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CFA633 key activity report


New member
I'm having a problem with the CFA633-TMC-KS keypad.
when I'm pressing the UP DOWN and EXIT key together I receive these key
activity reports:
0x80, 0x01, 0x01, 0x71, 0xC2 - key UP pressed
0x80, 0x01, 0x02, 0xEA, 0xF0 - key DOWN pressed
0x80, 0x01, 0x03, 0x63, 0xE1 - key LEFT pressed
0x80, 0x01, 0x06, 0xCE, 0xB6 - key EXIT pressed

and when I release the buttons I receive:
0x80, 0x01, 0x07, 0x47, 0xA7 - key UP released
0x80, 0x01, 0x08, 0xB0, 0c5F - key DOWN released
0x80, 0x01, 0x09, 0x39, 0x4E - key LEFT released
0x80, 0x01, 0x0C, 0x94, 0x19 - key EXIT released

I do not understand where the LEFT key come up because I didn't press it.

this happens all the time.

I checked that when I'm pressing every key in separate I have the correct key pressed and I do not receive additional reports.
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CF Tech

This is an artifact of keyboards that are read by scanning a matrix. The 633 uses a 2 x 3 matrix to scan its keys. As you get more keys pressed, the whole matrix becomes shorted, and then it is indeterminate which keys are pressed.

I believe that any 2-key combination should scan correctly, and some three key combinations (if they all fall on the same row) will read correctly.

Here is an experiment you can try on your PC. Open up notepad, and press and hold 'q', 'a', and 'z'. Then while still holding those, additionally press 'w', 's', and 'x'. On the two machines I tried, at least some of the keys were not detected. And that's with the PC's keyboard controller, which is much more sophisticated than the one in the 633. :)


New member

Thanks for the fast respond.
Can you give me some more detailed information of the keyboard matrix and the scan mechanisim so I will now what is the allowed combination.

Is it perfectly safe to work with a key combination of two or you suggest to avoid combination at all.

Eran Gez