Pingaso: /* ECS Keyboard */

2012-04-02T03:30:24Z

‎ECS Keyboard

Pingaso at 00:32, 1 April 2012

2012-04-01T00:32:42Z

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Mr z: Protected "Entertainment Computer System" ([edit=autoconfirmed] (indefinite) [move=autoconfirmed] (indefinite))

2010-12-04T08:20:49Z

Protected "Entertainment Computer System" ([edit=autoconfirmed] (indefinite) [move=autoconfirmed] (indefinite))

Mr z at 08:20, 4 December 2010

2010-12-04T08:20:37Z

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 That gives you a basic matrix-scanned keyboard. Here's a simple example of a 3x3 keyboard with the keys A through I. (Note: This is just meant to be an example; it is not the actual ECS keyboard matrix.)
-Posted Image
+[[Image:simple_3x3.png]]
 When you press 'A' in this example keyboard, it connects Row 0 to Col 0. When you press 'I', it connects Row 2 to Col 2.
@@ Line 53: / Line 53: @@
 Let's say you press A and E at the same time. When you scan Row 0, you'll see Col 0 light up, and when you scan Row 1, you'll see Col 1 light up, as in the following diagrams.
-Posted Image Posted Image
+[[Image:Simple 3x3 A and E row0.png]]
 So far, so good. Now what happens when you also press B in addition to A and E? Let's scan Row 0:
-Posted Image
+[[Image:Simple 3x3 A B and E row0.png]]
 We light up Row 0, and both Col 0 and Col 1 light up as we expect. But, the fuschia line above shows another line that gets lit up... Row 1! So far, that hasn't caused a problem. But if your Spidey Sense is tingling, telling you that things are about to go horribly wrong, you'd do well to listen to it. Let's scan Row 1 and watch it go pear shaped:
-Posted Image
+[[Image:Simple 3x3 A B and E row1.png]]
 Since we've only pressed E in Row 1, we only want to see Col 1 light up. But, because the switches at B and A are also closed, we also have a complete circuit to Col 0, so both Col 0 and Col 1 light up. It looks to us as if both D and E are pressed at the same time. Oops!
@@ Line 72: / Line 71: @@
 With diodes, the keyboard matrix looks like this:
-Posted Image
+[[Image:Simple 3x3 diodes.png]]
 Now if we press A, B and E, everything works like you expect, because the diodes block the ghost paths:
-Posted Image Posted Image
+[[Image:Simple 3x3 diodes A B and E row0.png]]
 Even though B lights up when we light up Row 1, the diode prevents that from inadvertently lighting up Row 0 and flowing (via the switch at A) to Col 0.
@@ Line 84: / Line 83: @@
 Both ECS keyboards are basic matrix scanned keyboards. The alphanumeric keyboard is a simple 48-key matrix with no diodes. There are 49 actual keys, but the "Shift" keys are wired to the same row/column in the matrix. If you press the wrong keys at the same time, you will see ghosting. The following diagram gives the matrix for this keyboard:
-Posted Image
+[[Image:Ecs keyboard matrix.png]]
 You'll notice Row 6 only has the shift key, and Row 7 is empty. Also, there's no key associated with Row 0/Col 7.

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