5

EA KIT320-8

Type 1: 2x2 Matrix

Type 2: 1x4 Matrix

Type 3: 4x0 Matrix

EXTERNAL MATRIX KEYBOARD

A matrix keyboard (anything from individual keys to an 8x8 matrix keyboard) can be connected at the

plug-in connection J120. The number of inputs and outputs of the ports (n1,n2=1..8) used is defined

and the key debouncing is specified (n3=0..7 in 50ms increments) by means of the ‘ESC Y M n1 n2

n3’ command. Please note when an external keyboard is connected that the digital inputs are reduced

by the number n1 and the outputs are reduced by the number n2.

Each key is generally switched between an output and an input. Each input has a 100k

Ω (approx.)

pullup. In order to identify double keystrokes, the outputs must be decoupled from each other. This

is best done with Schottky diodes (e.g. BAT 43).

Transmitting the keystrokes

At each keystroke (key number 1..64), the associated matrix macro is executed or, if no macro is

defined, the key number is transmitted with code letters. 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.

Note If the CTS handshake line does not permit transmission, up to 8 keystrokes are stored in the

key buffer. When the buffer is full, older keystrokes may be lost.

Determining the key number:

Key no. = (output no. - 1) * no. of inputs + no. of outputs

(output = MOx, input = MIx).

Example: Connection of 4 keys in 3 variations

- Variant 1:

The 4 keys are defined as a 2x2 matrix by means of the ‘ESC Y M 2 2 ..’ command.

The keys are connected to 2 inputs (MI1, MI2) and 2 outputs (MO1, MO2). The

outputs are decoupled from each other by means of diodes so that double

keystrokes can be identified. There are 6 inputs and 6 outputs available as port

connections.

- Variant 2:

The 4 keys are defined as a 1x4 matrix by means of the ‘ESC Y M 1 4 ..’ command.

The keys are connected to 4 outputs (MO1, MO2) and read in via input MI1. There

are 7 inputs and 4 outputs available as port connections.

- Variant 3:

If only one output is used (4x1 matrix), the keys can also be connected to ground

and read in directly at the inputs (= 4x0 matrix). The 4 keys are defined at the 4

inputs (MI1..MI4) by means of the ‘ESC Y M 4 0 ..’ command. There are 4 inputs

and 8 outputs available as port connections.