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authorJoel Challis <[email protected]>2024-05-30 10:00:28 +0100
committerGitHub <[email protected]>2024-05-30 10:00:28 +0100
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parent6ef97172889ccd5db376b2a9f8825489e24fdac4 (diff)
downloadqmk_firmware-b39285807e1d21300e8a5dbbf6f2c43a8aab3494.tar.gz
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[docs] Fix code blocks overflowing page width (#23829)
Fix code blocks overflowing page width
Diffstat (limited to 'docs/how_a_matrix_works.md')
-rw-r--r--docs/how_a_matrix_works.md40
1 files changed, 28 insertions, 12 deletions
diff --git a/docs/how_a_matrix_works.md b/docs/how_a_matrix_works.md
index ebe90eb3de..fdd8c2d76f 100644
--- a/docs/how_a_matrix_works.md
+++ b/docs/how_a_matrix_works.md
@@ -6,6 +6,7 @@ When the circuit is arranged in rows and columns, if a key is pressed, a column
The microcontroller will be set up via the firmware to send a logical 1 to the columns, one at a time, and read from the rows, all at once - this process is called matrix scanning. The matrix is a bunch of open switches that, by default, don't allow any current to pass through - the firmware will read this as no keys being pressed. As soon as you press one key down, the logical 1 that was coming from the column the keyswitch is attached to gets passed through the switch and to the corresponding row - check out the following 2x2 example:
+```
Column 0 being scanned Column 1 being scanned
x x
col0 col1 col0 col1
@@ -13,11 +14,13 @@ The microcontroller will be set up via the firmware to send a logical 1 to the c
row0 ---(key0)---(key1) row0 ---(key0)---(key1)
| | | |
row1 ---(key2)---(key3) row1 ---(key2)---(key3)
+```
The `x` represents that the column/row associated has a value of 1, or is HIGH. Here, we see that no keys are being pressed, so no rows get an `x`. For one keyswitch, keep in mind that one side of the contacts is connected to its row, and the other, its column.
When we press `key0`, `col0` gets connected to `row0`, so the values that the firmware receives for that row is `0b01` (the `0b` here means that this is a bit value, meaning all of the following digits are bits - 0 or 1 - and represent the keys in that column). We'll use this notation to show when a keyswitch has been pressed, to show that the column and row are being connected:
+```
Column 0 being scanned Column 1 being scanned
x x
col0 col1 col0 col1
@@ -25,16 +28,20 @@ When we press `key0`, `col0` gets connected to `row0`, so the values that the fi
x row0 ---(-+-0)---(key1) row0 ---(-+-0)---(key1)
| | | |
row1 ---(key2)---(key3) row1 ---(key2)---(key3)
+```
We can now see that `row0` has an `x`, so has the value of 1. As a whole, the data the firmware receives when `key0` is pressed is:
- col0: 0b01
- col1: 0b00
- │└row0
- └row1
+```
+col0: 0b01
+col1: 0b00
+ │└row0
+ └row1
+```
A problem arises when you start pressing more than one key at a time. Looking at our matrix again, it should become pretty obvious:
+```
Column 0 being scanned Column 1 being scanned
x x
col0 col1 col0 col1
@@ -44,16 +51,20 @@ A problem arises when you start pressing more than one key at a time. Looking at
x row1 ---(key2)---(-+-3) x row1 ---(key2)---(-+-3)
Remember that this ^ is still connected to row1
+```
The data we get from that is:
- col0: 0b11
- col1: 0b11
- │└row0
- └row1
+```
+col0: 0b11
+col1: 0b11
+ │└row0
+ └row1
+```
Which isn't accurate, since we only have 3 keys pressed down, not all 4. This behavior is called ghosting, and only happens in odd scenarios like this, but can be much more common on a bigger keyboard. The way we can get around this is by placing a diode after the keyswitch, but before it connects to its row. A diode only allows current to pass through one way, which will protect our other columns/rows from being activated in the previous example. We'll represent a dioded matrix like this;
+```
Column 0 being scanned Column 1 being scanned
x x
col0 col1 col0 col1
@@ -65,11 +76,13 @@ Which isn't accurate, since we only have 3 keys pressed down, not all 4. This be
(key2) (key3) (key2) (key3)
! ! ! !
row1 ─────┴────────┘ row1 ─────┴────────┘
+```
In practical applications, the black line of the diode will be placed facing the row, and away from the keyswitch - the `!` in this case is the diode, where the gap represents the black line. A good way to remember this is to think of this symbol: `>|`
Now when we press the three keys, invoking what would be a ghosting scenario:
+```
Column 0 being scanned Column 1 being scanned
x x
col0 col1 col0 col1
@@ -81,13 +94,16 @@ Now when we press the three keys, invoking what would be a ghosting scenario:
(key2) (┌─┘3) (key2) (┌─┘3)
! ! ! !
row1 ─────┴────────┘ x row1 ─────┴────────┘
+```
Things act as they should! Which will get us the following data:
- col0: 0b01
- col1: 0b11
- │└row0
- └row1
+```
+col0: 0b01
+col1: 0b11
+ │└row0
+ └row1
+```
The firmware can then use this correct data to detect what it should do, and eventually, what signals it needs to send to the OS.