Hi

Couldn't find a decent schematic for a matrix keyboard, so I invented my own.
I soldered the pull-up resistors on the board before coding, so that's why the
negative logic. With pull down resistors you can have positive logic.
I should be a function too, but I'm from the FORTRAN dark ages with huge
"common blocks".

Anyway, here it is:

--
-- file      : keyb.jal
-- author    : Eur van Andel, eur@fiwihex.nl
-- date      : 24-01-2002
-- purpose   : matrix keyboard routine
-- requires  : -
--
-- Matrix keyboard connections
--
--      1  2  3  --- D0   row lines connected to D0...D3 PIC pins
--      4  5  6  --- D1
--      7  8  9  --- D2
--      *  0  #  --- D3
--
--      |  |  |
--      D4 D5 D6   column lines connected to D4..D6 PIC pins
--      |  |  |
--      /  /  /  10k pullup resistors
--      \  \  \
--      |  |  |
--      |__|__|___ +5V
--
--
--  keyb.jal gives you a global byte variable called key that
--  will take the value of the key you press, *=10, #=11
--  feel free to modify procedure keyboard to a function
--
--
-- Blah, GNU, blah
--

var bit R1 is pin_d0    -- row wires are outputs
var bit R2 is pin_d1
var bit R3 is pin_d2
var bit R4 is pin_d3
var bit C1 is pin_d4    -- column wires are inputs, pulled-up  with 10K
var bit C2 is pin_d5
var bit C3 is pin_d6

pin_d0_direction = output
pin_d1_direction = output
pin_d2_direction = output
pin_d3_direction = output
pin_d4_direction = input
pin_d5_direction = input
pin_d6_direction = input

var byte key

procedure keyboard is
port_d_low = 0b1110             -- 123 row low
if ! C1 then key = 1 end if
if ! C2 then key = 2 end if
if ! C3 then key = 3 end if
port_d_low = 0b1101             -- 456 row low
if ! C1 then key = 4 end if
if ! C2 then key = 5 end if
if ! C3 then key = 6 end if
port_d_low = 0b1011             -- 789 row low
if ! C1 then key = 7 end if
if ! C2 then key = 8 end if
if ! C3 then key = 9 end if
port_d_low = 0b0111             -- *0# row low
if ! C1 then key = 10 end if
if ! C2 then key = 0 end if
if ! C3 then key = 11 end if
end procedure


--
Ir. E.E. van Andel, Fine Wire Heat Exchanger Technology  www.fiwihex.com
Wierdensestraat 74, NL-7604 BK  Almelo, The Netherlands   eur@fiwihex.nl
phone +31-546-491106  fax +31-546-491107  mobile +31-653-286573

--
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