Electronic – Displaying ASCII codes to an 7×5 LED Matrix


I want to know the best way to display ASCII binary code to a 7×5 LED matrix (cathode). The way I'm thinking to approach right now involves an decoder for each column (containing 7 bits, regarding the lines), and a multiplexer that receives the 35 decoded entries and outputs 7 bits. There is also a shift register in the same clock as the MUX to set HIGH in the columns the multiplexer set LOW the lines that are supposed to light. I wonder if that is the best way to do this, considering that the column decoder would be huge. Thanks for your time!
PS. Also, I forgot to mention, I am using a FPGA for this project
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Best Answer

  • There is no best way without specifying constraints.
  • Assuming you are only making 1 unit, the BOM cost is likely second after feature flexibility.
  • Embedded processor provide flexibility far greater than combinational logic.

Normally, LED matrix displays such as these are not all tied to 1 common cathode. Rather, they are arranged in a matrix:

enter image description here

Most embedded processors have enough programmable GPIO pins to drive such a display. Here is a project in which an Atmel embedded processor (Arduino) is used to drive an 8 x 8 LED matrix.

Once built, you can program the embedded processor to display your ASCII data in any number of ways. As 5 binary 7 bit numbers in each of the 5 vertical columns. As a graphical character as defined by this table:

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Since an embedded processor is being used, you imagination is free to create any pattern to represent your data.

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