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By bigglez
Lucien wrote: On the subject of "viewable from the rear", I've seen some SMD LEDs made for reverse mounting, where the LED is meant to shine through a hole in the PCB between the pads. I think they were made by Avago.
Greetings Lucien,

The brand I'm using are Lite-On LTST-C150KRKT (Digikey PN
160-1405-1-ND), and are available as rear mount LTST-C230CKT
(Digikey PN 160-1186-1-ND). This creates more options!
Lucien wrote: Would a 7x9 be doable with the 7219/7221? I wouldn't have thought you'd be able to swap the function of a line around on these chips.
Sure, the array is 8x8 or 64 separately driven LEDs. They can be
placed physically in any pattern. A 7x9 (63 LEDs) would require a
LUT to map the ASCII data to a font that lights the right LEDs.

I'm thinking of doing a 2:1 aspect array, originally 16 x 8, but
now 14 x 9 to have two characters that can scroll left and right.
There might be some merit to divider column or two between the
characters, but that really throws the math off for the MAX
drivers. However, 16 is a binary friendly number, so perhaps
logic shift registers for the columns make more sense?

I'm heading towards a two-digit clock, HH blank MM sequence.

Comments Welcome!
User avatar
By ohararp
Hey all I just wanted quickly bump this thread and show my Blue Led Matrix Backpack design. These module are cool because I can link up to 16 (max tested so far) together very easily. You can checkout the youtube vid for more details

The video is a little jittery (sh$% camera) and is a simple demo of the font. I have a breadboard control using an xbee transceiver for wireless message updates. I also included an RTC and a temp sensor for other message data.

Overall the MAX7219 is a great chip!

User avatar
By bigglez
ohararp wrote:Hey all I just wanted quickly bump this thread and show my Blue Led Matrix Backpack design.
Congrats on the project! Very timely, too, as there
is an interesting article in Circuit Cellar issue 221 and
on their forum. (Also discussion of photgraphing these beasts,
too). The project is called Puzzlemation. here's a Youtube vid.