Teensy 2.0 Row and columns
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Theremingenieur
Senior Member+
If I understand well, you want to read a button matrix with your Teensy. In that case, it is up to you as the software developer to define which pins output signals to the columns and which pins read signals from the rows (or the other way round), and to write the corresponding code.
You might google around to find a button matrix library if you prefer using prefabricated code. There is one for the Teensy, but I‘m not sure if it is compatible to the older Teensy 2.x series.
You might google around to find a button matrix library if you prefer using prefabricated code. There is one for the Teensy, but I‘m not sure if it is compatible to the older Teensy 2.x series.
el_supremo
Well-known member
How big a matrix are you using?
Pete
Pete
Theremingenieur
Senior Member+
First, one would have to define the number of buttons which would have to be read. Often, the Teensy 2.0++ or the Teensy 3.5/6 have enough pins to read many buttons directly, without matrix, depending on the number of pins which you‘ll perhaps need afterwards for other functionalities. If you really must go for a matrix, you trade less used pins for more complex code. So, for 20 buttons, you would not longer need 20 pins, but only 9 (4 cols x 5 rows).
A matrix consists of rows and columns and the buttons are wired in a way that each button, when pressed, connects exactly one column wire with one row wire. Now comes the code side: In a loop, the column wires will be driven high for a short interval (i.e. 20ms) and then again low, one after the other, in a cyclic way. Each time, one column wire is driven high, all row pins will be read to see if one of the buttons in this columns is pressed. From the number of the actual high column and the row pin which is driven high, the code will know which button is pressed and can invoke any action which is intended to happen whet his specific button is pressed.
Basically, it‘s relatively simple - no black magic! In reality, after a button press is detected, your code would first check if that button was already pressed during the last column cycle, to prevent repeated triggering. That‘s all.
A matrix consists of rows and columns and the buttons are wired in a way that each button, when pressed, connects exactly one column wire with one row wire. Now comes the code side: In a loop, the column wires will be driven high for a short interval (i.e. 20ms) and then again low, one after the other, in a cyclic way. Each time, one column wire is driven high, all row pins will be read to see if one of the buttons in this columns is pressed. From the number of the actual high column and the row pin which is driven high, the code will know which button is pressed and can invoke any action which is intended to happen whet his specific button is pressed.
Basically, it‘s relatively simple - no black magic! In reality, after a button press is detected, your code would first check if that button was already pressed during the last column cycle, to prevent repeated triggering. That‘s all.
Once I learn I can make that magic.
Theremingenieur
Senior Member+
As I told you, start with a library like this one (which is already included in the Teensyduino installation) : https://www.pjrc.com/teensy/td_libs_Keypad.html
The example shows a 3 x 4 matrix which you might adapt to your needs.
The example shows a 3 x 4 matrix which you might adapt to your needs.
PaulStoffregen
Well-known member
In Arduino (with Teensyduino installed), first make sure Teensy is selected in Tools > Boards, because the other Arduino menus update depending on the board selected.
The click File > Examples > Keypad > HelloKeypad. Even if your keypad has more wires, connect 4 of its rows to pins 2-5 and 3 of its columns to pins 6-8 and run the example. Open the serial monitor, press all the buttons and what when prints in the serial monitor. When you get that working, hopefully you'll see a path forward to edit the example for more rows or columns.
The click File > Examples > Keypad > HelloKeypad. Even if your keypad has more wires, connect 4 of its rows to pins 2-5 and 3 of its columns to pins 6-8 and run the example. Open the serial monitor, press all the buttons and what when prints in the serial monitor. When you get that working, hopefully you'll see a path forward to edit the example for more rows or columns.
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