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GCA128L pushbutton testboard for I/O units


By Peter Giling


The board connects with the standard 10 Pin PSK connecter to the GCA50, CAN-GC2 or GCA_PI02 and WIO Modules.
Two connectors are provided, which are internally connected together.
This enables the use of GCA128L in between the testing area.
It fits in a standard LDT-1 box
The interface is set-up as a test-unit for any of the I/O units in the various systems.
Each button is connected via a resistor to a port.\ These resistors will avoid that the port under test will get damaged when in output state.
At any port, when it is activated as output, pressing the button has no effect.
GCA128L is provided with Bus driver 74HC245.
This makes sure that leds give a real picture of the logical state the I/O ports are in.
Free unactivated inputs will always show with green led, because a free input is always in high state.

Using the board with 3.3V I/O

The partslist indicates the use of an octal bus driver chip 74HC245.
That chip is not useable with 3.3 V I/O ports.
Replacing the chip with 74HC245, and the unit will be able to handle 2 to 6 Volt.
Future kits will have 74HC245 standard.

Led indication

Red and green leds of each port are interconnected in a way that when port = high, green led shows,
and when port is low, red led is lit.
In case a port is set to output, pushbutton is inactive.

Led indication truth table.
PORT colour
1 3 HIGH* green
1 3 LOW red
2 4 HIGH* green
2 4 LOW red
3 5 HIGH* green
3 5 LOW red
4 6 HIGH* green
4 6 LOW red
5 7 HIGH* green
5 7 LOW red
6 8 HIGH* green
6 8 LOW red
7 9 HIGH* green
7 9 LOW red
8 10 HIGH* green
8 10 LOW red
Ports Indicating HIGH in table above could also be set as INPUT.

*) In case of pushbutton not showing any effect, the port is set to output.

Please consider that portnumbers are strictly related to pin numbers of the board under test.

The hardware

This board is available, also as kit, without box.

N.B. Only complete ordered kits are supported!


Connector J1 and J2 are interconnected.
This enables the use of GCA128L in between the I/O unit and any Input/Output driver.

mgv128-en.txt · Last modified: 2023/05/16 19:18 by phg