KEY MATRIX 4x4

Specification

What		Comments
Identifier	KEY_MATRIX_4_4
Interface	8 GPIO	GPIO 1: L1 GPIO 2: L2 GPIO 3: L3 GPIO 4: L4 GPIO 5: H1 GPIO 6: H2 GPIO 7: H3 GPIO 8: H4 Lx: columns Hx: rows
Provides	key1 key2 key3 key4 key5 key6 key7 key8 key9 key10 key11 key12 key13 key14 key15 key16	1 = key down 0 = key up
Properties	repeat	1 = enable repeat function, 0 = disable. When enabled this sensor fires a callback when you press and hold a key on the key matrix.
	repeat delay	When you press and hold a key on the key matrix, the sensor fires a callback. The pause between pressing the key and when it starts repeating is the repeat delay, expressed in msecs. Default value is 1500 msecs.
	repeat rate	After you press and hold down a key on the key matrix, the key starts repeating once the repeat delay expires. The speed at which it repeats is the repeat rate, expressed in msecs. Default value is 500 msecs.
Callbacks?	yes

Notes

• This sensor requires 8 GPIO. We recommend to use an external GPIO with pull-ups like the PCA9505 chip.
• This sensor performs a scan on the entire key matrix every 1 msec. You can find the operating principle in this article.
• Hardware pull-ups are not required.
• Many cheap key matrix don't include diodes for each key, so you may experiment ghosting and masking problems if you use these key matrix.
• You can use key matrix with diodes with this sensor.

Code

-- Attach the key matrix using an external GPIO chip
km = sensor.attach("KEY_MATRIX_4_4", 40, 41, 42, 43, 44, 45, 46, 47)

km:callback(
   function(data)
      if (data.key1 == 1) then
         print("key1")
      end

      if (data.key2 == 1) then
         print("key2")
      end

      if (data.key3 == 1) then
         print("key3")
      end

      if (data.key4 == 1) then
         print("key4")
      end

      if (data.key5 == 1) then
         print("key5")
      end

      if (data.key6 == 1) then
         print("key6")
      end

      if (data.key7 == 1) then
         print("key7")
      end

      if (data.key8 == 1) then
         print("key8")
      end

      if (data.key9 == 1) then
         print("key9")
      end

      if (data.key10 == 1) then
         print("key10")
      end

      if (data.key11 == 1) then
         print("key11")
      end

      if (data.key12 == 1) then
         print("key12")
      end

      if (data.key13 == 1) then
         print("key13")
      end

      if (data.key14 == 1) then
         print("key14")
      end

      if (data.key15 == 1) then
         print("key15")
      end

      if (data.key16 == 1) then
         print("key16")
      end
   end
)

Back to sensor list