[J-core] Simple introductory project - Numato board 7-segment display

Rich Felker dalias at libc.org
Wed Oct 12 14:12:39 EDT 2016

While debugging some actual work on the Numato Mimas v2 board, I
happened to look up how the 7-segment leds work. Their usefulness is
limited by the fact that there are only 8 actual gpio pins controlling
the segments for all 3, along with an enable pin for each digit,
meaning each digit has to be off or displaying the same content as the
other active digits.

In principle it should be possible to add a small bit of vhdl that's
clocked to cycle which digit is enabled, reading from a 12 bit
register storing the desired contents for all three. In many ways this
is like primitive video scan (like what you'd do for vga) and would be
a both a good exercise for getting started on that type of design with
immediate results, and a useful tool to have around for debugging.


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