08 · Switches, keys, LEDs and the 7-segment display

The board's own inputs and outputs, done properly: debounced switches and keys, a press counter in decimal, and text scrolling across the six digits.

The repo keeps the full project (.qar, plus the sources here) but no prebuilt bitstream: one build (a few minutes) makes the .sof on your computer.

What you will see

Your PC (python scripts/de10.py log): SW=3FF, KEY0 down count=000005, KEY1 down: reset.

Block diagram

The parts

All pins are in lib/board/de10_lite_pins.csv; scripts/new_project.py assigns them from your top module's port names.

Showing text: seg7_char

seg7_char c(.ch("E"), .dp(1'b0), .seg(HEX5));     // any ASCII: digits, most letters, - _ =

lib/rtl/seg7_char.sv turns an ASCII character into segments: digits, the letters that have a fair 7-segment shape (A b C d E F G H I J L n o P q r S t U y), and a dash for the rest. Numbers in decimal: bin2bcd then 8'h30 + digit.

Counting presses: debounce, then an edge

debounce #(.N(12), .STEADY(500_000)) deb(.clk(clk), .in({~KEY, SW}), .out({key_down, sw}));  // 10 ms
always @(posedge clk) key_d <= key_down;
wire [1:0] press = key_down & ~key_d;     // one clock per press

Without the debounce a single press often counts 2 to 5 times.

Measured on the board

• Text mode (all switches up): the camera shows the message moving ("o dE10", then "E10-LI" a second later) and the running light.
• USB: SW=3FF at start-up.
• Resources: 1,715 logic elements (3 %). Timing: no negative slack.

Count mode (SW9 down, KEY0 / KEY1) needs someone at the board; it is still to be checked by hand.

Run it

python scripts/de10.py build examples/08_board_io
python scripts/de10.py program examples/08_board_io
python scripts/de10.py log 30

Build it yourself

python scripts/new_project.py examples/08_board_io board_io_top --lib print debounce bcd seg7
python scripts/de10.py build examples/08_board_io

Files