encants-dots

Small DIY project to play with a 8x8 dot matrix display and a simple microcontroller board.

Bill Of Materials

• 8x8 dot matrix display with MAX7219
• ESP32-S2-Saola-1 board
• VS Code with PlatformIO
• LedControl library

Physical Setup

Microcontroller to display connection

The source code uses these microcontroller pins, defined in the Dots.cpp file:

• 17 for the display data pin
• 16 for the display chip selector pin
• 15 for the display clock pin If it's no possible to plug the display directly in the microcontroller, it will require 3 breadboard-like small cables to connect both.

Microcontroller to PC connection

Any appropriate USB to USB cable, depending on the ports types, should work.

Windows + WSL2 Setup

Part of the fun is to play with the WSL2 environment on Windows and see how easy/hard is to use it to work with microcontrollers like that, which is connected via USB.

But after going through the right instructions, it's actually pretty straightforward: https://learn.microsoft.com/en-us/windows/wsl/connect-usb

After the usbipd command setup, simply use the following commands on a Windows Terminal to find the right connected USB device and attach it to the running WSL instance.

PS C:\Users\Sergio> usbipd wsl list
BUSID  VID:PID    DEVICE                   STATE
1-1    1a86:7523  USB-SERIAL CH340 (COM3)  Not attached

PS C:\Users\Sergio> usbipd wsl attach --busid 1-1
usbipd: info: Using default WSL distribution 'Ubuntu'; specify the '--distribution' option to select a different one.

PS C:\Users\Sergio> usbipd wsl list
BUSID  VID:PID    DEVICE                   STATE
1-1    1a86:7523  USB-SERIAL CH340 (COM3)  Attached - Ubuntu

And, from a WSL Terminal, make sure that it appears as connected, and it has the right access permissions, or update them otherwise (I assume this step can be automated but I haven't spent extra time on it yet).

~/dev/projects/encants-dots » ls -al /dev/ttyUSB*                                                                     
crw------- 1 root root 188, 0 May 26 11:15 /dev/ttyUSB0

~/dev/projects/encants-dots » sudo chmod 666 /dev/ttyUSB0                                                                     

~/dev/projects/encants-dots » ls -al /dev/ttyUSB*                                                                     
crw-rw-rw- 1 root root 188, 0 May 26 11:15 /dev/ttyUSB0

Usage

With all the setup completed,

1. Build the code
2. Upload it to the microcontroller
3. Change the code at will, and repeat from 1.

Embedded Web Server

TBD

Troubleshooting

Error message .pio/libdeps/esp32-s2-saola-1/LedControl/src/LedControl.h:30:10: fatal error: avr/pgmspace.h: No such file or directory

Edit the LedControl.h file and change

#include <avr/pgmspace.h>

to

#include <pgmspace.h>

Proper PlatformIO platform missing or invalid

Try reinstalling the platform from PlatformIO, in this case the Espressif 32 platform.

Fun Fact

The name encants-dots is a combination of dots from the obvious fact that the display is a 8x8 dot matrix, and encants from the fact that I got that display for few Euro-cents at the most famous flea market in Barcelona: Mercat dels Encants

Enjoy!