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--- switches_as_digital_inputs [2018/12/11 22:29] – created tell
+++ switches_as_digital_inputs [2018/12/11 22:42] (current) – tell
@@ Line 11: / Line 11: @@
 We could use two DIOs for two different limit switches: one for UP, one for DOWN, and if neither switch is closed, we interpret that to mean the mechanism is somewhere in between.
+===== Autonomous Selection =====
 Suppose we want to select from four different autonomous routines.  we could use two switches, and tell the drive team to set them according to a table like this:
@@ Line 17: / Line 19: @@
   * 1: Closed, Open   - drive forward
   * 2: Open, Closed   - drive forward and place power cube
-  * 3: Closed, Closed - drive forward, turn left, drive, turn right, drive, and then place cube
+  * 3: Open, Open - drive forward, turn left, drive, turn right, drive, and then place cube
-[picture]?
+Given three switches and 3 digital I/Os, we could chose from 8 alternatives.  The eastbots actually did this on our [[2018 Season]] practice robot:
-But requiring the drivers to read the chart, even if it is written on the robot, is error prone.
+{{ :auto-select-binary.jpg?300 |}}
-A better **user interface** would be a rotary switch.
-[picture]
+But requiring the drive team to read a chart and set several switches, even if the chart is written on the robot, could be confusing in the heat of the match and error prone.
+A better **user interface** would be a rotary switch, which we used on our 2018 competition robot.
+{{ :auto-select-switch.jpg?400 |}}
 A typical rotary switch contains one or more "levels" each with a moving contact that can connect to one fixed contact at a time.  We typically draw the schematic for such a switch like this:
@@ Line 33: / Line 38: @@
 {{ :rotary-binary2.png?nolink |}}
+====== More switch ideas ======
+Suppose there were only three autonomous choices.  One three-position toggle switch could control two DIOs.
+Such a switch is called a "single pole, double-throw, center off" switch.  The switch, and its schematic symbol look like:
+[picture]
+Notice how the body of the switch is labled "on-off-on."  This how to tell that it has a center-off position without even moving the lever.   We wired it up like this:
+[picture]