Datasheet
EA eDIPTFT70-A
Page 9
ELECTRONIC ASSEMBLY reserves
the right to change specifications
without prior notice. Printing and
typographical errors reserved.
EXTERNAL KEYBOARD
A keyboard (anything from individual keys to a 8x8 matrix keyboard) can be connected to the I/O- ports.
The command ‘ESC Y M n1 n2 n3’ defines the count of input lines (n1=1..8) and output lines (n2=1..8).
n3 set debounce function with 10ms steps (n3=0..15). Please note that count of digital input and output
lines will be reduced while connecting an external keyboard at the same port.
Each key is connected with 1 output and 1 input. All inputs are terminated with a 20..50kΩ pull-up
resistor. For double-keystroke function decoupling of outputs is necessary. For that please use
schottky diodes (e.g. BAT 46).
Transmitting the keystrokes
At each keystroke, the associated key number (1..64) is transmitted or if a corresponding Matrix-
Macro is defined, Matrix-Macro will be started. The release of the key is not transmitted. If the release
of the key is to be transmitted as well, this can be done by defining Matrix-Macro no. 0.
(see page 21: Responses of EA eDIP)
Calculating of key numbers:
2x2 Matrix 1x4 Matrix 4x0 Matrix 4x4 Matrix
Key_number = (output-1) * count_of_inputs + input (output = MOx, input = MIx).
Examples
- 2x2 matrix: Command ‘ESC Y M 2 2 ..’ defines the 2x2 matrix. Keypad will need input lines MI1, MI2
and output lines MO1, MO2. Output lines are decoupled by diodes; this is for double
keystrokes necessary. 6 input and 6 output lines remain free for other requirements.
- 1x4 matrix: Command ‘ESC Y M 1 4 ..’ defines the 1x4 matrix. Keypad will need output lines
MO1..MO4 and a single input line MI1. With that connection 7 input and 4 output lines
remain free for other requirements.
- 4x0 matrix: Using one single output only (physically 4x1 Matrix), all keys can switch to GND. So no
output line is necessary and command ‘ESC Y M 4 0 ..’ defines 4 input lines onyl. With
that connection 4 input and 8 output lines remain free for other requirements.
- 4x4 matrix: Command ‘ESC Y M 4 4 ..’ defines the 4x4 matrix. Keypad will need input lines MI1..MI4
and output lines MO1..MO4. Output lines are decoupled by diodes; this is for double
keystrokes necessary. 4 input and 4 output lines remain free for other requirements.
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