11x7 LED Matrix on Pico, noob help please


I want to get the 11x7 LED Matrix breakout running on a Pico. Seems this should take less than 5 mins but as a complete beginner I got stuck. There is obviously something super simple that I have missed.

I am powering the Pico only via a USB data cable and have succeeded in getting the “blink” program to flash the onboard LED, so I guess that means the board is OK. I have connected the LED breakout power pins to the VSYS and GND pads and the I2C SDA/SCL to pins 4 and 5 respectively. I checked with a multimeter that I am getting around 4,8V on the breakout supply terminals. I followed the “Getting started with Raspberry Pi Pico” guide and have loaded the pimoroni-pico-v1.19.10-micropython.uf2 firmware onto the Pico using Thonny. On the info page for the LED matrix there is a link to some examples in micropython. I followed the link and installed the “demo.py” for the 11x7 LED matrix breakout. The program executes from Thonny without error, but nothing happens on the matrix. What have I done wrong ?

Make sure your using the same i2c pins in code that you have it wired up too.
And that you have used the correct pins, physical number versus GPIO number.
The example is using the GPIO number.
Raspberry Pi Pico GPIO Pinout

Thanks for the reply. The pinout map is very helpful.

The “demo.py” file for the 11x7 matrix contains the following lines concerning I2C setup:

PINS_BREAKOUT_GARDEN = {“sda”: 4, “scl”: 5}
PINS_PICO_EXPLORER = {“sda”: 20, “scl”: 21}

matrix = BreakoutMatrix11x7(i2c)

My interpretation here is that pins 4 and 5 should be used for SDA and SCL respectively. However I am not using the Breakout Garden or Pico Explorer, just the bare Pico board so am not certain these are the right pins. Which pins should I be using ?

I just re-read your post and saw that the numbers relate to the GPIO number, not the pin number. I changed the pin numbers in the code to 2 and 3 for SDA and SCL respectively and saw the light! :-)

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Good to hear that you got it working. I had a hunch it was a Pin number versus GPIO number issue. Easy mistake to make. Been there done that. ;)