Category: Raspbian

a rant about raspberry pi os

whbeebe

 

The Raspberry Pi OS desktop

I’m still trying to love Raspberry Pi OS and its LXDE-based window manager, and it’s just not happening. I’ve tweaked some things, even going so far as to pull a screen wallpaper from Linux Mint Uma (mikeu_red_waves.jpg); that seems to make the overall desktop experience a bit better for me.

I tried lxappearance to change the desktop. That application opened but I couldn’t change anything.

I then switched from Firefox as my default browser to Chromium because in spite of what was claimed, Firefox is still a hot mess and slower on Raspberry Pi OS than Chromium. I found Chromium a better browser experience than Firefox; Chromium is now my default browser.

That desktop screen capture you see above was taken with grim, a command line tool that is absolutely primitive to use and the only screen capture tool I found that worked. No other screen capture application will work because of the shift from X to Wayland. Basically it’s an all or nothing type of tool. If you want a specific section of the desktop, then you edit the full screen capture with another primitive graphics editing tool to whittle away the extraneous parts. For this post the full desktop was sufficient and required no further post processing.

After flipping back to Raspberry Pi OS and regretting the decision almost immediately, my intent is now to flop back to Ubuntu 23.10. For anything needing SPI support I’m going to move it over to one of my numerous microcontroller boards, such as one of the ESP32-S3 development boards. I can either code something in C++, or drop MicroPython on it. There’s a certain irony in doing a write/port to MicroPython as it won’t work with regular Python 3 under Ubuntu 23.10. But everything else works, and I might even cobble something together to use Bluetooth to communicate from the Raspberry Pi 5 to the ESP32-S3 hosting the MAX7219/1088AS displays. That sounds a lot more productive and a lot less frustrating than trying to beat Raspberry Pi OS into shape.

Yep. That’s my plan.

update to max7219/raspberry pi circuit

whbeebe
Schematic diagram

It bothered me quite a bit that my last few schematic diagrams were missing the 8×8 LED matrix display. As it turns out, the part number for the 8×8 LED display is printed on the side: 1088AC. When I went looking for any part sheets for it, all I found was a single page with this printed on it

1088AS schematic diagram

It was a PDF with a copy of a copy of the circuit diagram. I could barely make out the column, row, and physical pin numbers. I then went looking for an open source KiCad part for the 1088AC and found one on GitHub, which I forked and then cloned from my fork. I was able to quickly ascertain that the part was designed for KiCad 6. From there I used KiCad’s part library manager to import the part and then convert to KiCad 7 format. I had to do a bit more work with it before I could use it. For example, all the LED symbols were reversed, pointing up (as common anode) instead of down (common cathode). A little work to select and flip each diode symbol took care of that. I also change all the row pins from input to output, as they were all defined as input.

I am aiming to order a dozen or so MAX7221 parts from e-bay. The MAX7221 has a few additions internally over the MAX7219, one of which is that it support QSPI format data communications. Same price as the MAX2719, same pinout.

MAX7219/MAX7221

What’s interesting about the MAX7219/MAX7221 part sheet, it mentioned on the front page that it was suitable for LED matrix displays, but all the circuit diagram examples only show seven-segment by eight character displays, such as the one on the right above.

More learned with KiCad 7; better control with the schematic diagram, the ability to import parts, and the ability to convert from KiCad 6 to KiCad 7. When I’m finished with the 1088AC KiCad drawing part I’ll update my GitHub version and post a link to it in another post.

Links

My copy with updates and migration to KiCad 7. Note that only the 1088AS part has been updated. — https://github.com/wbeebe/kicad-LED_DotMatrix