraries
To install CircuitPython -
Download the Interstate 75 CircuitPython .uf2 (if you have a Interstate 75) or the Pico W .uf2 (if you have an Interstate 75 W). You'll probably also need the CircuitPython driver bundle (be sure to grab the one that matches the version of CircuitPython that you just downloaded)
Hold down the BOOT button of Interstate 75 (or BOOTSEL on Interstate 75 W), and then press, and release, the RESET button. This will put it into bootloader mode, and it should appear as a drive on your computer called RPI-RP2.
Copy the CircuitPython .uf2 to the RPI-RP2 drive. After a few seconds, it should reappear as a drive called CIRCUITPY.
With CircuitPython, you always save your code as
code.py, and it will run automatically. You don't need to use Thonny, you can editcode.pywith any text editor. Using Thonny or Mu as your editor is handy though, as it lets you view the serial console which can be useful for debugging error messages.
Running the examples
You can find some RGB matrix code examples in RGB LED Matrices with CircuitPython. To use them with Interstate 75 or Interstate 75 W, just point them at the right pins when initialising your matrix object. You'll need to do this differently for Interstate 75 and Interstate 75 W, as the pins have different names.
32 x 32 or 32 x 64 matrix (Interstate 75)
matrix = rgbmatrix.RGBMatrix(
width=64, height=32, bit_depth=3,
rgb_pins=[board.R0, board.G0, board.B0, board.R1, board.G1, board.B1],
addr_pins=[board.ROW_A, board.ROW_B, board.ROW_C, board.ROW_D],
clock_pin=board.CLK, latch_pin=board.LAT, output_enable_pin=board.OE)
64 x 64 (or bigger) matrix (Interstate 75)
matrix = rgbmatrix.RGBMatrix(
width=64, height=64, bit_depth=3,
rgb_pins=[board.R0, board.G0, board.B0, board.R1, board.G1, board.B1],
addr_pins=[board.ROW_A, board.ROW_B, board.ROW_C, board.ROW_D, board.ROW_E],
clock_pin=board.CLK, latch_pin=board.LAT, output_enable_pin=board.OE)
32 x 32 or 32 x 64 matrix (Interstate 75 W)
matrix = rgbmatrix.RGBMatrix(
width=64, height=32, bit_depth=3,
rgb_pins=[board.GP0, board.GP1, board.GP2, board.GP3, board.GP4, board.GP5],
addr_pins=[board.GP6, board.GP7, board.GP8, board.GP9],
clock_pin=board.GP11, latch_pin=board.GP12, output_enable_pin=board.GP13)
64 x 64 (or bigger) matrix (Interstate 75 W)
matrix = rgbmatrix.RGBMatrix(
width=64, height=64, bit_depth=3,
rgb_pins=[board.GP0, board.GP1, board.GP2, board.GP3, board.GP4, board.GP5],
addr_pins=[board.GP6, board.GP7, board.GP8, board.GP9, board.GP10],
clock_pin=board.GP11, latch_pin=board.GP12, output_enable_pin=board.GP13)
Using the buttons and LED
Here's a quick example of how to use Interstate 75's buttons and RGB LED in CircuitPython. You'll need to grab adafruit_rgbled.py and simpleio.mpy from the library bundle and pop them in your lib folder on CIRCUITPY.
For Interstate 75:
import board
import digitalio
import adafruit_rgbled
import busio
button_boot = digitalio.DigitalInOut(board.USER_SW)
button_boot.direction = digitalio.Direction.INPUT
button_boot.pull = digitalio.Pull.UP
button_a = digitalio.DigitalInOut(board.SW_A)
button_a.direction = digitalio.Direction.INPUT
button_a.pull = digitalio.Pull.UP
led = adafruit_rgbled.RGBLED(board.LED_R, board.LED_G, board.LED_B, invert_pwm = True)
def button_read(button):
return not button.value
while True:
if button_read(button_a):
led.color = (0, 255, 0)
if button_read(button_boot):
led.color = (0, 0, 255)
For Interstate 75 W:
import board
import digitalio
import adafruit_rgbled
import busio
button_a = digitalio.DigitalInOut(board.GP14)
button_a.direction = digitalio.Direction.INPUT
button_a.pull = digitalio.Pull.UP
button_b = digitalio.DigitalInOut(board.GP15)
button_b.direction = digitalio.Direction.INPUT
button_b.pull = digitalio.Pull.UP
led = adafruit_rgbled.RGBLED(board.GP16, board.GP17, board.GP18, invert_pwm = True)
def button_read(button):
return not button.value
while True:
if button_read(button_a):
led.color = (0, 255, 0)
if button_read(button_b):
led.color = (0, 0, 255)
If you're interested in learning how to do things with wi-fi in CircuitPython, check out the link below!
Next steps
Now that you know how to drive an LED matrix with a RP2040, how about hooking up a Breakout Garden breakout and using it to display sensor data, like temperature and humidity? You could attach an encoder and make an RGB Etch-A-Sketch. Or a real-time clock so that your giant holiday countdown timer keeps track of time when it's powered off?
Search above to find more great tutorials and guides.