HDSP-211x for Raspberry Pi

On the project page about using LED matrix displays of the type HDSP-212x, I also showed an example setup with a Raspberry Pi. Now that I still have some of these displays, I would like to use them to build a real device in its own case.

Soldering the whole thing by hand on a perfboard would theoretically be possible, but is prone to errors and in the end you have only one copy. Nowadays there is a better solution for this: you design a circuit board with a program like KiCad and have it produced as a small series for comparatively little money.

My first draft for a board on which you can put four HDSP-211x next to each other already looks quite promising:

At AISLER, the production of three copies would cost around EUR 25 and would be ready in about a week. But before I actually do this, I’ll have to check the circuit diagram again and check whether adjustments are required for the power supply, since four modules together can have a power consumption of more than 1.6 A.

Revision 2

After taking a closer look at KiCad, I created a revised revision 2 of the layout:

  • The total size of the board is a bit smaller.
  • The mounting holes are now inserted as footprints and without soldier mask.

Controlling a HDSP-2112

“I’ve created fire!”

The HDSP-2112 is a module with a LED matrix display which displays 8 characters with 5×7 LEDs each. Due to the high power requirement of more than 2 watts this display is not suitable for mobile devices. The operating voltage is 5 volts and it will be controlled using a 8 bit wide data bus and a 5 bit wide address bus.

I already experimented with this in 2013, however I stopped working on that and did not have a working setup ever.

This time I was more persistent – and it worked :-).

HDSP-2112, test with Raspberry Pi

More about this along with a thorough documentation on the project page.

By the way – about USB controllers

My PC is built into a tower case from Chieftec. This case offers also external ports for USB 3 among other things. Internally, these ports are connected to the mainboard.

However, I also installed an internal memory card reader from Chieftec, which also uses USB 3 and offers a 4× USB hub. This means that the only internal USB 3 port on the mainboard is occupied. In order to be able to use the external USB connections, I bought an additional controller for PCI-Express, which offers two external USB connections and two more internal connections. The connections in the housing can also be supplied via this.

So far so good – but there was a strange effect when I tried to use a Velleman K8055N: as soon as the connection was established in the software, the software stopped working. This effect did not occur using the connections of the mainboard itself. The USB connections of the memory card reader were not a problem either.

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Juan Joya Borja is dead

The spanisch comedian Juan Joya Borja, who is also known as “Risitas” or “El Risitas” – “the giggling”, has died at the age of 65 in a hospital in it’s hometown Sevilla according to a report in the spanish media.

Juan Joya Borja became famous by a video meme which was used in many variations with different subtitles:

Signal wants to integrate “Mobile Coin”

I advertised the use of Signal already in 2019 and was quite happy that many of my contacts changed to Signal as well when WhatsApp announced a mandatory change in their terms of use at the beginning of 2021.

Now Signal decided to integrate the crypto currency “Mobile Coin”. Moxie Marlinspike works as a paid consultant for Mobile Coin, so this is not really a surprise. Nevertheless I consider this questionable and I am not alone with this impression.

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Caveats of the fullscreen API

My example for WebGL and the monitor test use a canvas element for display. In addition there is an option to switch to fullscreen mode. Technically this is achieved by using the fullscreen API. The implementation is always the same:

  1. When clicking the button fullscreen mode the canvas element will be changed to fullscreen by using requestFullscreen().
  2. A handler which reacts to fullscreen changes corrects the width and height of the element to the screen size taking window.devicePixelRatio into account to support the native resolution of the device.

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OnlyOffice in Nextcloud – the current status

I recently reported hastily that OnlyOffice in Nextcloud would generally no longer work properly.

However, this is generally not correct and I did premature conclusions for some points. Ascensio System also got in touch with me and did everything possible to help me with my problems – thank you!

I removed the original post because it was based on incorrect assumptions.

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